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Chapter 10 Amplifiers by pptfiles

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Chapter --: Amplifiers
Amplifiers (amp or amps) boost the volume and provide better sound quality. Adding
high-quality aftermarket speakers or component systems to the vehicle may require more
power than what the amp in an existing in-dash receiver provides.

The term “clean sound” or a “clean amp” is a reference to how clean an amp increases a
signal’s amplitude and sends it to the speakers. In other words, an amp is designed to
increase volume and not have any sound processing or noise generating effect on the
signal. Other terms like “warmth” or “precision” or “cool” are frequently used and are
highly subjective.

A channel is a complete amplifying stage in any audio amplifier. Amps come in 1, 2, 4,
5, or 6 channel configurations. Each channel is a discrete audio amp on its own, capable
of taking a line signal input and amplifying it sufficiently to be heard on a speaker. Some
amplifiers are capable of bridging two channels together, doubling the power on one
channel.

Channel balance refers to balance of left and right channels in a stereo system. When
balanced, the “stereo image” is centered between the left and right channels. In surround
systems, channel balance refers to all the channels (5.1, 6.1 or 7.1).

For subwoofers, a mono amplifier is used. Subwoofers are speakers specifically designed
to hand the low end of the sound spectrum (bass). They are often called just woofers or
subs. Mono amps are designed for low-frequency repoduction, with built-in bass boost
and low-pass filters.

A 2-channel amp can be used for powering two subwoofers, or “bridged” to a single
channel operation for a single woofer. Likewise, a 4-channel amp can be bridged to 2-
channel mode to power a pair of subs.

For full-range or component speaker systems, a 2 or 4-channel amplifier is used,
depending on the number of speakers to power. A 4-channel amp is used for a
combination of full-range speakers and subwoofers.

Another alternative with a 4-channel amp is to use 2 channels to drive a pair of full-range
speakers, and bridge the other 2 channels to power the subwoofer. Or, a 2-channel amp
with a tri-way “crossover” can power a pair of full-range speakers and a subwoofer.
Obviously, there are a number of different solutions.

Most amps will accept a signal from a brand-name receiver through its preamp inputs.
To accept a signal from a factory system, the amp needs speaker level inputs. With
speaker level inputs there is no need to mess with speaker wiring or special adapters.
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Amplifier power output matches the power handling of the speakers being amplified
(installed). Wattage is used my manufacturers to make comparisons, but “RMS” power
ratings are really the only way to determine amp and speaker power capability.

RMS (Root Mean Square) is a formula that provides a reasonably accurate means of
measuring and comparing continuous power. The use of this measure is preferred when
matching system components, like amplifiers, receivers and speakers. RMS Power is the
amount of continuous power measured in watts produced by an amplifier. The higher the
RMS figure, the louder and cleaner the music sounds.

In most cases, the power specification (wattage) must be divided by the number of
channels in the amp to determine the amount of power available to each channel. For
instance, a 100 watt rating for a 2-channel amp means 50 watts per channel. RMS values
are determined by dividing the wattage by 2.

Peak and Max specifications refer to the amount of power that a component can generate
or handle at any given moment. Stereo manufacturers often display peak power ratings
on the face of their products. The peak power rating tells the maximum wattage an
amplifier can deliver as a brief burst during a musical peak, like a dramatic drum accent.

RMS—continuous watts—indicate how much power can be exchanged on a constant
basis. Generally, RMS is half or less of the value usually attributed to alternative
methods such as Peak power, Max power, or Instantaneous Peak Power.

Power Handling is another specification indicating RMS—a rating of a speaker driver’s
ability in optimum conditions to handle a specified amount of audio power (electrical
current power) on a constant basis, without damage.

Some manufacturers calculate the RMS power ratings of their amplifiers at different
input voltages. For example, an amplifier rated at 100 watts RMS at 12 volts can produce
considerably more power than an amp rated at 100 watts RMS at 14.4 volts.



Amplitude
In physics and electronics, amplitude is literally the measurable high value of a
periodically varying quantity. In less technical terms, it is the strength of a signal or
sound, regardless of what kind of sound it is. Amplitude measurements of audio signals
generally refer to the signal voltage. Signal voltage is only one component of what
determines power (watts). And as mentioned earlier, wattage is not the most accurate
measurement of power.

Amplitude alone does not determine power (or loudness in audio), but it does affect it.
The amplitude of a sound is measured in decibels (dB) of SPL (sound pressure level).
But again, this still does not paint a complete picture of power. Only the sound level at
one point in time and one frequency of the audio spectrum is being measured.
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Amplifiers are devices or circuits that increase the amplitude of the signal fed into them.
Any additional changes in the nature of signal are a form of distortion. The term
distortion is a bit misleading. In playing a guitar, for instance, guitarists use a series of
footpedals (or digital units) to alter the sound of a guitar. One or more of these pedals is
a distortion pedal. Combined with other effects, distortion can sound fuzzy and harsh, or
hollow and clean. For amplifiers, the goal is to output the same signal as the one coming
into the input (the sound source).

Impedance
Most consumer amplifiers are made to conform to standard expectations for input and
output impedances. Most inputs accept impedance matches from 47k to 100k ohms, and
outputs are rated for 4 ohms (most automotive speakers), with high power systems
capable of 1 ohm loads or smaller.

Most home and pro speakers and amps are rated at 8 ohm loads. There are a few units
that have different ratings to accommodate special purpose applications, but we need not
consider those here.

Distortion
Modern designs and devices inside most amplifiers allow distortion levels that at 1
percent or less, are essentially imperceptible by a normal human being when the unit is
played at the prescribed parameters and loads. Thus, Total Harmonic Distortion (THD)
and Intermodulation (IM) distortions have effectively been reduced beyond the threshold
of human perception when played within expected levels. Keep in mind that there are
plenty of other opportunities for distortion to creep into the audio program at many other
points in the chain of reproduction. Microphones, speakers, and their operating
environments are the most common sources of serious distortion.

Power
But, the real trick for most consumers is to figure out how much power is required for the
specific speaker and application involved.

Loudspeakers have a complex inductive reactance associated with the voice coil and a
resistive loading factor that in combination are known as impedance. This impedance
varies considerably with frequency. But the standard procedure is to select a nominal
value for the purpose of computing the power calculation. For car amplifiers, this is
usually four ohms, but with higher power systems this can be much lower. The standard
formula multiplies the voltage by the current, or the voltage squared divided by the
impedance. The product is the amplifier's power potential in watts.

Note that amplifiers, like light bulbs only consume watts when they are actually creating
sound in speakers. For this reason, no matter what the capacity of the amplifier and
woofer, normal room volume will, on average, only need about 5 to 10 watts for sound
thought to be loud. The rest of the extra ten to thousand watts are used only in creating
deep loud bass.
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An amplifier's power is dependent on the voltage applied to it and the current flow it can
sustain without breakdown or overheating in the presence of a normal load. Moreover,
these functions must be performed without incurring any form of perceived distortion.
Fortunately, modern electronics makes it possible to meet these requirements without
great expense. For more on this critical subject, see - Power

Clipping Distortion
However the worst form of amplifier malfunction occurs when users try to make them
perform outside of their capacity. The usual symptom is an item called clipping
distortion. This is present when either the amplitude of the signal being passed is too
large, or the impedance load is too heavy for the rated output capacity. In practical terms,
this is the equivalent of increasing the volume level to the maximum on a very loud
sound, or attaching 10 woofers in parallel on each output terminal. This means that the
most important specification to be observed when choosing an amplifier, is to make
certain that both the usage and the intended load will not cause the amplifier to go beyond
its clipping point.

Peak Power
Because many people prefer to listen to something other than constant-tone sine waves,
program dynamics can vary the load on an amplifier from moment to moment.
Consequently, most amplifiers are tolerant of the occasional demand for peak power that
goes beyond its continuous power rating, and in many cases this tolerance can be
sustained for very small periods (microseconds) of time so as to pass sudden burst
energies without objectionable distortion or stress.


Probably the best practical advice that can be given to the prospective amplifier buyer is
to select speakers appropriate for the usage and space you intend, and then choose an
amplifier that can meet those requirements without stress.

However the majority of amplifiers in today's market will not list all or even most of
these figures.

Distortion Tolerances
The minimum distortion specifications that will permit an amplifier to meet high fidelity
standards are:

Total Harmonic Distortion (THD)
At normative load (4 ohms) the THD should be less than 1 percent. (The lower the
number, the less significance it has. 004% is no better in practical terms, than .1%)

Intermodulation Distortion (IM)
The IM should be less than 2.5 percent (the lower the better, but usually not listed in most
current specifications.)
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Power Bandwidth
The frequencies for which the full rated power output of the unit can be applied: at least
20 to 20,000 hertz, the range of human hearing. More is not necessarily better.

Signal to Noise ratio (SN)
The ratio of inherent noise produced by the internal components of the amplifier to the
average program material: Min 85 dB (although in a car environment which is inherently
noisy, 55dB would be OK. The higher the number, the-slightly-better). Howsever, if you
have perceptible noise associated with the engine operation, check here

Sensitivity Rating
The sensitivity rating should be at least 230Mv @47k ohms for full output.

Power Output Ratings
Use the RMS or continuous power ratings instead of the much higher and much less
reliable so-called peak or MAX output specification. In the absence of an RMS rating, it
can be safely estimated that RMS power is at most 50 percent of the peak power
specification. Remember that to double the loudness in perceived sound, the amplifier
must produce 10 the amount of electrical power in watts. Also, a sound in a car that is
subjectively judged to be really loud can be produced by as little as 10 watts. One twice
as loud would have to use 50 watts, and twice as loud as that, would require 500 watts.
See our section on Power Ratings.

Bridged Power
This is an arrangement of the amplifier circuit where-in the separate built-in stereo
amplifiers are each given one phase of the unified mono input signal, which is then
recombined to yield an output that is usually at least twice as high as the individual stereo
outputs. Or, 50 watts stereo would be converted to 100 watts mono.

Built-In Crossover
There are arrangements on some amplifiers that provide a special switch allowing the
amplifier to respond only to the bass (LPF), or the treble (HPF), or the full spectrum of
the signal. This allows the amp to feed only the appropriate drivers without an external
crossover in the speakers. It also means that either you will depend on the receiver for the
full range source signals, or you'll have to have more than one amplifier.

Bass Boost Circuit
A switched circuit that increases the bass response by anywhere from 8 to 20 dB. Be
careful though, as this can quickly produce clipping distortion in some systems.

Mosfet Output Circuitry
Popular Output devices that produce less heat and greater efficiency in class AB circuits
than older bipolar output transistors. These are now fairly common in most amplifiers.

Power
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Watts appear to be an easily understood figure that conveys a reasonable picture of how
powerful an amplifier is at a glance. Or so it would be if the "kick it up a bit" marketing
boys had not gotten to it. Back in the old days (1982) It was FTC mandated, for the
manufacturer to provide a comprehensive single criteria, power specification. However,
with the de-regulation craze of the 80's, this requirement was dropped in favor of, " that
old marketplace magic." This basically means "caveat emptor" rules. We will do our best
here to give you some basis for judgment, however.

There are a number of terms that apply to descriptions of a unit's power output as stated
in watts.

A watt itself is a unit of energy that can be correctly described as the power used when
energy is expended at the rate of one joule per second. A Joule is a quantity of work or
heat that is generated equivalent to the force of one Newton moving an object at the point
of application, a distance of one meter.

Now this wonderfully concise physical description can be as well applied to the actions
of amplifiers upon their loads (speakers) as it can to any other phenomenon. When
electrical power generated by the amplifier is applied to a load to do work, (move a cone
back and forth) the resulting energy expenditure can be uniformly measured in a standard
way, and applied to all other similar situations.

Where are Watts Found
It is important to remember that amplifiers create an amount of electrical potential that
does not become watts untill the energy is converted to another form. This happens in the
speaker, where the voice coil consumes watts of electrical energy as it converts it to
sound amplitude as measured in decibels.

Multiple power points
Another favorite trick is to just throw out a number for woofers with two voice coils or
amplifiers with 2 or 4 channels. This invariably turns out to be the maximum watts for all
functions. So: "300 MAX watts Four Channel Amplifier" really means 150 watts RMS
divided into four channels or 37.5 watts RMS per channel. Often it can mean less.
Decidedly less impressive, eh? Or, for a woofer, "400 watt dual voice coil woofer" really
means 200 watts RMS divided by two coils or 100 watts RMS per coil. This could yield
disappointing results. Unfortunately, these descriptions are not always consistent. If they
were, it would be easier for consumers to pin them down.

Bridging
But that's not all! There are plenty more complications where these came from. For
instance in amplifiers, there are amps with not only multiple channels, but the capability
of being bridged.

This means that any two ( but only two) channels can be bridged to form an amplifier of
approximately double the capacity of a single channel. It does this by taking a mono input
signal and dividing it between the positive peaks of the signal and the negative valleys,
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and amplifying each separately. These separated polarities are then reunited at the
amplifier terminals to form a unified signal again for the woofer.

Thus, two 75 watt RMS amplifiers can become a single 150 watt RMS amp. In a four
channel bridgeable amplifier, four can be come two, each with twice the power of a
single channel.

But look out here! Most amplifiers are of the class AB variety. this means they can be
bridged to a 4 ohm load only, yet some brands advertise the total of the 2 ohm load each
channel can carry separately. This is very misleading and should not be confused with the
amplifiers described in the next paragraph.

Multiple power ratings
Increasing numbers of amplifiers, particularly monoblock, high current or digital models,
have the capacity to handle low impedance loads, sometimes all the way down to one
ohm. As the impedance figure goes down, the wattage figure goes up. This reflects the
fact that efficiency increases as the load becomes heavier (ohms figure gets smaller)
Consequently, the greatest efficiency can be realized with amplifiers capable of
delivering stable operation into very low impedance woofer circuits.

While 4 ohm remains the industry standard for car amps and woofers, capacities are
tending downward, mostly because of the increase in the watt numbers attendant to lower
impedance carrying ability. At a minimum, better quality units will list "2 ohm Stable" as
a feature. Since most speaker loads are highly variable in operation, and will have
occasions when operational impedance of a 4 ohm system can go below 2 ohms, it is
good to have this capacity so that distortion is reduced at high amplitudes, especially.

Dual voice coil woofers can have coils that are 1, 2, 3, 4, 6, and 8 ohms. This means that
such woofers can be configured to operate either singly or separately at the most efficient
level.

These woofers can be connected in a variety of ways to the multiple impedance
amplifiers. Dual voice coils can be connected either in parallel or serial circuits. A woofer
with two 4-ohm coils connected serially would produce an 8-ohm total, or in parallel
(with both + terminals and both - terminals tied to one set of amplifier terminals) a 2-ohm
load. Of course, a single voice coil can be used also, albeit at half the rated power.

Check Impedance Calculator

With two woofers connected in a serial circuit, two 2-ohm woofers can present a 4 ohm
load, or two 1 ohm woofers can present a 2 ohm load. The best common configuration is
to use two dual voice coil woofers with 4 ohm coils. All in parallel, this will make a
highly efficient 1 ohm load, with power handling equal to the total RMS of both woofers.

But in all cases, the idea is to match both the impedance and the output power capacity of
both the amp and woofer units. A good relationship is for the Amplifier to supply
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between 10 to 30 percent more power to the woofer than the woofer's nominal RMS watt
handling rating. Thus, a 200 watt woofer should optimally have a 225 to 260 watt
amplifier channel connected to it.

But remember that all watt indications above are …. (what kind?) ….RMS, that's right.

Unfortunately, there are other ways in which watt measurements are taken that lend
themselves to the kind of exaggeration and hyperbole that creates so much confusion for
shoppers and owners of such equipment. Let us examine a few ways in which test
conditions make it possible for manufacturers to make doubtful claims:

The power supply
All amplifiers will be able to supply larger waveforms when higher than usual voltages
are applied to them. An amplifier that produces 200 watts at a normal 12 volts may
produce up to 300 watts when the power is boosted to 15 volts. Of course such an
arrangement does not obtain in too many cars, and it is stressful on the amplifier, but that
does not stop some sellers from using it.

Number of operating channels
When power is measured on a channel with only that channel operating, the resulting
watts will be substantially higher than if all channels are operating and loading the unit's
power supply uniformly - the condition in which most people operate their system.

Unspecified load factors
Some makers will use lower resistance than customary for obtaining power
measurements, that is, a very low resistor value from half an ohm to 2 ohms and this is
presented as the un-attributed, presumably standard impedance value. The value for the
advertising cheat of not saying anything, is that the reader tends to presume everything.

Biased testing factors
Differences in ambient temperature, the amount of total harmonic distortion (THD)
produced, and tested frequency bandwidth can also impact the number of RMS watts that
can be produced. For instance an amplifier operated to extreme capability will produce
500 watts RMS, but only with 18 percent distortion. While people are more tolerant of
high distortion than is generally realized, this amount would be painfully unacceptable to
most.

Car Amplifiers Frequently Asked Questions


Power
How much power do I need to get optimum performance from my car's sound system?
What's the biggest amp I can hook up to my car's electrical system?
Where should I ground my amp?
What is a "high-current" amplifier?
How much power do I need for my subwoofers?
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Speakers
What should I know about my speakers' impedance?
How can I drive a pair of speakers and a subwoofer with a single car audio amplifier?
My new car amplifier is "2-ohm stable." How can I take advantage of that?

General
What's the story on the different amplifier "classes"?
What's the difference between "parallel" and "series" wiring?
When should I use a mono amplifier instead of a multichannel amplifier?
What are the benefits of hooking up 2 subwoofers to a mono amplifier? How would I
wire them?
Can I bridge my mono amplifier?
I'd like to add a power amplifier to my factory-installed car radio. What are my options?
How do I fine-tune my amplifier's gain and bass boost settings?

Q: How much power do I need to get optimum performance from my car's sound system?

A: Since every car stereo is different, there's no magic "wattage formula." As long as you
stay within the recommended power range of your speakers, increasing power will
always add richness and depth to your music. Compare a spinet piano to a concert grand.
The small piano is good enough to play music clearly, but move up to a grand and you'll
gain better tone, greater harmonic detail, and more volume. The larger instrument is
simply more powerful.

Here are a couple things to consider, though:

How efficient are your speakers? Your speakers themselves have a direct influence on the
overall “power" of your system. If you're planning on powering your speakers with your
in-dash receiver, efficient speakers (sensitivity of 90 dB or higher) will give you more
bang for the buck.

Installing high-performance component speakers? An outboard amp will generate
maximum performance.

Are you adding a subwoofer? Subs need substantial amounts of power to reproduce the
lowest tones, so it's essential to use an outboard amplifier with them. You should count
on using more power for bass than you use to power all your full-range speakers. If your
receiver puts out 20 watts RMS x 4 channels (80 watts total), send at least 80 watts to
your sub. Using a 50 watt x 4 amp to drive your components? Dedicate at least 200 watts
for bass.

How good is your wiring? Your system's chain of components is only as strong as its
weakest link, so don't cheat your amps and speakers with substandard power cable and
speaker wire.
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Before you buy, consider your car. If you drive a quiet car with the windows up, you'll
need much less power than someone who offroads in a Wrangler. Speaker location,
extraneous road/car noise, noise damping material, and personal taste are factors that may
affect how much power you'll need in your ride.

Q: What's the biggest amp I can hook up to my car's electrical system?

A: Your car's alternator ampere rating determines how powerful an amplifier you can
install. Multiply the ampere rating by 40% and you'll get a rough idea of how much
reserve current capacity your car's system has. Next, you'll need to calculate the
approximate current draw of the amplifier you're considering installing.

To calculate the current draw of an amplifier, multiply the number of channels by the
RMS watts per channel (a 2 channel amp rated at 300 watts RMS per channel would be
600 watts). Double it to account for amplifier inefficiency (600 watts X 2 = 1200 watts),
then divide by the average output Voltage of an alternator, 13.8 volts (1200 divided by
13.8 = 87 amps). Since the average music signal requires about 1/3rd of the average
power in a test tone, divide by 3 (87 amps divided by 3 = 29 amps). The result is the
amplifier's approximate average current draw.

A fast-and-nasty way to ballpark an amplifier's current draw is to divide the total fuse
value of the amp by two. For amplifiers with multiple fuses, the rating of all fuses
provided with the amp must be added together. This will likely produce a significantly
higher estimate than using the proper formula. Although inaccurate, this will err on the
side of safety.

Finally, compare the amplifier's approximate current draw to your vehicle's reserve
current capacity to determine if the electrical system can support the amplifier.

If all those numbers are a bit much, here's a simpler way to think about it: an alternator
capable of producing 65 amperes is usually adequate for systems up to 270 X 2 watts
RMS. A compact car with a 35-amp alternator can accommodate around 150 X 2 watts of
power, while a Sport Utility with a 145-amp alternator can handle a 600 X 2 watt system.
A capacitor can help if your system is drawing a little too much power. Car audio
competitors often replace their vehicle’s alternators with heavy-duty upgrades to
accommodate big power demands.

Q: What is a "high-current" amplifier?

A: A "high-current" amplifier is a high-performance amp capable of passing high current
into very low impedances without overheating or shutting down. In a perfect world with a
perfect amplifier, power output would double every time the impedance was halved. For
example, an amplifier rated at 50 watts RMS x 2 channels into 4 ohms would produce
100 watts by 2 into 2 ohms. Unfortunately, this is not a perfect world, and most
amplifiers can't do that.
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The best way to identify a high-current amplifier is to look at what happens to the power
rating as the impedance drops. The closer it comes to achieving the perfect world
scenario above, the more current it is capable of passing.

Q: How much power do I need for my subwoofers?

A: That depends on what sort of bass impact you hope to achieve. If you just want to hear
a bit more bass than your regular stereo speakers can put out, you can get what you need
with an efficient 6-1/2" subwoofer driven by as little as 30 watts RMS. But when you're
looking for really big bass, you'll need at least a 10" or 12" subwoofer and a minimum of
150 to 200 watts to drive it. Low bass notes are power hungry, and the more wattage you
feed them, the better they sound. In general, the larger your subwoofer and the harder you
want it to hit, the more power you’ll need.

Remember, if you're driving one sub, you can "bridge" a 2-channel amp to get a
significant increase in output.

individual product descriptions list bridged output for each of our amplifiers.

selection of Mono Subwoofer Amps, since their features and design are specifically
tailored for the job of driving low frequencies.

recommend that you drive your speakers/subwoofers with at least 70% (70-100%) of
their maximum RMS (not peak) rating to get them to perform at their optimum. The
closer to 100% you power them, the harder they hit and the better they sound.

Q: What should I know about my speakers' impedance?

A: Impedance is the load value that your speakers present to your power source — the
amount of resistance they provide to the current flowing from your amplifier. While it's
convenient to refer to a speaker's impedance as being a fixed value (say, 4 ohms) over a
speaker's entire frequency range, the impedance typically varies with the frequency of the
input signal. So when we say a speaker is a 4-ohm speaker, think of this rating as a useful
approximation.

The key things to know about impedance are your speakers' ratings, your amplifier's
ratings, and whether they match. That's enough to keep you out of trouble, and even let
you get a little creative when you're designing your system.

In the car audio world, the typical stereo amplifier is stable down to 2 ohms in stereo, or 4
ohms in mono (or "bridged") operation. Most car audio speakers are rated at 4 ohms, but
2-ohm, 8-ohm, and dual voice coil subwoofers are increasingly common. Car audiophiles
know that they can actually make their systems hit harder by combining higher-
impedance woofers.
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Bridging a stereo amplifier down to a single channel is a great way to maximize power to
a single speaker. You could use this single channel to drive a single 4-ohm woofer. But
some fans of aggressive bass prefer to hook up two parallel-wired 8-ohm woofers — the
subwoofers' total impedance remains the same but the overall surface area is increased,
raising the system's sound pressure level. If you've invested in an amplifier that's stable
down to 2-ohm mono (1-ohm stereo), you can further raise the stakes in this game by
introducing up to four parallel-wired woofers to your bridged amp. You'll get more bass
from the increased surface area and more power output as well.

But before you rush out to run your car audio amplifier at the minimum impedance it can
handle, bear in mind that there are trade-offs involved. As you decrease the impedance
your amplifier sees, the amplifier's distortion spec will rise. On the other hand, some
people claim that, in the hard-thumping arena of car audio subwoofers, such changes are
inaudible and insignificant.

So what's the bottom line? Make sure you know your speakers' impedance ratings, as
well as the minimum impedance of your amplifier in bridged and stereo modes. Then
experiment carefully and go with what sounds right.

Q: How can I drive a pair of speakers and a subwoofer with a single car audio amplifier?

A: One of the keys to getting the most out of your audio investment is choosing gear that
will go to work for you now, and won't become obsolete as your system grows. Most car
audio amplifiers boast a design flexible enough to keep them in the game as your set-up
expands.

If you go with a 4-channel amplifier, powering a pair of front speakers and a subwoofer
is a breeze. You'll simply want to run your amp in what we call "true" 3-channel mode.
To do this, bridge the rear channels to power your subwoofer, while the front channels
drive the pair of regular stereo speakers. Bridging the rear channels means combining
them in mono mode to create a single channel. Choose an amp that lets you engage a
built-in, low-pass filter on this bridged channel. The crossover, along with the increased
output from the mono channel, makes this an ideal way to power your sub.

As your system grows, you may dedicate a separate amplifier to your sub. At that time,
you could add another pair of stereo speakers for rear fill, and run your 4-channel amp in
stereo mode.

But what if you're starting out with just a simple two-channel amp and you still want to
power a pair of stereo speakers and a sub? No problem. That's where a feature known as
"Tri-way mode" (or “Tri-Mode") kicks in.

Amplifiers described as "Tri-way capable" means you can attach a Tri-way crossover to a
pair of stereo amplifier channels to produce three channels — two stereo channels for
front speakers, and one mixed-mono channel for your sub.
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The Tri-way crossover is actually a special kind of passive crossover network. It applies a
high-pass filter (typically at around 100 Hz) to each of your amplifier's stereo channels,
sending the information above the crossover point straight to your stereo speakers. It also
combines the low-frequency information from each of these channels into a single, mixed
mono channel, which is sent to your sub. As is the case when you bridge an amplifier, the
mono channel delivers more output than the stereo pair.

If you're about to purchase an amplifier, you'll get the most value by purchasing one that
can run in true 3-channel mode. If your goal is to eventually own a high-performance
"audiophile" car audio system, you'll want the performance and features that these amps
typically provide. You’ll be able to adjust the volume of the sub, and in most cases, the
frequency of a built-in electronic crossover, as well. You give up these conveniences
when you go Tri-way.

But while Tri-way mode doesn't give you the degree of control or performance that a true
3-channel system provides, it is an affordable, effective way to get the most out of a
budget system built around a single amp. And because Tri-way crossovers are relatively
inexpensive, if you decide to add more amplifiers and reconfigure your system later on,
you won't be out a huge investment.

Q: My new car amplifier is "2-ohm stable." How can I take advantage of that?

A: Typically, a car stereo amp "sees" a 4-ohm impedance. When we say an amplifier is
stable down to 2 ohms, we're usually referring to the minimum impedance it can handle
in stereo (2-channel) mode, not bridged (mono) mode. The lower the impedance
(resistance or "load") an amplifier sees, the more power it produces, and the louder your
music plays.

A common way to get a 2-ohm stable amp to produce the extra power it delivers at lower
impedance is to wire your speakers in parallel. While series wiring always raises your
impedance, parallel wiring always lowers it. See below for instructions on parallel
wiring. For example, you can dramatically increase your system's impact by hooking up
not one but two subwoofers in parallel to each of your amp's channels. Or, if you're
looking to max out your 2-ohm stable amp's muscle with only a single pair of hard-hitting
drivers, consider our dual 4-ohm voice coil subwoofers.

Q: What's the story on the different amplifier "classes"?

A: An amplifier's circuit design determines its class of operation. Class A amplifiers are
desirable for the high quality of their sound, but the design is not particularly suited to car
applications because of inefficiency and high heat production. Car amplifiers that boast
Class A design are usually Class A/Class AB hybrids. The Class AB design is most
commonly used for car amplifiers because it combines reasonable efficiency, low
distortion, and reliability.
                                                                                         14


Class D amplifiers ("D" does not stand for "digital") boast higher efficiency, produce less
heat, and draw less current than traditional Class AB designs, but they tend to have more
distortion. Since low-frequency distortion is almost impossible to detect, compact Class
D amps rule the bass kingdom. Class T amplifiers combine characteristics of
conventional Class AB and cutting-edge Class D designs for great power, compact size,
and minimal production of heat.

Q: When should I use a mono amplifier instead of a multichannel amplifier?

A: Because mono amps tend to be Class D amplifiers, they are a good choice for
powering subwoofers — Class D amplifiers have a high power-to-heat ratio and
excellent efficiency, which are exactly what you want when dealing with power-hungry
low frequency signals.

Most mono amplifiers are designed to run at 2 ohms; some are even 1-ohm stable.
Multichannel amplifiers, on the other hand, are typically designed to work with a 4-ohm
load. This is an important difference when using your amp to power multiple subwoofers,
because you won't be able to bridge your multichannel, 4-ohm stable amp to power
multiple subs that present less than a 4-ohm load. Instead, use a mono amplifier to power
a 2-ohm load — two 4-ohm subwoofers, or 2, 2-ohm dual voice coil subwoofers, for
example. You'll be able to push your subwoofers with the mono amp's maximum power,
without running at dangerous impedance.

Q: What are the benefits of hooking up 2 subwoofers to a mono amplifier? How would I
wire them?

A: The benefits of hooking up two subs to a mono amplifier are the same as hooking up
any other number of subs to a mono amp: you can push the subs with more power at
lower impedances. Because lower frequencies are less directional (i.e. it's more difficult
for your ears to determine where low frequencies come from than highs), bass is often
transmitted in mono. Mono here refers to a single channel (as opposed to stereo, or two
channels), not one speaker.

Most mono amps have two sets of speaker terminals for convenience of installation: if
you are hooking up two subs to the amp and using large-gauge wire, it gives you a place
to attach the wires without having to trim them, appearing as if each subwoofer gets its
own terminal. But in reality, these terminals are actually tied together inside the amp —
both positives are going to the same place inside the amp, as are both negatives. If you
are using more than two subs, then you simply use parallel or series wiring (or a
combination) to get as close to the minimum impedance of the amp as possible

(See Crutchfield subwoofer wiring diagrams for more information).

Q: Can I bridge my mono amplifier?
                                                                                           15


A: No, you can not bridge a mono amp because there is nothing to "bridge" to —
whatever impedance load you present to amplifier is the actual load that it sees. This
differs from a multichannel amp in that when you bridge two channels together, you
halve the load presented to them (for example, 2 4-ohm woofers wired in parallel and
bridged to a stereo amplifier is "seen" as a 1-ohm load to that amp).

Q: I'd like to add a power amplifier to my factory-installed car radio. What are my
options?

A: Because it's a great way to increase musical detail, dynamic range, and volume,
adding a power amplifier is an extremely popular factory system upgrade. And when the
weather gets warm, even more people tell us they're looking for a system that can deliver
roll-down-the-windows volume.

But your factory radio poses a challenge. It usually doesn't offer preamp outputs. So how
will you hook up to the preamp level inputs found on the typical aftermarket amplifier?
The easiest way around this roadblock is to choose an amplifier with speaker-level inputs.

Speaker-level inputs let you use your factory speaker wire to feed an amplifier the
musical signal from your radio. You won't need an RCA patch cable or a receiver with
preamp outputs. But if the amplifier that really appeals to you doesn't have speaker-level
inputs, don't sweat it. You can use an RCA patch cord with an inexpensive line output
converter and still get signal from your factory speaker wire.

In addition to connections for power and ground, any speaker-level amp hook-up requires
you to tap into the factory speaker wire. Make the connection with aftermarket speaker
wire you run to your amp (or line-level adaptor). In most vehicles, the easiest place to
access the factory speaker wire is from the trunk, where it connects to rear speakers
below the deck.

If your vehicle doesn't have a trunk, you'll want to connect to the factory speaker wire
behind your radio. When you get your gear from Crutchfield, you'll have access to our
exclusive toll-free Technical Support. Our experts will help you identify the correct
wires.

When you're ready to actually connect the new speaker wire to the factory speaker wire,
strip back the insulation on the factory cable, without cutting the actual wire. (A quality
wire stripper makes this type of careful cutting easy.) Then, wrap the stripped-back
aftermarket speaker wire around the exposed factory strands. Solder for the best possible
connection, and then cover with electrical tape.

Well there you have it — the "nitty as well as the gritty". Remember, this is a relatively
simple installation, and definitely one of the best ways to fill your car with truly dynamic
sound.

Q: How do I fine-tune my amplifier's gain and bass boost settings?
                                                                                            16



A: Setting the "gain" or input sensitivity control is an important adjustment common to
all amplifier installations. Proper gain setting helps reduce noise and distortion and
allows for the widest possible dynamic range. Here's how to do it:

Turn your amplifier's input level controls all the way down.

Put in a tape or CD or tune in a radio station. Turn up your receiver's volume control.
You’ll begin to hear music at faint levels. (Audiophiles and sound competitors may want
to use a dedicated test disc. When you start hearing distortion, lower your receiver's
volume control until the distortion disappears. At this point, you have as much signal as
possible passing from your receiver into your amp. (This gives you maximum signal-to-
noise ratio, so you'll enjoy clean sound and your system will be less prone to engine noise
problems). Now begin adjusting your amp's input gain.

Turn the input level controls up until the system is as loud as you can stand it or until you
begin hearing distortion — whichever comes first. If you hear distortion, decrease the
gain settings slightly. By following this procedure, you'll optimize your amp's
performance at the receiver's maximum volume level, so you can crank your system
almost all the way up without amplifying any distortion, or damaging your speakers.
Keep in mind that this adjustment does not affect the power output of the amp — you're
simply setting the amount of input signal needed for optimum sound quality from your
system.

Car stereo competitors sometimes employ a technique called "gain overlap" to wring
some more dBs out of their rigs while keeping distortion out of the audible range. Many
amplifiers have a bass boost function. In most cases, it is a variable control — you simply
dial in the amount of boost you’d like to hear. Bass boost levels can range from +6dB to
+18dB, depending on the amplifier.

As you experiment with this adjustment, you'll notice that the boost is centered at a given
frequency, so you'll still experience some bass boosting at frequencies above and below
that point. Make sure that your system is turned off or operating at low volumes when
you engage or turn up your bass boost control — boosting bass at high volumes can
damage your speakers.

Car Power Supply
If you think that all you need is a big amplifier and huge speakers for a true high power
audio system, you may have overlooked something. Adding high power car audio
components to your vehicle without an adequate power supply system may lead to
disappointment, frustration, distortion and damaged equipment.

Let's say you install a 1000 watt RMS amplifier in your car. The vehicle's charging
system must produce sufficient current to run the amplifier. How do you determine how
much current is needed?
                                                                                          17


Simple: divide the RMS power rating of the amplifier by the amount of voltage your cars
electrical system will produce.

Most vehicle electrical systems will produce approximately 13.8vdc with the engine
running. Thus, 1000 watts RMS (doubled to allow for the max, in this formula) divided
by 13.8 volts, draws around 145 amperes of current. The electrical system of the vehicle
will need to produce an extra 145 amperes of electrical current above the basic
requirement of the car, to operate your amplifier and it's woofer at a high performance
level.

One of the biggest mistakes made by consumers and even a few installers, is failing to
ensure enough additional energy resources to handle the extra load of the audio system.
But first you must understand how the electrical system operates. Here's a brief summery.

Engaging the starter begins the process of initiating the system. The battery stores enough
kinetic power to operate the starter. Once the engine is running, the electrical burden is
shifted to the alternator. The alternator uses the engine's mechanical power to produce
electrical (AC) current. The AC current is rectified - changed to DC (direct) current,
which is what operates, all the electrical devices in the vehicle. The alternator also
provides enough residual energy to recharge the battery.

Everything works well so long as the total power requirements of the vehicle do not
exceed the capacity of the alternator's output. If the output is overloaded by an excessive
draw, then power will be drained from the battery. If the alternator and battery combined
cannot meet the demand, then the vehicles electrical devices may begin to fail. As voltage
drops, current (amperage) draw increases, and that increases heat in wiring and
components. This is the reason that loud bass will sometimes damage components if the
power supply system is inadequate.

A first consideration to determine if the charging system is adequate is the alternator
itself. If possible, look for the maximum output, or HOT RATING on the alternator. If
this information is not available on the car, call a local parts store or car dealership and
ask them to look up the stock alternator for your vehicle. The hot rating indicates the
amount of power the alternator will produce once the engine reaches it's normal operating
temperature. With this information, you can determine if the charging system has
sufficient capacity to accommodate your power audio system. If your components will
draw more than 20 amps over the hot rating of the alternator, you may want to consider a
high output alternator. If only a little extra current (12 to 19 amperes) is needed, the
easiest way to enhance the system is to add an extra battery, or replace the existing
battery with a larger one. If the difference is less than 5 amps, the existing power system
will be able to handle it. For this, a capacitor is the best solution for every system,
regardless of the presence of an adequate, but slow acting power supply.

The load imposed by audio signals is usually not constant, but will vary with the greatest
draw occurring in peaks of a relatively short interval. It is for this reason that the fuses
                                                                                         18


recomended for most amplifiers are rated at slightly less than the max theoretical current.
Keep in mind that it is desirable for the fuse to blow before the amplifier does.

strongly recommend that if you anticipate making any changes to your car's electrical
system that you engage the services of a professional. Keep in mind that any increase in
generating capacity/load will usually diminish to a small degree, the cars available
horsepower.
                                                                                            19



Chapter --: F/X Processors
   DSP
   Equalizers (Stand-alone units, Built-in, Digital, Parametric)
   Crossovers
   Active and Passive crossovers
   Crossover Components
   Orders of crossovers
   Crossover Values
   Crossover Points
   Crossovers for Three-Way Speaker Systems
   Mixing and matching different crossover orders
   Resistance
   L Pads
   Compressor/Limiter
   Bass Boost
   Reverb units


What is DSP: Digital Signal Processing?
DSP, or Digital Signal Processing, as the term suggests, is the processing of signals by
digital means. A signal in this context can mean a number of different things. Historically
the origins of signal processing are in electrical engineering, and a signal here means an
electrical signal carried by a wire or telephone line, or perhaps by a radio wave. More
generally, however, a signal is a stream of information representing anything from stock
prices to data from a remote-sensing satellite. The term "digital" comes from "digit",
meaning a number (you count with your fingers - your digits), so "digital" literally means
numerical; the French word for digital is numerique. A digital signal consists of a stream
of numbers, usually (but not necessarily) in binary form. The processing of a digital
signal is done by performing numerical calculations.

Analog and digital signals
In many cases, the signal of interest is initially in the form of an analog electrical voltage
or current, produced for example by a microphone or some other type of transducer. In
some situations, such as the output from the readout system of a CD (compact disc)
player, the data is already in digital form. An analog signal must be converted into digital
form before DSP techniques can be applied. An analog electrical voltage signal, for
example, can be digitised using an electronic circuit called an analog-to-digital converter
or ADC. This generates a digital output as a stream of binary numbers whose values
represent the electrical voltage input to the device at each sampling instant.

Signal processing
Signals commonly need to be processed in a variety of ways. For example, the output
signal from a transducer may well be contaminated with unwanted electrical "noise". The
electrodes attached to a patient's chest when an ECG is taken measure tiny electrical
voltage changes due to the activity of the heart and other muscles. The signal is often
                                                                                         20


strongly affected by "mains pickup" due to electrical interference from the mains supply.
Processing the signal using a filter circuit can remove or at least reduce the unwanted part
of the signal. Increasingly nowadays, the filtering of signals to improve signal quality or
to extract important information is done by DSP techniques rather than by analog
electronics.

Development of DSP
The development of digital signal processing dates from the 1960's with the use of
mainframe digital computers for number-crunching applications such as the Fast Fourier
Transform (FFT), which allows the frequency spectrum of a signal to be computed
rapidly. These techniques were not widely used at that time, because suitable computing
equipment was generally available only in universities and other scientific research
institutions.

Digital Signal Processors (DSPs)
The introduction of the microprocessor in the late 1970's and early 1980's made it
possible for DSP techniques to be used in a much wider range of applications. However,
general-purpose microprocessors such as the Intel x86 family are not ideally suited to the
numerically-intensive requirements of DSP, and during the 1980's the increasing
importance of DSP led several major electronics manufacturers (such as Texas
Instruments, Analog Devices and Motorola) to develop Digital Signal Processor chips -
specialised microprocessors with architectures designed specifically for the types of
operations required in digital signal processing. (Note that the acronym DSP can
variously mean Digital Signal Processing, the term used for a wide range of techniques
for processing signals digitally, or Digital Signal Processor, a specialised type of
microprocessor chip). Like a general-purpose microprocessor, a DSP is a programmable
device, with its own native instruction code. DSP chips are capable of carrying out
millions of floating point operations per second, and like their better-known general-
purpose cousins, faster and more powerful versions are continually being introduced.
DSPs can also be embedded within complex "system-on-chip" devices, often containing
both analog and digital circuitry.

Applications of DSP
DSP technology is nowadays commonplace in such devices as mobile phones,
multimedia computers, video recorders, CD players, hard disc drive controllers and
modems, and will soon replace analog circuitry in TV sets and telephones. An important
application of DSP is in signal compression and decompression. Signal compression is
used in digital cellular phones to allow a greater number of calls to be handled
simultaneously within each local "cell". DSP signal compression technology allows
people not only to talk to one another but also to see one another on their computer
screens, using small video cameras mounted on the computer monitors, with only a
conventional telephone line linking them together. In audio CD systems, DSP technology
is used to perform complex error detection and correction on the raw data as it is read
from the CD.
                                                                                           21


Although some of the mathematical theory underlying DSP techniques, such as Fourier
and Hilbert Transforms, digital filter design and signal compression, can be fairly
complex, the numerical operations required actually to implement these techniques are
very simple, consisting mainly of operations that could be done on a cheap four-function
calculator. The architecture of a DSP chip is designed to carry out such operations
incredibly fast, processing hundreds of millions of samples every second, to provide real-
time performance: that is, the ability to process a signal "live" as it is sampled and then
output the processed signal, for example to a loudspeaker or video display. All of the
practical examples of DSP applications mentioned earlier, such as hard disc drives and
mobile phones, demand real-time operation.

The major electronics manufacturers have invested heavily in DSP technology. Because
they now find application in mass-market products, DSP chips account for a substantial
proportion of the world market for electronic devices. Sales amount to billions of dollars
annually, and seem likely to continue to increase rapidly.

Car Audio Signal Processors
The function of equalizers, crossovers, and other signal processors is to electronically
change the music signal in some way to make it more usable. These processors are
sometimes built into other units such as amplifiers. However, they are at their absolute
best when designed as an outboard unit.

Car Audio Equalizer
The equalizer is a sophisticated tone control for the system, adjusting many different low,
mid and high frequencies. Equalizers come in many forms including dash and trunk
mount units with either graphic, parametric, or quasi-parametric processing. The most
common type of unit is the graphic, in-dash variety. Usually half the height (half-DIN) of
a source unit, this type is the most easily adjustable and therefore the most often misused.
An equalizer should really only be set once to overcome the acoustic problems of the car
and then adjusted only periodically when tuning the system. This is why thirty band trunk
mount units are used in car audio competition more often than the in-dash ten band
variety. When using an equalizer do not overdue the boost on a frequency. If possible try
to cut a frequency rather than boosting another. Over equalizing a system can cause
damage to the components, especially the speakers.

Car Audio Crossover
The crossover's purpose is to divide the music signal by frequency and send these
frequencies to components "downstream" of the crossover. For example, in a system with
a two-way component set and a subwoofer the crossover would send the low frequencies
to the subwoofer's amplifier and the high frequencies to the component speaker
amplifier(s). Crossovers vary in their flexibility. Some only have a few frequencies to
choose from while others have a whole range of frequencies to choose from. The rate at
which the frequencies are attenuated, or cut, can be adjusted on some units.
                                                                                            22



Surround Sound Processors
There are other signal processors that perform various tasks. Some extract information to
be sent to a center channel speaker, some add various sound effects or echoes to the
music while some can even change phasing and delay. Many new units are becoming
available that decode surround sound information on DVD and the new audio disc
formats. These units can be useful (and expensive) but the can also be frivolous (and
expensive). There are very few low quality signal processors that perform these extra
features. They are usually reserved for competition vehicles or for the owner that has
everything.

Features and terms relating to the various processors are as follows:

Bands: This is the number of frequencies an equalizer can adjust at one time.

Center Channel Output: An output that contains the musical information found in both
the right and left channels.

Continuously Variable: This is a crossover's ability to be adjusted to a range of
frequencies rather than a set of a few frequencies.

Curve (Equalizer): This is the way that the equalizer is set from frequency to frequency.

Decibel (dB): This is the measure of how loud a sound is based on a scale of zero
decibels being the threshold of human hearing. Doubling the amplifier power gives an
increase of three decibels while ten decibels is needed for a sound to be perceived as a
sound twice as loud.

Delay: The amount of time, usually in milliseconds (ms), that a signal processing unit
adds to a channel of music. This is usually used to delay the rear channels with respect to
the front channels to give a sense of greater space.

DSP: Standing for digital signal processing it is most commonly found in processing
units to recreate or simulate a specific acoustic environment such as a concert hall or a
disco club.

Graphic: This equalizer has only a set of fixed frequencies that can be adjusted. Most
often found on in-dash units.

Octave: Refers to the distance between two frequencies. One octave is twice the reference
frequency. For example, 200 Hz is one octave away from 100 Hz and 400 Hz is one
octave away from 200 Hz and two octaves away from 100 Hz.

Parametric: This type of equalizer has the ability to have the frequencies of adjustment be
varied as opposed to a graphic equalizer with fixed frequencies.
                                                                                          23


Phasing: Refers to how far a signal varies, in degrees, from another signal. For example,
if two subwoofers are wired with their terminals (+ and -) reversed with respect to one
another they are one hundred and eighty degrees out of phase. This means that while one
speaker is moving out the other will be moving in. Phase can also be changed by
changing the distance two speakers are from the listener(s).

Presets: Some equalizers can be programmed to have more than one equalizer curve to
adapt to different music and driving conditions.

Q: This is the degree that a range of frequencies will be affected by an equalizer. A high
Q will have a narrow range of frequencies that will be affected while a low Q will affect a
broader range.

Quasi-Parametric: This is a parametric equalizer that may also have the Q of the bands
adjusted as well.

Real Time Analyzer (RTA): Sometimes called a "stick", this is a sophisticated tool for
measuring the frequency response of a system over the entire audible spectrum. A type of
sound which is equal at all frequencies, called "pink noise", is usually used in conjunction
with these meters.

Slope: This is the rate at which a crossover attenuates a signal in decibels per octave. For
example, a low pass, 12 dB per octave slope, at a frequency of 100 Hz, will be twelve dB
less at 200 Hz, 24 dB less at 400 Hz and so on. Most active crossovers have an adequate
slope of 12 dB per octave while higher numbers such as 24 dB per octave will give a
better cutoff, especially useful for subwoofers.

Spectrum Analyzer: A display of bouncing lights on the face of an in-dash equalizer that
correspond to the equalizer frequencies that can be adjusted. While eye catching on a
sales floor these can become annoying (and dangerous) when driving.

Equalizers/Crossovers
How to Choose an Equalizer

What to look for:
Besides giving you tight tonal control over your music playback, the equalizers available
from Crutchfield also offer you plenty of other useful features.

Each of our EQs offers a front-to-rear fader for dual-amp balancing, even with a receiver
that has only one pair of preamp outputs. The fader is also ideal for dialing in just the
right amount of rear-fill.

Get Everything You Need
You'll need patch cables to connect an EQ.
Some units have a "listening position" switch to let you adjust the stereo image from left
to right to compensate for "side-biased" listening.
                                                                                           24



You'll also find a "subwoofer output" set of preamp outputs (with a low-pass filter) on
many of our EQs. Some models even engage high-pass filters on the front and rear
channels whenever the subwoofer output is in use. These crossovers allow only certain
frequencies to pass through them (high for your smaller speakers, low for your
subwoofers), keeping your speakers and subs from having to try to reproduce sounds they
weren't designed to. That's like having a free electronic crossover packaged with your
equalizer — a pretty sweet deal.

Parametric EQs have equalization bands with adjustable center frequencies. These
parametric (variable) bands really let you make exact adjustments within a given
frequency range. They give you the maximum tweaking ability.

Some digital EQs let you program your own EQ curves and store them for repeated use.
You can create one curve for rock, another for rap, a third for jazz. After all, each of these
musical forms naturally emphasize different tones.

How an Equalizer Helps Your System
A graphic equalizer gives you ultra-precise tone control. A quality EQ, properly used, can
fine-tune even a high-end system. It makes the difference by catering to your listening
preferences and allowing you to restore great sound that gets disrupted by your noisiest,
most hard-to-handle component — your car.

Vehicle noise, road noise, size and shape of the interior, the reflectivity of glass, and the
absorbent nature of seats all affect your system's sound. You can use an equalizer to
remedy each one of these ills, boosting the frequencies you're missing and attenuating the
ones your vehicle exaggerates.

When you make these adjustments, use a light touch on those slider switches — a boost
of 10 dB works your amplifier ten times harder, and this can introduce distortion. Here's a
tip: Try attenuating frequencies first. For example, before you boost your bass, lower the
midrange and high frequencies a little bit.

Of course, an EQ is also a great way to protect your equipment. For example, if your
system's bass is provided by a pair of 6-1/2" woofers, use an EQ to cut back all
frequencies below 50 Hz. Your amp will work more efficiently and you'll get higher,
cleaner volume while protecting your speaker drivers from tones they can't handle.

The best way to find out what an equalizer can do for your system is to try one out for
yourself. A little hands-on experience and some trial and error tweaking will help you
learn more about shaping up the sound in your car and really bring out the best from your
system.
                                                                                            25


Crossovers Frequently Asked Questions

What is a crossover and do I need one?

What's the difference between passive and active crossovers?

How hard is it to install a crossover?

What does the phase switch on an electronic crossover do?


Q: What is a crossover and do I need one?

A: For the most complete answer to this question, you'll want to check out our crossover
article. In simple terms, a crossover is like a traffic cop for audio frequencies. It filters
and directs frequencies to allow only a certain range of frequencies to reach a certain
speaker. Frequencies outside that range are attenuated or blocked.

Every system needs a crossover of some type. How sophisticated a crossover you need
depends on how elaborate a system you're planning. If you're running just a basic system
with an in-dash receiver and four speakers, then you don't need to worry about buying a
crossover. Your full-range speakers already have passive crossover networks built in
between the woofers and tweeters. And if you're just driving full-range speakers with an
external amp, the crossover network on the speakers should be fine.

When you start adding multiple amps or dedicating an amp to driving a specific type of
speaker (like a subwoofer), that's when you'll need a more sophisticated crossover.

A high-pass filter allows only frequencies above a given point to pass through. A low-
pass filter allows only frequencies lower than a given point to pass through. High- and
low-pass filters can be used together to create what's called a "bandpass" that will allow a
certain band or range of frequencies reach a speaker.

In a hypothetical car audio system the audio frequencies might be directed as follows:
Low frequencies (say 100 Hz and lower) go to subwoofers.
Midbass speakers get frequencies between 100 and 250 Hz.
Midrange speakers would see frequencies between 250 and 3,000 Hz.
All frequencies above 3,000 are handled by the tweeters.

Keep in mind that the points listed here are not set in stone and do not apply to every car
out there. The best crossover points for one vehicle might not be the best for another. It
all depends on the speakers being used and the acoustic properties of the car. Most
electronic crossovers allow you to choose from several crossover points.
back to top

Q: What's the difference between passive and active crossovers?
                                                                                             26



A: There are two types of crossovers — "passive" and "active" (also referred to as
"electronic"). A passive crossover is basically a capacitor or coil installed on the speaker
leads between an amplifier and a speaker. It sets up a roadblock to stop certain
frequencies from reaching the speakers. Passive crossovers are relatively inexpensive and
easy to install. Their primary disadvantage is that they tend to make your overall system
slightly inefficient because they filter out signals that have already been amplified.

Your system will perform better and be more efficient using an electronic crossover,
especially if you're running multiple amps. An electronic crossover is installed between
your receiver or equalizer and your amplifiers. It filters and directs the frequency bands
in the low level signal before they reach the amplifiers.

Active crossovers are usually adjustable (you can select the crossover points) and often
have other features like bass boost circuits and phase switches for subwoofers. Another
bonus when using an electronic crossover is that you can independently control the
relative volume of different types of speakers.
back to top

Q: How hard is it to install a crossover?

A: Passive crossovers are very simple to install. They do not require a power connection,
a turn-on lead, or grounding. All you have to do is tap into your speaker wires between
your amp and speakers. If you're using one of our Tri-Way Crossovers to drive two
speakers and a subwoofer, simply connect speaker wires from the amp to the input side of
the crossover and then run speaker wire from the output side of the crossover to the
speakers and the subwoofer.

Active crossovers require a bit more planning and time, but with a little effort, almost
anyone can get the job done. You'll need to provide 12-volt power from your car battery
to operate the crossover just as you must provide a 12-volt source of power to your amp
or amps. An electronic crossover also requires a turn-on lead to trigger it when you power
up the receiver. And of course, you'll need a solid, noise-free grounding point.

You'll route the audio signal from your head unit or equalizer to the inputs on the
crossover via RCA patch cables. You then run patch cables from the crossover outputs
(frequencies have been properly channeled to each output at this point) to the proper
amplifiers.
back to top

Q: What does the phase switch on an electronic crossover do?

A: It's important to understand the difference between a reversal in "polarity" and a
reversal, or change, in "phase." Polarity problems are usually caused by the positive and
negative speaker wires being hooked up backwards on a speaker. They should be
corrected by connecting the speaker wires properly.
                                                                                            27



Phase switches on electronic crossovers are meant to deal with a change in signal phase
caused by an electronic crossover. An electronic crossover will alter the phase of the
output signal by 90 degrees for every "order" of slope that the crossover uses (i.e. a 6
dB/octave, or 1st order, crossover will skew the output phasing by 90 degrees, a 12
dB/octave slope, 2nd order, will skew it by 180 degrees, and so on).

The phase switch on an electronic crossover usually changes the phase of the output
signal by 180 degrees. Depending on the interior dimensions of your vehicle, how the
subwoofer is mounted, and where it is mounted, the bass may sound better if the phasing
switch is utilized. Sometimes it will sound better if it is not used. The higher the
crossover frequency between the subs and the mid-bass, the more noticeable the
difference caused by phase switch position.
back to top

Other Effects Units

Reverb
Reverberation (reverb for short) is probably one of the most heavily used effects in
music. When you mention reverb to a musician, many will immediately think of a stomp
box, signal processor, or the reverb knob on their amplifier. But many people don't
realize how important reverberation is, and that we actually hear reverb every day,
without any special processors.

What is Reverberation?
Reverberation is the result of the many reflections of a sound that occur in a room. From
any sound source, say a speaker of your stereo, there is a direct path that the sounds
covers to reach our ears. But that's not the only way the sound can reach us. Sound waves
can also take a slightly longer path by reflecting off a wall or the ceiling, before arriving
at your ears, as shown in Figure 1. A reflected sound wave like this will arrive a little
later than the direct sound, since it travels a longer distance, and is generally a little
weaker, as the walls and other surfaces in the room will absorb some of the sound energy.
Of course, these reflected waves can again bounce off another wall before arriving at
your ears, and so on. This series of delayed and attenuated sound waves is what we call
reverb, and this is what creates the 'spaciousness' of a room.


Figure 1: Sound waves travel many different paths before reaching your ears.


It's very tempting to say that reverb a series of echoes, but this isn't quite correct. 'Echo'
generally implies a distinct, delayed version of a sound, as you would hear with a delay
more than one or two-tenths of a second. With reverb, each delayed sound wave arrives
in such a short period of time that we do not perceive each reflection as a copy of the
original sound. Even though we can't discern every reflection, we still hear the effect that
the entire series of reflections has.
                                                                                           28



So far, it sounds like a simple delay device with feedback might produce reverberation.
Although a delay can add a similar effect, there is one very important feature that a
simple delay unit will not produce - the rate of arriving reflections changes over time,
whereas the delay can only simulate reflections with a fixed time interval between them.
In reverb, for a short period after the direct sound, there is generally a set of well defined
and directional reflections that are directly related to the shape and size of the room, as
well as the position of the source and listener in the room. These are the early reflections
(also called the 'early echoes' despite the general meaning of the word 'echo'). After the
early reflections, the rate of the arriving reflections increases greatly. These reflections
are more random and difficult to relate to the physical characteristics of the room. This is
called the diffuse reverberation, or the late reflections. It is believed that the diffuse
reverberation is the primary factor establishing a room's 'size', and it decays exponentially
in good concert halls. A simple delay with feedback will only simulate reflections with a
fixed time interval between reflections. An example impulse response for a room is
depicted in Figure 2. (For those who are not sure what an impulse response is, think of it
like this. If you consider a small piece of a sound, each vertical line marks when that
same piece of sound is heard again, and the height of the columns is how loud the sound
is at that time.)



Figure 2: Impulse response of a room.
Another very important characteristic of reverberation is the correlation of the signals that
reach your ears. In order to give a listener a real feeling of the 'spaciousness' of a big
room, the sounds at each ear should be somewhat incoherent. This is partly why concert
halls have such high ceilings - with a low ceiling, the first reflections to reach you would
have bounced off of the ceiling, and reach both of your ears at the same time. By using a
very high ceiling, the first reflections to reach the listener would generally be from the
walls of the concert hall, and since the walls are generally different distances away, the
sound arriving at each ear is different. This characteristic is important for stereo reverb
design.

A measure that is used to characterize the reverberation in a room is the reverberation
time. Technically speaking, the reverb time is the amount of time it takes for sound
pressure level or intensity to decay to 1/1,000,000th (60 dB) of it's original value (or
1/1000th of it's original amplitude.) Longer reverberation times mean that the sound
energy stays in the room longer before being absorbed. Reverberation time is associated
with what we sometimes call the 'size' of the room. Concert halls have reverberation
times of about 1.5 to 2 seconds.

The reverberation time is controlled primarily by two factors - the surfaces in the room,
and the size of the room. The surfaces of the room determine how much energy is lost in
each reflection. Highly reflective materials, such as a concrete or tile floor, brick walls,
and windows, will increase the reverb time as they are very rigid. Absorptive materials,
such as curtains, heavy carpet, and people, reduce the reverberation time (and the
                                                                                            29


absorptivity of most materials usually varies with frequency). You may be able to this
notice difference on a gig. During the sound check, the room will sound 'bigger', but
during the actual performance, the room may not sound as empty. People tend to absorb
quite a bit of energy, reducing the reverberation time. Bigger rooms tend to have longer
reverberation times since, on the average, the sound waves travel a longer distance
between reflections. The air in the room itself will also attenuate the sound waves,
reducing the reverberation time. This attenuation varies with the humidity and
temperature, and high frequencies are affected most. Because of this, many reverb
processors incorporate lowpass filters.

Since we are so accustomed to hearing reverberation, we often have to specifically listen
for it in order to notice it. Probably the best way to notice reverb is to listen after short,
impulsive sounds, while the sound is still bouncing around. If you want to test out the
reverb in various rooms of your house or apartment, clapping your hands works pretty
well. Sound Set 1 presents a dry sound (no reverb) and the same line with reverb added.
Listen just after the accented notes.

Why use Reverb?
If reverb is always around us, why do we add reverb to recorded sounds? Well, many
times we are listening to music, we are in environments with very little or poor reverb.
The reverberation in a car for example, may not be sufficient to create the majestic sound
of a symphony orchestra. And when using headphones, there is no reverberation added to
the music. A very dry signal can sound quite unnatural. Since we can't always listen to
music in a concert hall or other pleasing environments, we try to add reverberation to the
recording itself.
To add reverb, one could make the recordings in a highly reverberant room such as a
concert hall, but this is often impractical since such rooms may not be easy to access, be
located far away, or too expensive to use. This has caused the development of a variety of
ways to synthetically add reverb to recordings.
                                                                                           30



Chapter --: Speakers
   Speaker Enclosures: Choosing and Building, Powered and Non-powered Subwoofers
   Speaker Connectors
   Speaker Baffles
   Bass Blockers
   Speaker Basics
   Speaker Action
   Speaker Components
   Speaker Classifications (by frequency)
   Speaker Specifications
   Speaker Size
   Speaker Wire
   Magnets
   Voice Coils
   Dual Voice Coils
   Speaker Cones
   Tweeter
   Midrange
   OEM
   Multiple Speaker Systems
   Multiple-Driver Speakers
   Stereo
   Surround
   Full-range Speakers
   Woofers
   Subwoofers
   Suspensions
   Speaker Basket
   Midbass
   Input Sensitivity
   Response
   Nominal Power Handling
   Peak Power Handling
   Speaker Polarity
   Impedance and Interconnecting Speakers
   Connecting speakers in parallel
   Connecting speakers in series
   Connecting speakers together in series and parallel
   Connecting dual voice coil speakers



 speakers are often referred to as "drivers," because this is actually the correct term. The
term "speaker" is traditionally meant to describe what you may think of as a cabinet or
system with speakers/drivers built in, whereas the term "driver" refers to an individual
                                                                                        31


speaker. In some cases, speaker/drivers may also be referred to as "emitters" or
"transducers," both technically correct terms.

Choosing Speakers

How SpeakersWork

What's A Woofer?

What's A Midrange?

What's A Tweeter?

How to calculate impedance

What Are Two-Way, Three-Way, & Component Speakers, Dual-Cone, Dual-Voice-Coil
& Full-Range Speakers?

What's A Crossover

Understanding Theile/Small Parameters

Selecting The Right Speakers
(And The Left Ones Too)


the woofer determines all parts of the sytem. Base your decision about amplifiers and
enclosures around the woofer or speaker you select.

5 levels:

Big and Loud Bass System

For most cars, 10, 12 or 15" subwoofers mounted in a heavy dual bandpass or sealed box
and connected to compatible 500 to 2400 watt (RMS) amplifiers

Look for woofers that have dual voice coils with 4 ohm impedance, and between 300 to
1500 watts RMS total.

The best performing and most efficient systems will often have dual 4 ohm woofers with
all coils connected in parallel to form a 1 ohm total mono load. This will require a 1 ohm
compatible mono amplifier with a capacity equal to the the total RMS power rating of the
woofers, plus 5 to 30 percent more as an overhead to allow high transients with minimal
distortion.
                                                                                           32


The amount of power (in RMS watts) determines how much clean loudness the system
can provide.

Power is exponential in relation to loudness, which is linear. This means that for a 10
watt system to produce twice it's clean power, output must increase to 100 watts.

twice the loudness again requires 1000 watts, and so forth.

Systems of more than 500 watts RMS are fairly typical

Less expensive setups, with smaller speakers and less powerful amps can provide good
volume and bass as well, provided the components of the system are compatible.


Most OEM systems are adequate for basic listening habits. New speakers to replace the
OEM might be all that’s needed, especially in older cars.

Adding small front or dash mounted mid range units will provide enough loudness and
bring out the mid-range frequencies heard in genres like jazz. For more bass response
with these kinds of speakers, add a small (75 to 100 RMS watt-per-channel) amplifier
and add a small (8" to 10") single subwoofer (usually installed under or behind the back
seat).

A small pair of tweeters might be all that’s needed to bring out the high frequencies and
can be mounted on the dashboard.

Speakers as Motors
Loudspeakers are really very simple devices from an operational standpoint. An amplifier
generates electrical energy that alternates constantly from positive to negative in a pattern
of waves that vary in size and frequency.

The output from the amplifier is connected to the speaker at the Terminal Strip. There is a
fine braided wire that carries the signal from the terminals on the frame to the conductors
on the cone leading to the Voice Coil Assembly.

These wires are extremely flexible, to enable the Cone to move back and forth without
restriction or stress, and to do so without breaking.

The Voice coil itself is mounted on a rigid cylinder in the center of the cone. All the
moving parts operate as a single unit, moving back and forth in the magnetic field, and
are suspended by the surround, or outer edge of the cone at the front, and by the "Spider"
support at the rear.

At it's natural resting point, the voice coil is centered within a narrow magnetic Field
Gap. This gap constitutes the north and south poles of the Magnet Structure, whose
                                                                                            33


energy is derived from a powerful permanent Magnet sandwiched between the two pole
pieces.

Essentially, the speaker operates by responding to positive and negative waves from the
amplifier, passing through the voice coil, causing it to be moved back and forth by
attraction and repulsion within the high-gauss flux density of the intense magnetic field.

Since the voice coil is rigidly mounted to the cone, the resulting energy is transmitted to
the cone producing a piston like motion that alternately compresses and evacuates the
adjacent air mass, thus producing sound. These are the essential acoustical-electrical
principles underlying all electro-dynamic sound transducers.

The operating principles that make a typical speaker work today are identical to those
used a hundred years ago. The most obvious difference between those first speakers and
new ones today is the replacement of the electrical field coil used to create the magnetic
field in the early units with a more powerful, permanent (non-electrical) magnet made
from highly refined metallurgical materials.

Gauss density, which is a measure of the strength of magnets, is many times higher in
modern alloys.

The higher the gauss density, the greater the field strength.

This is the force within the speaker motor that principly determines the amount of power
from the amplifier that the speaker will be able to handle.

Another important factor used to assess power handling, is the weight of the magnet
itself, which usually has a bearing on the amount of magnetic energy it can produce.

INSERT Tip: In evaluating speaker specifications, some manufacturers specify weight
for the magnet only, while others weigh the entire magnet structure, which may be up to
twice the weight of the magnet proper.

Another important parameter is the material of which the magnet is made. Newer
speakers have magnets made of neodymium, strontium, and barium, among other
technologically advanced metal composites. Older and cheaper units use alnico 5 and
other less dense alloys that may have only one third or less of the magnetic potential of
the newer composites.

Woofer
Woofers are loudspeakers designed to reproduce the lowest frequencies, or bass end of
the audible sound spectrum.

They may be anywhere from 4" in diameter all the way up to huge 36" giants meant for
highly specialized scientific purposes.
                                                                                            34


For most consumer purposes however, sizes are pretty much standardized at 4, 5, 6, 6.5,
8, 10, 12, 15, and 18 inches, with the 6.5 to 12 inch sizes being the most popular.

Because woofers are specialized reproducers, their design maximizes their potential for
reproducing the lowest frequency. Thus they will have cones that are suspended in such a
way as to promote the maximum back and forth motion, called XMAX.

Middle frequencies by contrast, have smaller cones and less excursion, or cone travel.

Tweeters have cones, domes, or diaphragms that may seem practically motionless. Even
so, they can produce sound in their frequency range that is just as powerful (and piercing)
as their larger siblings.

Woofer cones must move in and out with the longest possible extension because sound
waves get longer as they get lower in frequency.

Current technology provides us with stiff and rigid cone materials such as Polypropylene,
Carbon and Polymer Laminates that maintain their shape under stress, resist moisture,
and are very light.

The cone works as a piston to compress and alternatively evacuate large masses of air. To
do this most effectively, the woofer must be connected to an amplifier that produces the
high amplitude waveforms that can produce this motion.

Because such signals require considerable electrical power behind them to control the
cone movement, the highest power available is needed strictly for bass reproduction.

Similar levels in the midrange and high frequency areas require comparatively little
power for the same apparent loudness, all other things being equal.

Because of the powerful dynamic motions of the woofer cone, the frame or basket is
often cast in a heavy metal to reduce the tendency for the speaker to "ring" at certain
resonant frequencies.

This arrangement also allows for the most precise alignment of the voice coil within the
magnetic field and is particularly useful in speakers at or greater than 15" in diameter.

In the larger drivers, after years spent resisting the tug of gravity, there is a tendency for
the heavy magnet to be pulled out of alignment on the stamped frames of the larger sizes.
This is of little practical concern with 12" and smaller woofers.

High power woofers often have dual voice coils in vertical arrangement on the cylindrical
former. These allow different impedance configurations to be used. With two 4 ohm coils
in two woofers, a parallel circuit can be used that creates a total mono impedance of 1
ohm. This is a very efficient arrangement to transfer energy from a compatible amplifier.
                                                                                          35


Magnetic structure design is fairly standardized with pole pieces constructed to put a
concentrated magnetic field around the voice coil or coils.

Over the past 30 years, the magnetic materials used have changed considerably to permit
ever-larger concentrations of magnetic energy rated in "Gauss" to be created from smaller
quantities of lighter compounds.

Coupled with the use of Kapton multiwound coils and more powerful amplifiers,
speakers - when designed with even a modicum of commitment to high fidelity - can
much more easily achieve that end.

For speakers to truly work well and achieve their maximum audio potential, they must be
housed in an appropriate enclosure.

Indeed without some elementary means of preventing the front radiated wave from
interacting with the back wave, no bass would be heard at all. This is simply because the
two waves are precisely 180 degrees out of phase with each other and cancel out when
they meet.

Speaker Boxes and Enclosures

Midrange
The midrange of the sound spectrum is of critical importance, as this is where the heart of
the music lies. Vocals and instruments should sound natural and detailed, not too
prominent or recessed, nor too bright or too dull.

A midrange speaker is usually much smaller than a woofer, but with a radiating surface
area greater than the typical tweeter.

It reproduces the mid frequency range from approximately 300 to 5000 Hertz.

This operating range can vary considerably from one driver to the next, thus giving the
system designer more flexibility in choosing crossover points for the other drivers.

Since the midrange, like the tweeter, is designed to produce optimum response with much
less power than is required for the woofers, the magnet structure is usually quite a bit
smaller, and the rated power handling is also much less.

But since it must be isolated from the direct current of the amplifier by the crossover
circuitry, this should not effect the speakers over-all power handling performance.

Dispersion - the extent to which a sound emitter yields acoustic radiation over a given
area - is a particular concern in midrange speakers, whose portion of the audio spectrum
has a much more directional character than woofers. Midrange drivers mounted in
enclosures with woofers will usually have a closed back design, to prevent interference
                                                                                           36


from the woofer's internal backwave. Such interference is usually a source of
intermodulation (IM) distortion.

In a typical car system you might see a woofer in a box in the rear, tweeters mounted on
the dash panel, and midrange speakers in the side or door panels.

In surround applications, midrange and tweeter drivers carry all the directional source
information.

Three-way or triaxial speakers take the separate woofer and tweeter from a two-way
design and add a dedicated midrange driver. This arrangement can produce a more
uniform response, depending on how well it is designed. With the inclusion of a
midrange driver in any system, the design of the crossover must be more precise.

Tweeter
Highs are reproduced by the tweeter, a small driver separate in many systems, but
mounted in front of woofer cones in multidriver 2 and 3 way car speakers.

Tweeters provide the sizzle and sibilance that give a more lifelike sense of presence to
the experience of music.

They come in three common types: Cones, Domes, and horns.

Tweeters usually do not require very much power to create relatively loud sound. High
frequency wavelengths are quite small and only a few watts can generate piercing levels
of sound.

Compare the tweeter whose radiating surface seems almost rigid, to a typical woofer
where the cone may move up to 2 inches.

Cone tweeters are efficient and the most economical. They have a limited dispersion
pattern.

Dome tweeters are the type found in most home speakers. They have a more linear
response and are more accurate. They also have a much wider dispersion pattern than any
other type. Some domes are made of metals like neodymium or titanium that yield
extended high frequency response. Others are made of Mylar, or a fine cloth like silk for
a less extended but somewhat more linear, smoother sound. Some are made from a
combination of materials.

Horn Tweeters are powered either by a dynamic (magnet and coil) diaphragm, or by a
Piezo driver. They are the most powerful high frequency emitter but more directional,
and may lack the extended range of the domes.

A typical car system might consist of a woofer in a box in the rear, midranges at the side
and tweeters mounted on or in the dash panel.
                                                                                           37



Diaphragm
This term describes the sound-producing element in a tweeter or horn and is the surface
that produces the sound you actually hear. The motor that drives it can be any of several
technologies including Piezo, conventional dynamic, or ribbon types. Diaphragms do not
produce bass and low midrange frequencies well, so they are not usually found in those
applications.

Dispersion
The extent to which a sound emitter yields acoustic radiation over a given area,
dispersion is a particular concern in tweeters whose portion of the audio spectrum has a
much more directional character than woofers. Many horn tweeters, while very
energetic, have a more limited area of dispersion within which their effect can be fully
perceived. Generally, dome tweeters can be heard over a much wider area, all other
factors being equal.

Dome Tweeters
Tweeters are of several different types; cones, horns and domes being the most popular.

Dome types are heavily favored in many standard applications. They are efficient, and
have low Distortion and wide dispersion. There is a choice between hard and soft dome
materials, but all have relatively low mass and high power handling capabilities.

Hard Dome Tweeter
A characteristic of some Dome tweeters in which the dome is made of some light, hard
metal such as neodymium, and titanium as well as some of the more rigid plastic
compounds. The differences in reproduction between hard and soft dome tweeters are
present, but very subtle. The essential difference is in the higher frequencies that are often
reproduced by hard domes, up to 25 kHz or more. Since many people tend to have
acoustic sensitivity that is sharply reduced or rolls off at 12 to 15 kHz, this may not be an
advantage.

Silk Dome Tweeter
Dome tweeters in which the dome is composed of a treated soft silk like material. This is
a design that is much less susceptible to mechanical deformation, and yet yields a fairly
smooth response over the extent of its range.

Piezo Tweeter
A tweeter whose motor is simply a crystal of Piezo material through which the signal
current flows. The crystal lattice responds to this by bending in proportion to the
Amplitude and frequency of the incoming signal. Piezo tweeters are very efficient
drivers and are relatively inexpensive. They come in a large variety of designs and
radiators. As a high impedance device, no crossover is needed in most cases.

Horn Tweeter
                                                                                            38


A driver consisting of a relatively small emitter at the apex of a curvilinear or exponential
horn.

This is an effective system for radiating high frequencies in a variety of situations. The
size and shape of the horn will usually dictate the pattern and use of the driver. Long
horns with narrow apertures, tend to have the narrowest radiation pattern, and are very
useful in large listening rooms, especially where highly directional effects, such as
surround sound requires, are desired.

Shallower versions, with wider radiation patterns, have more general applications,
especially in car stereo applications where a wider field of coverage is desired, along with
a robust driver that can withstand severe environments. In such situations, a Piezo driven
emitter (driver) is highly desirable for its ability to handle high-energy inputs on a
variable basis.

Bullet Horn Tweeter
A type of Dome tweeter in which the radiator has a large passive, bullet-shaped device
above its center that extends the nominal dispersion angle of the sound so that it covers a
greater area with a relatively small driver.

Super Tweeter
A driver constructed to reproduce the highest possible frequencies from roughly 10 kHz
to well beyond the usual threshold of audibility, 25 kHz and up.

While most standard Tweeters can do an excellent job right up to 16 or 20 kHz, these
units deliver the most extreme parts of the upper range for those fortunate (or not) few,
who can actually hear them.

Two-Way
Music can be reproduced with reasonable accuracy by two-way, or coaxial, designs.
These speakers use a separate crossover and tweeter to deliver high frequency
reproduction that surpasses that of single cone or dual-cone "extended range" models
with whizzer cones.

The tweeter, usually a cone or a dome, is mounted either on a post or bridge inside the
front of the woofer cone.

Three-Way
Three-way or triaxial speakers take the separate woofer and tweeter from a two-way
design and add a dedicated midrange driver for enhanced coverage of the vital middle
frequency area.

The filling effect of this extra mid-frequency energy can also boost overall uniformity.
                                                                                             39


Four-Way
Four Way speakers add a small "super tweeter" to extend the high range frequency
response out to 22 to 25 Kilohertz. This is not so advantageous as it might seem. Very
few people can hear sounds above 15 kHz, and in a relatively noisey car environment,
such sounds could easily be obscured by road and ambient car noise.

Bridge and Post Mounted (2 & 3-way speakers)
In combined 2 and 3-way speakers, which have woofers together with a Tweeter, or a
Tweeter and a Midrange driver, the smaller drivers are attached to the woofer by either
one of two standard mountings:

The bridge-mount method has a metal or plastic bridge running from one side of the
woofer's outer perimeter to the other. The smaller driver or drivers, together with the
crossover network, is then mounted on the bridge. The advantage of this arrangement is
that the woofer center dome is left intact with no exposure of the voice coil or other
internal elements. On the negative side there is more covered surface area that marginally
reduces the output at certain frequencies, and it may be little more difficult to mount the
unit.

The post-mount method provides a post that is attached to the center of the inner magnetic
pole, to which the other drivers are then mounted. It has a reduced obstruction to woofer
dispersion, but it can require a hole in the dust cover/cap that could give environmental
access to the woofer's inner workings. This creates the possibility of operational
degradation from accumulations of dust over time, unless a flexable cover is provided.

Component Speaker Systems
This term is used to indicate a system in which separate mounting arrangements are
provided for each component of the system.

In a typical car system, you might see mid or full range drivers at the side, and tweeters
mounted on the dash panel.

A pair of crossover circuits delivers separate signals to each driver.

In some arrangements, a bass system driven by its own amplifier compliments and
completes the system.

This compares to the typical integrated speaker enclosure in which all the drivers are
mounted in the same box or assembly.

Capicitors
If your lights dim with the beat, or your speakers start smoking without permission, or
your CD skips a beat or two, your amplifier may be trying to use more fast energy than
the electrical system can supply.
                                                                                            40


Unfortunately, your car's electrical system is not thinking about the needs of your
amplifier.

Power is being robbed from your audio system by such trifling matters as the engine and
lights.

This may leave your amplifier hungry for power, and worse, delivering destructive
distortion when it fails to get it.

Understand of course, that no capacitor is a substitute for an adequate amplifier to
provide the amount of bass energy you want to project.

Nor will it substitute for an inadequate car power supply.

You may have to install a stronger alternator if you have one of the more powerful
systems.

The rest of your system must also be "up to spec" to serve that purpose.

Technically, a capacitor is an electronic device which consists of two rolled up plates of
electrically conductive material separated by an insulator known as a dielectric.

Within this frame an electrical field charge is developed. The quantum of this charge is
the capacitor's value, measured in farads. It is largely determined by the surface area of
the plates, the effective distance between the plates, and the chemical composition of the
dielectric material.

Audio capacitors are energy reservoirs that store the necessary power your amplifier will
need to punch those big bass notes while limiting clipping.

Define “clipping”

They store power during intervals when it is not required, which is most of the time, and
release it when a short term transient demand exceeds what is available from the car's
power system.

A stiffening capacitor for your amp is the simplest way to be sure your system always
gets every bit of immediate current it needs.

From the smallest .5 farad, to 10 farads, there's a capacitor suitable for your installation.

Mount them as close to the amplifier as possible, and use at least .5 farad (500,000
microfarads) per 500 watts RMS of power output.

Using more will not cause problems.
                                                                                               41


On the other hand, it will not contribute to the operation either, and it's easier on the
wallet to just get what you need.

Many capacitors are rated for ESR. This is the Equivalent Series Resistance of a
capacitor.

A perfect capacitor would have only capacitance. All conductors have resistance.

In a capacitor, there are many conductors such as terminal leads, foil and even the
dielectric electrolyte.

The resistance of all of these conductors contribute to the capacitor's series resistance.

It's essentially the same as having a resistor in series with an ideal capacitor. Capacitors
with relatively high ESR will have less ability to pass current from its plates to the load
(the amplifier).

Discharging the Capacitor
If you plan to remove your capacitor for any reason, you may want to completely
discharge the capacitor to avoid a potential hazard.

To discharge the capacitor (only after it's disconnected from the system, of course), will
need to enable the current to flow from one terminal to the other. You can use either a
test light or resistor for this purpose. Some large capacitors tend to develop a charge
similar to a battery and will produce a small voltage across its terminals.

Since, in a large capacitor (over .5 farad), even a small voltage could be dangerous. After
it is discharged, you may want to connect the terminals together with a piece of wire or
resistor. Even if the capacitor design doesn't permit it to develop adverse voltages when
unused, leave the terminals connected as a visual confirmation of the unit's safety.

Charging with a Resistor
Many capacitors will need to be initialized with a 10 to 50 ohm resistor connected to the
power main for usually 8 to 25 seconds depending on the size. After charging is
completed, connect the power main carefully.


Crossover
In all speaker systems, regardless of how many drivers are operating, it is desirable to
have a smooth, linear response, with as few peaks and valleys as possible.

Since woofers have an extremely attenuated response in the high range and tweeters can
be destroyed by powerful low frequencies, a crossover circuit is used to isolate, optimize,
and integrate the drivers.
                                                                                           42


A crossover is an electronic or mechanical means of separating frequencies in the audio
range so that they can be rendered most efficiently in a multi driver system.

There is normally, one passive crossover in each cabinet. In less expensive speakers, this
means that the tweeter may be efficiently isolated from the woofer through a High Pass
Filter, usually a single capacitor that limits the low frequencies and passes on the high
frequencies delivered to the tweeters and midranges, from the amplifier.

Another popular alternative is the Active Electronic Crossover in which the crossover
action takes place in a unit positioned before the amplifier in the circuit.

This requires the use of two or more amplifiers, each connected to the particular drivers
(midranges and or tweeters) whose frequencies are delivered by the electronic crossover.
This is a much more expensive, but very efficient, way to achieve the desired result.
Individual speakers that have separate inputs for the various drivers are said to be
Biamplified.

The term 'Crossover' indicates that point on the normal frequency spectrum between 20 to
20 thousand Hertz, (or cycles per second) where certain frequencies are muted, or rolled
off to one driver and permitted passage to another.

Thus, in a typical 3-way crossover, frequencies from 5, up to 1800 Hertz (Hz) or so, are
filtered and diverted to the woofer.

Frequencies above that are sent to the Midrange up to 3500 Hz or so, and muted above
that.

Frequencies above the midrange band are filtered out and the remaining high frequencies
are passed to the tweeter.

A mechanical crossover is typically a small dome or cone affixed to the center of a
woofer that extends it's high frequency response, so that it becomes a so-called full range
speaker.

Electronic crossovers connected to independent tweeter and midrange drivers usually are
much more effective in isolating the frequency bands within a spectrum, and at the same
time, reduces intermodulation and other forms of distortion.

Passive electronic crossovers can be 2, 3, 4-way or more. They are circuits that for the
most part, use passive components such as coils (MH), capacitors (MFD), and resistors
(Ohm).

One example of a configuration is where the woofer is connected directly to the amplifier
and all the crossover action is applied to the tweeter. However, while this may work fine
for certain types of 2-way speakers, the exact value, number, and configuration of the
                                                                                              43


electronic components are contingent upon the particular drivers used and the cabinet
characteristics of the speaker as a whole.

No crossover (passive or electronic) should be seen as providing rigid frequency dividing
lines.

In a simple two way design (one woofer and one tweeter) the designer might set a
crossover point of 1800 hertz (also written as 1.8 kHz or 1800 cycles per second [cps]).

This does not mean that all of the energy above 1800 Hz are sharply routed to the tweeter
while only frequencies below, go to the woofer.


There is actually a gradient, or slope up or down from the attenuation point.

In fact, in some low budget designs, there is no upper frequency roll-off limitation for the
woofer, beyond it's own natural response roll-off.

This means that for at least one octave of sound above and below the 1.8 kHz example
frequency, (1 kHz to 4 kHz) the sound from the two drivers will intermingle and may
cause interference.

This can be either constructive or destructive interference; the knowledgeable designer
takes this into account by utilizing not just the response curves of each driver, but their
roll-off characteristics as well.

If the woofer and tweeter both have a peak of 3 dB at the same frequency, they could
combine at this one point in the frequency band to make the sound "harsh".

Conversely, if the speakers canceled each other (i.e. one peaked while the other dipped,
thus nullifying that particular frequency), some of the important midrange frequencies
would be lost, making the sound a lot quieter, thinner and less present.

Thus, it is important to understand the characteristics of any replacement parts and how
well they will integrate with your existing system, before they are put into your speaker.

However, and this is important, while this information could be very useful in helping
you optimize your system, it is also very difficult to come by.

Most car audio manufacturers do not provide the kind of detailed technical analysis that
makes it possible for the average audiophile to achieve optimal results.

Thus, most of us make do with replacing defective units with drivers that are most similar
to the original parts. Even though this method is obviously not as precise, the overall
results are usually quite acceptable. This is one reason why most drivers should be
                                                                                                44


replaced in pairs, (or four's, with surround systems) thus avoiding obvious imbalances on
the sound stage.

Equalizer
It is virtually impossible to reproduce the complex timbre of music in exactly the way it
was created in the recording studio. Every loudspeaker is a unique instrument of
reproduction that is inherently incapable of reproducing every part of the sound spectrum
with equal intensity. In multiple speaker systems, things are even more complex because
different drivers interact with each other.

Equalizers offer the capability of both compensating for defects and fine tuning the
system.

With an equalizer, certain frequency ranges can be either increased or cut, to shape the
overall sound spectrum to compensate for defects in the original soundscape, or to bring
out certain instruments, or simply as an expression of the listener's preference.
While the accuracy of high fidelity remains the goal, many listeners strive for more
accurate reproduction, and then add bass for a fuller, more "dynamic" sound.

Electronically, the equalizer is situated on the line feed between the receiver and the
amplifier.

Because it modifies low level high impedance signals only, it is less vulnerable to
electrical overloads than the amplifier, and is overall less likely than either the receiver,
or the amp to create problems.

Of course, as with any piece of electronic circuitry, a fault may develop; it's just less
likely.

The number of bands in an equalizer controls how finely the frequency pattern can be
amplified or attenuated. Three to 30 bands or more can be provided by available
equipment.

A typical 10 band equalizer configures the available audio range into 10 parts and the
levels of any one of them can be adjusted discreetly according to the Q of the design.

The Q of an equalizer describes how wide a range each adjustment has.

If a specific band is labeled as 100 Hz a high Q equalizer will only boost or cut
frequencies right around 100 Hz and not really affect signals at 80 Hz.

A low Q equalizer generally affects a wide range of frequencies even though it may be
centered at one specific one.

Typically, the more bands in the EQ, the higher the Q, so the different bands are not
affected by each other.
                                                                                            45



Simple bass and treble controls have the lowest Q.

Equalizers with only few bands are good for making general adjustments but not helpful
for the finer gradients.

Another key distinction is the degree of effect, rated in decibels, which each adjustment
either boosts or cuts the center frequency it controls.

A typical value is probably 10 dB, with many choices available in the 8 to 15 dB range.

This means that each control will minimize or maximize the relative level of its
frequency by +10 dB, or - 10 dB from the center, which is the unmodified position.

Keep in mind of course, that this is a relative value.

If all the controls are raised or lowered at the same time, and by the same amount, then all
we have is just a large and expensive volume control.

A 30 band equalizer is great for making precise adjustments. A real time analyzer (RTA)
oscilloscope is used in calibrating the effect of these equalizers. The RTA produces a flat
pink noise signal and shows the technician how the system responds in acoustical effect.

The equalizer is adjusted until the RTA verifies the desired response. This desired
response is rarely linear because most listeners prefer a more dynamic pattern, with more
bass emphasis. If you must have a 30 band equalizer, then having a high degree of
technical knowledge is essential to getting the most out of it..

An equalizer's capabilities are especially useful when dealing with poorly recorded, non-
linear analog recordings, or if the "mix" selected by the original recording engineer does
not quite suit your taste.

But with most modern digital, full range, linear recordings, the sonic limitations of the
analog era no longer mandate the use of an equalizer to acheive a high fidelity result.

Many people find that as a general practice, equalizers can be left out of the system with
not too much loss of control.

The simple bass and treble tone controls on most receivers provide all the shaping
capabilities needed most of the time.

However, many vehicles have a natural resonance frequency between 100 and 200 Hz,
and road noise occurs between 25 and 200 Hz. So even an otherwise perfectly balanced
system may get competition at these resonant frequencies, exaggerating them in a way
that can muddy sound and mask other frequencies.
                                                                                        46


If this is a noticeable problem, a graphic EQ can be used to overcome this interference by
adjusting the affected bands to compensate.
                                                                                  47



Chapter --: Installation Overview
Car Manufacturers: Matching audio systems with car make and model (see Crutchfield)
Help from Auto Manufacturers
Uninstalling OEM
Help from local Installation Services
Head Unit
Speaker
Speaker Enclosures
Enclosure materials
Alternative enclosure materials
Speaker enclosure shapes
Speaker enclosure damping
Speaker enclosure designs and techniques
Closed-box enclosure
Aperiodic enclosures
Ported-box enclosures
Transmission-line enclosures
Theil/Small Parameters (specifications for building speaker systems and enclosures)
Working with Plywood
Working with MDF
Fiberglass
Working with Fiberglass Resin
Working with Fiberglass Compound
Making Speaker Baffles and Odd-shaped enclosures
Coatings
Grille Cloth and Metal Grilles
Lexan (Polycarbonate) and Plexiglass (Acrylic) sheets
Panels
Subwoofer boxes
Veneer
Vinyl and Carpeting
Other Finish Materials
Subwoofer
Amplifier
CD Changer
Video
Mounting kits
Universal Mounting Kits
Wiring harnesses
Wire (Shape, Style, Type, Color code, Gauge, Connecting, Connectors, Soldering)
High-end Audio Wire/Cable
Connectors
Power Cables
Fuses
Ground Wires
                                                                                           48


Noise
Soldering
Antenna Adapters
Auxiliary Input Adapters
Tools
Troubleshooting (Poor sound, noise, hot amplifier, speaker damage, faulty connection)
Repairs


Installation of the various components used in car audio systems ranges from amateur to
professional, simple to complex. Advanced installation is not covered in The Savvy
Guide to MP3s in the Car, but a solid introduction is provided. For instance, building
and installing speaker enclosures requires advanced knowledge of audio, acoustics, and
working with wood, plastic and other materials. Plus, not all enclosures are created equal
and vary considerably depending on car make and model.

If installation is not “Plug and Play” or near it, it’s best to seek expert advice. But car
enthusiasts have been customizing their cars ever since cars were invented and installing
advanced audio systems is not entirely out of reach for the average music fan.

Advanced installation guides, especially for ampifiers, speakers, and crossovers, require
extensive photos and graphics to be effective. Even still, photos are insufficient if an
installer has no hands-on experience working with the various tools and materials
involved, or have never altered the interior of a car.

INSERT Tip: If a component cannot be self-installed, it is far better to pay the cost of
professional installation than to risk possible damage to the car or even injury to the self.

INSERT Tip: Do-it-yourself does not mean you can’t use a friend. A friend is a second
brain, an extra hand, and more fun.

Do-it-yourself mounting kits, wiring harnesses, connectors and other materials, tools and
accessories are available for most cars. Some cars require no mounting kits, special
speaker connectors, or drastic aleration to the interior when replacing OEM components
with 3rd party components. However, sound systems like those found in national car
audio competitions are highly specialized and go beyond the scope of OEM support.

In cases where there is no OEM support or “universal” kits won’t work, an understanding
of a dizzying array of wire, connectors, tools, and in many cases, soldering, is required.

Professional Installation



Installing or Replacing a Head Unit
(Note: These are general instructions only)
                                                                                          49



INSERT Tip: Always check the spec sheets (specifications) or list of "Key Features" for
any component before installation. Unit wiring schemes, for instance, might differ from
a car’s wiring scheme.

INSERT Tip: For specific car make and model instructions on removing OEM head
units, see the vehicle-specific Crutchfield MasterSheet or the In-Dash Receiver
Installation Guide at the Crutchfield website.

INSERT Tip: A car’s electronic system can be complex, especially in newer cars where
nearly everything is electrical combined with the use of small computers. Short
circuiting the wrong connection can damage the car’s electrical system and be expensive
to repair.

Tools generally used to install a head unit include wire strippers, pliers, screwdriver, wire
crimper and wire nuts, a Volt-OhmMeter, and electrical tape. A Volt-OhmMeter is safer
to use than a 12-volt light tester.

Remove the old receiver.

Head units have a ground wire, a 12-volt electrical power wire, and 4-8 speaker wires.
Sometimes there are connections for line inputs/outputs for other devices like a CD
changer or power amplifier. Use a wiring schematic if one is available and label each
wire (a marker or taped piece of paper).

Connect the positive [+] wire from each speaker to the positive terminal or wire end and
negative wire [-] from each speaker to the negative terminal. Speakers are ground at the
car chassis. If connecting wire to wire, strip each end of insulation leaving exposed
enough wire to twist together with the new unit’s wires. After twisting the wires
together, secure the connection with a wire nut and tape over with electrical tape.

Make sure the ground wire is connected to a metal frame or screw nearby where the
united is mounted in the dash. Wood, plastic or other non-metallic materials do not
conduct electricity. Make sure the connection—as with all connections—is secure.

Make sure the ignition is off and pull the 12-volt constant voltage wire from the cigarette
lighter. Use the Volt-OhmMeter to test for the correct wire. Connect the constant voltage
lead from the head unit to the 12-volt constant. Connecting the constant lead provides
power to the unit’s clock and memory features. Turn on the ignition and select the wire
from under the dash. Connect the "turn on lead" from the radio to the ignition.

INSERT Tip: An excellent source for specific car schematics and repairs is Chilton’s
repair manuals (available in most libraries).

Check for other leads from the unit, used to power an amp or antenna. Some units
provide line in and line out for RCA plugs. There may also be a plug for the antenna. If
                                                                                           50


nothing else is being connected, cut off any remaining exposed wire and then wrap with
electrical tape or wire end caps to the ends don’t touch any metal surface and short out.

Connect the main power cable after all other connections are made.

Most units have metal braces and/or brackets to mount in the dash. In some cases,
universal mounting kits will work.



Preface notes:
There are far too many factory and brand name models of head units, amplifiers,
equalizers, speakers and other components and accessories to be covered in one book
(thank the cyber-Gods for the Internet). However, each component's chapter lists major
manufacturers. In-dash head units and portable mp3 players are listed in greater detail.
Going to the manufacturers website will provide a detailed list of audio component
makes and models with feature details, pricing, photos and more. Crutchfield.com is
perhaps the most authoritative and comprehensive website covering the full range of
audio components for the car (and for the boat and home).


When installing a new receiver in your car, your first step will be to remove the old
receiver. Pay close attention to the steps involved, for the process for installing your new
receiver will be the same, but in reverse.

Removing the factory radio
For detailed information on how to remove the factory stereo in a specific vehicle, refer
to your Crutchfield MasterSheet™ instructions, if available. They will walk you through
the process step-by-step. Otherwise, you may use the general guidelines below.

Before you begin, start by setting the parking brake and removing the negative cable
from the car battery to prevent accidently short circuiting something.

Your factory radio will be mounted in one of two ways:
secured in a metal mounting sleeve by spring clips
bolted to the dash with brackets


DIN tools are used to remove the factory radio from a 2000 Ford Expedition.

Spring clip mounting
If the receiver is held in by spring clips, you'll need a pair of DIN tools. Insert the DIN
tools into the holes on eitter side of the unit until a click is heard. The tools serve to
release the spring clips and also hook onto the sides of the radio so that you can pull it out
easily. Spread the tools apart slightly then pull the radio out of the dash.
                                                                                            51


Bolted in place
Sometimes, accessing the radio requires the removal of one or more trimpanels from the
dash. You may have to (carefully) pry the plastic trim away from the dash (which is often
secured by hidden pressure clips), or locate and remove bolts to disassemble other pieces
of panel. Once you have gained access to the factory radio, removal should be obvious.
The radio will almost always be secured by four screws, sometimes bolted directly to the
front of the dash, other times secured to side brackets. Remove the screws and pull the
radio from the dash.


Four philips screws secure the factory receiver in a 1992-94 Geo Metro.
Four bolts and a pair of side brackets attach the receiver to the dasgh in a 1998 Toyota
Sienna.

American cars built before the early 1980s often came with a "shaft-style" receiver,
which secured to the dash via nuts and washers to the right and left knobs. A shaft-style
receiver must be installed from behind the dash. Getting it into position is the tricky part,
since your vehicle's wiring, heater controls, and ductwork may be in the way.

Unplugging the factory radio

Factory wiring harnesses.
If your vehicle has (or once had) a factory radio, or if it was pre-wired with a "radio prep"
package, there should be at least one plastic wiring harness behind the radio opening.
This plug(s) connects the radio to your vehicle's electrical system, and also makes the
speaker connections. You will need to unplug the factory radio from the wiring
harnesses, and unplug the antenna to complete the removal process.

Prepping the new receiver
If Crutchfield carries a custom wiring harness for your vehicle, you can use it to connect
your new receiver to your vehicle's factory wiring harnesses. This will ensure that
everything works seamlessly, just like the factory receiver did.


A custom wiring harness makes installing a new receiver much easier.

If a harness is not available for your vehicle or if the factory stereo plug was cut off,
you'll need to identify each of the stereo wires and connect them to the corresponding
wires of your new receiver. If you purchased your new receiver from Crutchfield, our
Tech Department may be able to tell you the colors and functions of your car's stereo
wires.

Crimping and Soldering
Decide whether you want to crimp or solder the wires together. Crimping is faster and
easier. If you crimp the wires together, be sure to use the correct size crimp connector —
typical in-dash receiver wires are 18-gauge, but a few use heavier gauge power and
                                                                                          52


ground wires. There are several types of crimp connectors, including bullet connectors,
butt connectors, or crimp caps (pictured below).

Soldering creates a permanent, professional connection that ensures maximum current
transfer. We strongly recommend that you use heat-shrink tubing and a heat gun to
insulate the soldered connection. Avoid taping the wires together — the tape will dry out
and fall off, exposing the wires and making it only a matter of time before something
shorts out.




Power
Usually, it is best to make all of the new stereo's wiring connections via the wiring
harness, but if you have to make a direct power connection, you'll need to know the
difference between "switched" and "constant" power.

A switched power source is only on when the ignition is keyed — connect your new
receiver's main (switched) power lead to a switched power source, so that the receiver
will turn off when you turn off the car, and not drain your vehicle's battery.

A constant power source is always on — connect your new receiver's memory lead to a
constant power source, so that you don't lose your radio preset, sound shaping, and clock
settings every time you turn off the vehicle.

A few high-powered receivers require you to make a direct constant power connection at
the positive terminal of your vehicle's battery. This requires a heavier gauge power wire,
an in-line fuse (usually included), and a ring terminal to connect the power wire to the
battery clamp. You will have to route the power wire through the vehicle firewall and
into the engine compartment in order to make the connection at the battery.

Ground
A good ground connection is vital for proper receiver performance. If you are not using a
custom wiring harness, look for a bolt, screw, or wire that contacts the bare metal of your
vehicle's chassis. Loosen the bolt, slip the ground wire underneath (this is almost always
a black wire), then tighten the bolt. If your ground wire doesn't contact bare metal, your
receiver won't operate. A loose or weak ground connection can result in signal noise
interfering with your music.

In-dash video wiring
If your new receiver has a video monitor built in, you will also need to connect a wire to
your emergency brake circuit's ground wire. This wire acts as a switch to turn on the
video monitor when the parking break is engaged. Follow the instructions included with
your in-dash monitor to locate the emergency brake ground wire.
                                                                                             53


Installing the new receiver




You might need to use a backstrap to support the rear of your new receiver.
If the original stereo was bolted into the dash, you might need to remove the mounting
brackets from the sides of it and attach them to the sides of your new receiver. More
likely, you will need a mounting kit (which may include a trim ring, a dash insert,
brackets, a faceplate, and/or a metal mounting sleeve) to install the receiver (Figure 1).

If a mounting kit is required, install it first. Then slide the new receiver's metal mounting
sleeve (if included) into the kit. Secure the metal sleeve by using a screwdriver to bend
the sleeve's metal tabs into place (Figure 2).

Once the dash opening is ready for the new receiver, hold the receiver near the opening.
Connect the receiver wiring adapter to the vehicle's wiring harness and plug in the
antenna cable.

Slide the receiver into the dash opening, but don't fasten it down just yet. First, test the
receiver to make sure everything is working properly. It's easier to fix a problem while
everything is still exposed. Turn on the power and try each source (AM, FM, and CD).
Then adjust the balance and fader settings to check that each speaker is working. Once
you're sure the receiver is wired and working properly, finish securing it in the dash and
reinstall any pieces of dash trimpanel that you removed.

Installing a backstrap

Dealing with "Premium" factory systems

This adapter allows you to install an aftermarket receiver in a 2003-up Honda Accord's
dash panel, while maintaining all heating, ventilation, and air conditioning controls.
If your vehicle has a Premium sound system or an integrated receiver/climate control
panel, you will probably need a special "OEM integration" adapter in order to install a
new receiver. The appropriate adapter can be purchased from crutchfield.com. An adapter
allows you to use a new receiver with your existing speaker system.

Evaluation
By now you should have some idea of what is involved in replacing your factory receiver
with a new, better aftermarket receiver. The next step is to see if Crutchfield has a
MasterSheet™ for your vehicle. That's a set of installation instructions custom designed
for your specific vehicle. It will describe every step of the process and tell you where to
find every screw you need to remove for the installation. A MasterSheet™ takes all the
guesswork out of the installation.
                                                                                          54


Even without a Crutchfield MasterSheet™, most people can install an in-dash receiver
without much trouble, using just the tips in this article. This in turn leads to a savings
($50 is common, and often more) in installation fees. But if you would rather not tackle
the task, there are competent and highly trained professional stereo installers in every
town where you'd find teenagers and cars.

As with any car audio/video installation, your first step is to disconnect the negative
terminal of your car battery to prevent short circuits — check your MasterSheet™ for
specific directions on how to disconnect your vehicle's battery.


CD Changer Installation
Some vehicles are pre-wired for factory-compatible CD changers, providing a relatively
practical and painless installation. However, universal add-on CD changers work with
virtually any head unit.

Common locations for multi-disc changers are the trunk, under the front passenger seat,
and glove boxes, if they’re large enough. Glove boxes are frequently large enough for
MiniDisc or an MP3 unit.

Disconnect the negative battery terminal. The battery is always disconnected before
installing any new electrical component. The mounting area must be firm enough to
support the changer so it won’t be knocked loose by car reverberations. Open exposure
runs the risk of theft or damage by sunlight. A trunk location works but changing the
magazine is a hassle and running cables from the trunk to the dash can be a complex
process (like amplifiers and subwoofers).

A trunk location means running signal wires across one side of the car, removing the
head unit, and making the connection in the back of the unit. If an amplifier is installed
as well, it’s best to run the cables run on the opposite side of the amp’s 12-volt power
cable to avoid electrical or car noise. Depending on make and model, the backseat might
have to be removed to find a place to run wire from the trunk. Trim panels, door sills,
and carpeting might have to be removed as well to run the cable along the car’s
floorboard.

INSERT Tip: Running power and signal wire from the same unit or different units along
the same side of the car runs the risk of noise interference.

Add-on (FM-style) CD changers require two 12-volt power wires to hook up. One goes
to a constant source of power and the other goes to a switched 12-volt source. There is
also a ground wire. The signal cable runs from the changer to the FM modulator (some
changers have built in FM modulators). Another cable runs from the FM modulator to
the antenna input of the head unit. The antenna is plugged into the FM modulator.

INSERT Tip: Even when connecting a same-brand peripheral to a head unit, it’s
important to verify compatibility since unit features change over time. The same applies
                                                                                          55


to factory head units with changer controls connected to factory-compatible CD changers.
Adapter cables and kits are available for most cars, but these too can change over time.
Factory units with changer controls can be connected to aftermarket changers via vehicle-
specific adapters (again, verify compatibility).

Mounting tips: Trunk
If you plan to suspend a CD changer or hideaway box from the bottom of the rear deck,
first make sure the component won't interfere with the torsion bar of the trunk lid.
Observe how it moves as you close the lid before you settle on the exact mounting spot.

Many changers come with mounting brackets that you secure to the vehicle with bolts or
screws. Get a helper to attach the nuts to the mounting bolts while you hold the changer
in place and run the bolts through the brackets and the holes you drilled in the deck. If
your changer mounts with self-tapping screws instead, you might be able to handle this
step by yourself.

Mounting tips: Under a seat
When mounting a peripheral source component under a seat, be certain that the
component is well-ventilated and that it will not interfere with any seat adjustment
controls. You may find it necessary to remove the seat to access the floorboard. If you
use self-tapping screws or need to drill pilot holes to secure the component to the vehicle,
make sure you know what you're drilling into. Check that the gas tank, brake line, and
other parts are not on the other side of where you are drilling/screwing. Most components
also include the option of using Velcro strips.

Cable routing
If you're mounting your peripheral source in the trunk, you'll probably want to run the
signal/controller cable(s) from the in-dash receiver down one side of your car. (You'll
have to remove your receiver from the dash to access the changer connection.) If you also
have an amplifier in the trunk, run the source's cables on the side opposite the amp's 12-
volt power cable. You'll be less likely to introduce engine noise into your system.

In most cars, you'll be able to find a hole or crevice to slide the cable from the trunk into
the passenger compartment. You may have to remove the rear seat to find it. To hide the
cable beneath your carpeting, you will have to remove the door sill. As you pass the cable
along the floorboard, make sure it doesn't sit too close to a seat rail, where it could be
pinched or damaged when the seat is adjusted.

If you're running the cable up the driver's side, you'll want to make sure it doesn't end up
in the way of the pedals, the steering column, or hood latch. Tie it firmly in place with
wire ties and coil up any excess cable, so it won't fall on your feet as you drive.
Remember to test the new source thoroughly before you fully reinstall your in-dash
receiver.

Panel Removal
                                                                                           56


The instructions below address, in general, what panels may need to be removed and how
they typically come off. Often, panels can be pried up at edges. Screws and retaining
clips might also be present that will require removal (Figure 1). To prevent damage,
always use care when removing panels.

Door Scuff Plate removal
The plates are usually removed by prying up the edges to release clips. Some vehicles
will have screws present which will need to be removed (Figure 2).

Seat Belt removal
A seat belt may be located on the panel that needs to be removed. Most seat belt anchor
covers pry off. The seat belt anchor is secured with a large nut or bolt (Figure 3).

Pillar Trimpanel removal
Remove seat belt if present. Remove screw covers, screws and plastic retaining clips, if
present. Pry up edges of panel to remove (Figures 4 & 5).

Kickpanel removal
Look for screws and pry-out retaining clips to remove. Pry out edges of panel to release
and remove (Figure 6).

Routing wire behind dash
Route wire behind dash and secure with plastic wire ties. Be sure that wire does not
interfere with any moving parts to ensure safe operation of vehicle.

Routing wire for components and power connections
Determine desired locations for each component. Use the most direct route for wires.
Remove panels necessary to route and conceal wires. Test system before reinstalling
panels.


Amplifier Installation
An amp can be securely installed with just a few screws. But since amps can be sensitive
to electrical and motor noise and because interference from the amp may affect your
radio reception, try to mount it at least 3 feet away from the receiver. Good locations
include:

Good locations include:
Under a seat

Pros: Closer to the receiver, so you can use shorter patch cables and signal cables, which
are less prone to noise and signal degradation. Closer to the front speakers, so running
wire to them will be easier. No cargo space sacrificed.
                                                                                          57


Cons: You may have to remove the seat to do the installation. Larger amps might not fit.
You must elevate the amp to avoid contact with water from rain or snow brought in on
passengers' shoes.

On the firewall (passenger side)

Pros: Short wires and patch cords required. You won't have to remove a seat or climb into
the trunk.

Cons: Only very small amps fit here. Closer to some common noise sources.

In the trunk or hatch area
Pros: Lots of room for large amps. Near the rear speakers or sub enclosure.

Cons: You sacrifice some cargo space. Longer wires and patch cords required.
Note: When working inside the trunk, tape over the latch, so you won't become trapped
inside accidentally.

Keeping your amp cool
Something else to consider when choosing a mounting spot: Amplifiers produce heat, and
the heat must be dissipated efficiently. The amp's cooling fins absorb heat and radiate it
into the surrounding air. For the cooling fins to operate efficiently, they need a few inches
of air space around them. When mounting the amp on a side wall, try to position it so that
the slots in the cooling fins are vertical.

Amps should not be mounted on the bottom of a rear deck with the fins facing down
because the heat will radiate back up into the amp. Leave yourself enough room on either
side of the amp to make all the wire connections and adjust the controls. If you have a
subwoofer box in your vehicle, you can mount the amp on the outside of the box.

If you are mounting the amp to the vehicle's floor, check beneath the car to be sure your
screws won’t puncture a brake or gas line.

Amplifier Wiring Kits
Amplifier wiring kits contain power and ground cable, a thin piece of wire for the turn-on
lead, a fuse or circuit breaker, and all the connectors you need. The main power lead
should be thick, since it draws power directly from the positive battery terminal. An in-
line fuse or circuit breaker installed near the battery is a must. Without one, an accidental
short circuit could pose a fire hazard and damage your amp.

Select the wire (10-, 8-, 4-, 2-, or 1/0-gauge) that's appropriate for your installation,
depending on the length of wire you want to use, the power of your amplifiers, and how
you plan to use them. For more information, check our cable gauge selection chart. Make
sure that the fuse rating of your amplifier does not exceed the rating of the fuse that's
included with your wiring kit — if so, you'll need to buy a larger fuse.
                                                                                              58


No preamp outputs on your receiver?
Most aftermarket receivers provide preamp output from RCA jacks. In this case, an RCA
patch cable carries the signal from the receiver to the amp. If your receiver does not have
preamp outputs, many amplifiers feature speaker-level inputs, which have built-in
converters which step the speaker-level signal down to a preamp-level signal acceptable
to the amp.

You can access the speaker-level signal by stripping a small section of your vehicle's
right and left speaker wires, and splicing in wires that lead to your amp (similar to
splicing into your receiver's turn on wire). Note: Tapping into speaker wires in this
manner does not affect the performance of your speakers.

If your amp doesn't have speaker-level inputs, an effective and inexpensive line output
converter will help you step the speaker-level signal down to preamp level. Then run an
RCA patch cord from the converter to the amplifier. Make sure the patch cords supplying
the musical signal to the amplifier are kept well away from potential sources of noise,
such as brake light wires or rear window defroster wires.

Installing an amplifier calls for a little more skill and creativity than installing a receiver
or a pair of speakers in the factory locations. But when the installation is done, you'll
notice that the extra power will give you more volume and much cleaner, more dynamic
sound, even at low listening levels. If you love music, you'll be knocked out by the
difference!

Wiring
1. Disconnect the negative terminal from your battery — this allows you to run power
cable through the vehicle without risking a dangerous short circuit. Remove the red
power wire from your amp wiring kit (usually 16-20 feet in length). Locate a hole on the
firewall of your vehicle; most cars will have a predrilled hole you can use. If not, you'll
have to find a good place to drill one — take care not to drill through a gas line or
electrical wiring!

For example, in a Ford with an automatic transmission, there's a plate that covers the
clutch pedal opening — you can drill through this plate without hitting anything.
Once you've found or drilled a suitable hole, run the power wire through the hole into the
engine compartment. (Install a rubber grommet in the hole to prevent damage to the
power cable.)

2. Find a good spot close to your battery to place your fuse holder (included in the kit) —
you'll want the section of power line between the fuse and the battery as short as possible
(less than 6" is best). Cut a short piece off the end of the power wire (to cover the
distance from the battery to the fuse holder location), and strip the insulation off both
ends with a wire stripper.

Crimp the terminal ring (included in the kit) on one end of the short piece of wire, and
crimp the fuse holder to the other end. Strip the insulation off the end of the red power
                                                                                            59


wire that leads into the passenger compartment, and connect it to the other end of the fuse
holder. (Note: in some wiring kits, the power wire may already have an inline fuse holder
installed.)

3. Connect the ring terminal to the battery, and anchor the fuseholder to a suitable spot
with a self-tapping screw (smaller fuseholders may not have to be anchored). Thread the
wire loom (included with some kits) over the red power cable until it reaches the firewall
and cut to fit.

Thread another piece over the short power wire running from the fuse holder to the
battery.

4. Remove the radio from the dash to access the turn on wire (usually a blue wire). Strip
the insulation off a small section of this wire coming from the radio (as pictured), wrap
the blue turn on lead (included with the kit) around it, and solder it.

Wrap the exposed area with electrical tape to guard against a short. Using wire ties
(included with the kit) to secure the wire, route the blue turn on lead behind your dash all
the way over to the place where the red power wire comes through the firewall.

5. Connect the RCA patch cables (included with most kits) to your radio's RCA preamp
outputs (tape them together so they don't come apart), and route the cable (again, using
the wire ties) to the OPPOSITE SIDE of the vehicle from the power cable and blue turn
on lead. It's important to separate the patch cables from the power wires to avoid
potential noise problems. Partially reinstall the radio in the dash (not all the way, in case
you have to fix a problem later).

6. Remove the door sill trim panel (it pops off on most vehicles, but check for screws
before you try) on both sides of the car. Route the red power wire and blue turn on lead
under the carpet down one side of the vehicle, the RCA patch cables down the other side.
Replace the trim panels, and route the wiring along the rear side panels (there's usually a
good place to tuck it away), around the sides of the rear seat, and into the trunk (or
wherever you've decided to mount the amp).

7. Remove a bolt near the planned amp location. Crimp a ring terminal (included with
kit) to the short piece of black ground cable (also in the kit), and then bolt the terminal
tightly to the vehicle’s metal chassis. Scrape away any paint and clean the bolt location
thoroughly (improper grounding is the #1 cause of noise problems). If you can't find a
convenient ground screw or bolt, drill a hole for one — be careful not to drill into the gas
tank or a gas or brake line.

8. Mark off the amp's location on the seat back (or wherever it's going), also noting the
location of the power connections, speaker outputs, and preamp inputs. Make slits in seat
back fabric, and run the power, speaker, and RCA wiring under the material to the
appropriate slits. A wiring snake (available at hardware and auto parts stores) is handy
here — Insert the snake through the slit and reach to the bottom of the seat, grab hold of
                                                                                           60


the wiring with the snake's grips, and pull it through. (No wiring snake? A coat hanger
will do in a pinch.)

9. Install grommets and terminals (included in wiring kit) at the ends of the power,
ground, and turn on leads, and connect to the amplifier. Hook up speaker wire and RCA
patch cables to the amp. Turn on the radio, and the amp should fire up. Start your car, rev
your engine, and listen for any engine whine coming through the speakers. If there are no
noise problems, reinstall the radio and mount the amplifier in place with dry wall screws
(type of screw may vary according to the mounting location).

 10. Connect speaker wires to the subwoofer box (or speakers). Adjust the gain controls
on the amplifier according to the instructions in your manual. If you're hooking up a
subwoofer, turn up the radio to a healthy volume level, and adjust the gain controls so the
bass is well-matched to the full-range speakers. A test disc (or bass-heavy CD) is helpful
for making final adjustments.

11. Put the seat back up, clean up the mess, and rock out! A Dynamat license plate kit
will cure any case of rattling license plate caused by massive bass output!

The installation of your amplifier will depend on the make and body style of your
vehicle, as well as the equipment purchased.

A note about wiring: In addition to the tools listed above, your amp installation will
require power and ground wiring, plus RCA cables, terminals, and a remote turn-on lead.
The easiest way to get all of these items is in an amplifier wiring kit, available at
crutchfield.com.

Planning ahead:
Choosing your location according to these guidelines will help your installation go
smoothly:

The amp should be at least three feet from the receiver to avoid noise radiated from the
vehicle's electrical system. The amp can also interfere with the receiver's AM/FM
reception.

An amp produces some heat during operation, which its heatsink absorbs and radiates, so
it needs a few inches of air space to stay as cool as possible. When mounting an amp on
a side wall, make sure the fins on the heatsink are vertical. Never mount an amp upside
down, as dissipated heat will radiate back into the amp.

There must be enough room on either side to make the wiring connections and adjust the
controls (gain, crossover, bass boost, etc.).

INSERT Tip: Follow the manufacturer's recommendations for mounting the amp and
make sure it's secure. An amp that isn't secure could break loose in an accident and injure
a passenger as it flies through the vehicle.
                                                                                          61



Making the power connections
1. Set the parking brake and disconnect the negative terminal from your battery to
prevent any electrical short.

Route the red wire from your amp wiring kit through a hole in your vehicle's firewall.

2. Remove the red power wire from your amp wiring kit (usually 16-20 feet in length).
Locate a hole on the firewall; most cars have a predrilled one you can use. If not, you'll
have to find a good place to drill one. If you have problems, contact Crutchfield technical
support at the phone number listed on your invoice. Once you've found or drilled a
suitable hole, run the power wire through the hole into the engine compartment.

3. The red power wire from your amp wiring kit may have a fuse holder installed. If so,
go to step 4. If not, find a good spot close to your battery to place your fuse-holder
(included in the kit) — less than 6" from the battery is best. Cut a short piece off the end
of the power wire (to cover the distance from the battery to the fuse holder location), and
strip the insulation off both ends with a wire stripper.

Crimp the terminal ring (included in the kit) onto one end of the short piece of wire, and
crimp the fuse holder onto the other end. Strip the insulation off the end of the red power
wire that leads into the passenger compartment, and connect it to the other end of the fuse
holder.

Fuse installed on power wire, and secured in engine compartment.

4. Attach the power cable to the positive battery terminal (not directly to the battery post
itself). For top-mounted battery posts, the most common way to do this is to crimp a ring
terminal onto the end of the power cable (most cables in wiring kits come with it already
attached). Remove the battery terminal's nut, slip the power cable's ring over the bolt that
secures the battery terminal to the battery post, and replace the nut. For GM vehicles with
a side-mount post, we offer an adapter that works nicely.

Thread the wire loom (included with some kits) over the red power cable until it reaches
the firewall and cut to fit. Thread another piece over the short power wire running from
the fuse holder to the battery.

Anchor the fuse holder to a suitable spot with a self-tapping screw (see photo above).

5. Remove the radio from the dash to access the turn-on wire (usually a blue wire). The
turn-on wire will "tell" your amplifier to turn on whenever the receiver is powered up
(usually, whenever the vehicle is turned on).


Locate the remote turn-on lead behind your radio (usually a blue wire), and connect the
turn-on lead from your amplifier wiring kit to it.
                                                                                           62



Strip the insulation off a small section of this wire coming from the radio, wrap the blue
turn on lead (included with the amp wiring kit) around it, and solder. Or, use crimp
connectors and a crimp tool to connect the blue turn on lead to the wire coming from the
radio. Wrap the solder or crimp connection with electrical tape (or use a heat gun to apply
heat shrink tubing) to guard against a short. Using wire ties (included with the kit) to
secure the wire, route the blue turn on lead behind your dash all the way over to the place
where the red power wire comes through the firewall.

Making the signal connections
6. If your in-dash radio has preamp (RCA) outputs, connect the RCA patch cables
(included with most kits) to these outputs, taping them together so they won't come apart.
Route the patch cables (again, using wire ties) to the OPPOSITE side of the vehicle from
the power cable and blue turn on lead. It's important to separate the patch cables from the
power wires to avoid potential noise problems. Now you can partially re-install the radio
in the dash (don't push it all the way in, in case you need to fix a problem later).

Wire routing
All system wiring should be concealed for safety, and to give your installation a nice,
finished look. Wires should be secured so that they do not interfere with safe vehicle
operation. Depending on the vehicle and the location you choose for your amplifier, the
wiring for your system may need to be run under the dash, door scuff plate, pillar
trimpanel, or kickpanel. The instructions below address, in general, what panels may
need to be removed and how they typically come off. Often, panels can be pried up at
edges.
Screws and retaining clips might also be present that will require removal. To prevent
damage, always use care when removing panels — a panel tool is helpful.

Door scuff plate removal
The plates are usually removed by prying up the edges to release clips. Some vehicles
will have screws present which will need to be removed (Figure 2).

Seat belt removal
A seat belt may be located on a panel that needs to be removed. Most seat belt anchor
covers pry off. The seat belt anchor is secured with a large nut or bolt (Figure 3).

Pillar Trimpanel removal
Remove seat belt if present. Remove screw covers, screws, and plastic retaining clips if
present.

Pry up edges of panel to remove

Removal of pillar trimpanel

Kickpanel removal
                                                                                            63


Look for screws and pry-out retaining clips to remove. Pry out edges of panel to release
and remove

Routing wire behind dash
Route wire behind dash and secure with plastic wire ties. Be sure that wire doesn't
interfere with any moving parts to ensure safe operation of vehicle.

Routing wires for components and power connections
Determine desired locations for each component. Use the most direct route for wires.
Remove panels necessary to route and conceal wires. Test system before re-installing
panels.

Amplifier mounting and connections
7. After routing the power and signal cables to your amplifier, using the techniques
described on page 3, you're ready to mount and hook up the amplifier. First, remove a
bolt near the planned amp location. Crimp a ring terminal (included with the kit) to the
short piece of black ground cable (also in the kit). Scrape away any paint and clean the
bolt location thoroughly (improper grounding is the #1 cause of noise problems), and
then bolt the terminal tightly to the vehicle’s metal chassis. If you can't find a convenient
ground screw or bolt, drill a hole for one — be careful not to drill into the gas tank or a
gas or brake line).

Bolt the ground terminal tightly to the vehicle's metal chassis.

8. Mark off the amp's location on the floor or seat back (or your chosen location), also
noting the location of the power connections, speaker outputs, and preamp inputs. Make
slits in seat back fabric (or carpet, if the amp is to be mounted on the vehicle's floor), and
run the power, speaker, and RCA wiring under the material to the appropriate slits. Here's
where a wiring snake (available at hardware or auto parts stores) comes in handy. Insert
the snake through the slit, grab hold of the wiring with the snake's grips, and pull it
through.

A wiring snake can come in handy for pulling wires to the amp mounting location.

9. Install grommets and terminals (included in wiring kit) at the ends of the power,
ground, and turn-on leads, and connect them to the amplifier. Hook up speaker wire and
RCA patch cables to the amp. Reconnect your car's negative battery cable, turn on the
radio, and the amp should fire up. Start your car, rev the engine, and listen for any engine
whine coming through the speakers.
If there are no noise problems, re-install the radio and mount the amplifier in place using
Self-tapping screws. See our Noise Suppression Guide for tips on diagnosing and treating
noise problems.

RCA cables routed through slits in the vehicle's carpet, and connected to the amplifier's
signal inputs.
                                                                                             64


10. Connect speaker wires to your subwoofer box (or speakers). Then, to maximize clean
signal strength from your amp, you need to adjust the gain or input sensitivity settings.
Here's how:

Set the input sensitivity controls of your amplifier to their minimum level (counter
clockwise). Put in a CD and turn the receiver's volume control up (you might have to
raise the amp's gain just a bit to hear the music). When you hear distortion, stop. Turn the
volume down until it disappears. As much signal as possible is passing from the receiver
to the amp. This maximizes the signal-to-noise ratio, and leaves your system less prone to
engine noise problems. Keeps the volume setting here. Now turn the gain controls on the
amplifier up until it's as loud as you'll play it. If you hear distortion, slightly decrease the
gain settings. Now you've optimized the amp's output with the receiver's volume set near
maximum. You can turn the volume almost all the way up and not damage your speakers
or amplify distortion. If you’re hooking up a subwoofer, a test disc (or bass-heavy CD) is
helpful for making final adjustments.

Multi-amp installations
Powering multiple amplifiers:
If you're installing more than one amplifier, run a single heavy-gauge power cable from
your battery to a distribution block, and then connect lighter-gauge cable from the block
to each amp. This arrangement minimizes potential noise problems and keeps your
installation looking neat. Make sure you use power cable that's thick enough to
accommodate any amps that you might add in the future.

Grounding multiple components:
If you're installing several components, use a distribution block to organize the various
ground cables into one larger cable. If that's not an option, try to ground each one
separately, with about a half-inch of space between each of the grounding points.

If you'd rather use a single bolt, place the ground for the component that draws the most
current (your most powerful amp) closest to the car body. Put the ground for the
component that draws the least current on top.

Turning on multiple components: If you have multiple components in your system, you
may need a relay to protect your receiver. That's because the receiver's power antenna
lead can only supply a limited amount of current. If the components in your stereo system
ask for more current than the receiver can supply, you can burn out that circuit in your
receiver. A relay connected to the power antenna lead draws a small amount of current
from the receiver, but supplies enough current to turn on all your other components
simultaneously.

Power demands of a multi-amp system: Some cars' systems are designed for additional
current loads (trailer towing packages, for example), but most of them are not. Luckily,
most manufacturers design their cars' electrical systems with a reserve capacity that is
well-suited to supplying power for a sound system. Look at the tag that is riveted or
                                                                                           65


screwed to the side of the alternator. This tag tells you how much current (expressed in
amperes or amps, for short) the alternator is capable of producing.

Your car's alternator ampere rating determines how powerful an amplifier you can install.
Multiply the ampere rating by 40% and you'll get a rough idea of how much reserve
current capacity your car's system has. Next, you'll need to calculate the approximate
current draw of the amplifier you're considering installing.

To calculate the current draw of an amplifier, multiply the number of channels by the
RMS watts per channel (a 2 channel amp rated at 300 watts RMS per channel would be
600 watts). Double it to account for amplifier inefficiency (600 watts X 2 = 1200 watts),
then divide by the average output Voltage of an alternator, 13.8 volts (1200 divided by
13.8 = 87 amps). Since the average music signal requires about 1/3rd of the average
power in a test tone, divide by 3 (87 amps divided by 3 = 29 amps). The result is the
amplifier's approximate average current draw.

A quick way to ballpark an amplifier's current draw is to divide the total fuse value of the
amp by two. For amplifiers with multiple fuses, the rating of all fuses provided with the
amp must be added together. This will likely produce a significantly higher estimate than
using the proper formula. Although inaccurate, this will err on the side of safety.

Finally, compare the amplifier's approximate current draw to your vehicle's reserve
current capacity to determine if the electrical system can support the amplifier.

If all those numbers are a bit much, here's a simpler way to think about it: an alternator
capable of producing 65 amperes is usually adequate for systems up to 270 X 2 watts
RMS. A compact car with a 35-amp alternator can accommodate around 150 X 2 watts of
power, while a Sport Utility with a 145-amp alternator can handle a 600 X 2 watt system.

If you want more power than your alternator can service, you will have to consider
having your alternator rebuilt for higher output — or invest in a high-output aftermarket
alternator. Installing a second battery won't help — that only allows you to play your
stereo for long periods with the engine off. But, remember that any system playing at
one-third volume is drawing considerably less current than the same system at three-
quarter volume, and may not need a charging system upgrade if the volume levels are
kept reasonable.

If your system needs more current than the alternator can supply, it starts to grab current
from the battery — not a good thing for your car or your music! Here are a couple of
warning signs to look for: your headlights dim in time to the music when you crank it up
loud at night; your bass sounds great when you first turn it on, but gets mushy and less
powerful within a minute or so. One easy, effective solution is installing a capacitor.
Heavy-duty capacitors connect to the power cable (just before it reaches your amplifier)
and act as a buffer zone between your amp and your car's electrical system. They store up
a reservoir of power which can supply the amplifier’s peak demands (like a kick drum
beat) without having to pull current from the battery.
                                                                                           66



Amplifiers: How to Suppress Noise
Electrically speaking, your car is a pretty active place. Every piece of electronic
equipment in your car, such as power windows, your windshield wipers, and the
alternator, generates its own small electrical field. These fields can be conducted through
the metal that makes up your car’s body and chassis. They're not really a problem until
they sneak into the audio components of your stereo system and become noise.

You know what noise in a stereo system sounds like: it's that high-pitched whine that
often gets louder as the car goes faster. It's generally due to electrical radiation being
conducted by the audio cables of the vehicle's stereo. The threat of noise increases when
you add an external amplifier, as the presence of more power- and signal-carrying cables
translates into more potential intrusion points for radiated noise. It can be a pretty pesky
problem, easily introduced, but difficult to pinpoint and eliminate.

Fortunately, there are steps you can take when installing a new amplifier to prevent the
introduction of noise.

Grounding
An important factor in preventing the intrusion of noise is to make sure your amp is
solidly grounded. Your amp's ground wire should be fastened securely to a section of
bare metal, and connected tightly to the amp itself.

Isolate your amp
If you have a strong ground, yet noise still seems to be a problem, try mounting your amp
on a board, then installing the board in your vehicle using rubber grommets or feet. This
can help isolate the amp from any electrical noise currents that might be conducted
through your car's metal panels.

Wiring
Never underestimate the importance of well-insulated, high-quality wiring as a weapon
against noise. Cheap wiring tends to fall prey to noise intrusion in such a highly
conductive environment (the cables you use at home won't keep out noise, because
they're designed to function in a place that's not particularly conductive). It's best to use
wiring made specifically to reduce noise (twisted-pair designs, oxygen-free copper
wiring, chemical-proof jacketing, for example); the better the wiring, the less noise you'll
get.

Cable routing
Don't make your amp its own worst enemy! Ironically enough, your amp's power cables
can radiate noise into its signal cables (patch cords and speaker wire). When running the
power and signal cables through your car during installation, you should route them as far
from each other as possible (at least 18 inches apart is ideal).

Diagnosing noise problems
                                                                                            67


Use this diagram to diagnose and cure the most common noise problems associated with
outboard amplifiers. The general idea is to isolate the specific cause of the noise in your
system.

Sometimes, noise can be eliminated just by topping off the fluid with distilled water!

Tools
What tools should I have in order to do a good installation?

Multiple size screwdrivers, both flathead and Phillips.
Phillips screws are most common; be sure to have #0, 1, and 2 sizes. Magnetic
screwdrivers are especially useful when trying to get screws into (and out of) tight places.

Soldering Iron
Makes the best connections if done with care. Use 60/40 rosin core electrical solder. The
soldering tool should use power of between 50 to 75 watts for most purposes

.Electrical tape
Use quality tape that has long lasting adhesion at extreme temperatures.

Wire cutters/strippers and crimpers
For stripping insulation easily, use a pair with stripper holes precut for common wire
sizes and a smaller clipper for finer wire.

Angled screwdrivers
Often makes removing dash and rear deck speakers a lot easier, when windows limit
maneuvering space.

Various wrenches, pliers, and socket sets
The specific types and sizes you need will depend on your vehicle.

Multimeter (VOM)
Essential to diagnose and understand installation problems.

Metal drill and saw
You'll need these if you need to modify your vehicle for new
speaker cutouts or to accommodate a new head unit.

Hot glue gun
Good for installing carpeting or putting door panel trim back in place after modifications.

Razor knife
Helps for cutting carpet and keeping cut out holes neat on door panels or interior walls,
especially when installing speakers.

Hammer
                                                                                            68


For working out frustrations and occasionally delivering needed force to start holes for
screws etc.

Flex tubing & shrink wrap insulation
Good for protecting wire and insulating connections, especially in the engine
compartment.

Extra hardware
Nuts, bolts, screws, crimp-on connectors, wire rolls, tie-downs, etc.

Fuse puller and extra fuses.
In addition to the fuses for your system, check your car's fusebox to find the various sizes
you'll need. Also, while you can use needle-nosed pliers to pull fuses, always disconnect
the battery before doing so.

Wire ties
Keeps the wiring neat and secure.

Small light source
A flashlight or other light source will let you know what surprises linger in the dark
spots.

Tape measure
Keep your wires as long as necessary, and as short as possible.

Amp Installation Procedure

1) Select a location for the amplifier that has good air circulation, such as in the trunk,or
under a seat.

2) Use larger diameter RCA cables to connect the low-level output of the radio to the
low-level input of the amplifier.

3) If the radio does not have a low-level output, you will need to use the high level, or
speaker output. Generally, this is less desirable because of the noticeable increase in
distortion and noise in such an arrangement. If your amp is for bass only, this may be a
less significant problem.

4) Connect the power antenna lead from the back of the radio to the amplifier remote
turn-on (REM) input. When the radio is switched on, 12 volts should appear on the lead,
and start the amplifier when it is connected to the main power leads.

Make certain that the power antenna lead stays on while the receiver is on. On some
radios, power may be switched off from the lead when a CD or tape is played, so the
power antenna will come down. If this is the case with your radio, it may have a separate
lead coming out for the amp turn-on function. Test the lead with a VOM, or test light.
                                                                                           69


When the radio is on, in any function, 12 volts should be present at the amp turn on lead
until the radio power is turned off.

5) Check the owner's manual for the recommended gauge (size) of the power and ground
cables.

6) Connect the negative, or ground power cables before the RCA cables to prevent
damage. If RCA cables are connected first, the amp may try to ground from these cables,
possibly causing damage to other components in the system when it is activated.

Use a fuse on the line at the battery and amplifier. Check your owner's manual for the
proper rating for the fuse. Fuse your amplifier(s) as close to the battery as possible.
Current ratings (in amperes) usually doubles with each amplifier added to a single wire
distribution circuit. For example, if you have one amplifier, using a 35 amp fuse, with
two similar amplifiers, use a 70 amp fuse.

Ensure that power cables do not run next to RCA signal cables. If the cables are too
close, engine noise, which may sound like a high-pitched whine, can get into the system.
If whine is unavoidable, you may wish to use a Noise Filter. In addition to having your
RCA cables mounted away from power cables, make them as short as possible, as signal
strength is lost over distance, and higher frequencies are attenuated.

Connect the main power (+) for the amplifier directly to the battery. Check here for the
proper wire gauge

7) Use the same gauge cable for the amplifier ground (-) as you do for the amplifier
battery (+).

The ground cable should be kept as short as possible. Find a good ground. Clean the area
of rust and paint you select for ground, and bolt the wire to that location. Many of today's
cars have fiberglass bodies. Fiberglass does not make a good ground conductor. Ground
your amp to a solid piece of metal in either the body or frame. If you have noise
infiltration, see our section on Getting rid of Noise.

8) Use 16-12 gauge speaker wire accoding to low or high power, and connect the wire
from the speakers to the amplifier. Make sure that the wire connected to the positive
terminal of the speaker is connected to the positive terminal on the amplifier and the wire
connected to the negative terminal of the speaker is connected to the negative on the
amplifier. If using multiple speakers im a mono circuit, avoid overloading from improper
impedance matching. See Impedance Calculator. When making terminal connections,
strip only as much insulation from the wire as needed to make a good connection. Twist
the wire to prevent any single strand from escaping to touch another conductor.

9) An important indicator of inadequate Power for your system is dimming lights
whenever heavy bass is output. Two possible solutions are a heavier alternator, and/or the
installation of a large power storage/stiffening capacitor. This last item will store large
                                                                                            70


amounts of power until called for by the amplifier. It is generally less expensive than a
replacement alternator, but will not substitute for one if it is needed. See article on
Capacitors.

Installation
Why do I need to add an additional fuse at the battery?
Why fuse at the battery?
How big should the fuse be?
Do I need a separate fuse block too?
What wiring do I need to hook up my amplifier? Does any of it come with the amp?
What size power and ground wires do I need for my amplifier?

How much air space do I need around my amplifier?
How do I hook up multiple amplifiers?

Q: My car audio amplifiers all came with fuses. Why do I need to add an additional fuse
at the battery? And how big a fuse do I need?

A: The answers to most questions about fuses include the word "safety." While most car
audio amplifiers do come with their own fuses, these fuses are designed to protect only
the components themselves. There are a few other bases a safe installation should cover.

Q: Why fuse at the battery?

A: Installing a fuse of the proper amperage on your power cable protects everything
between the fuse and your gear from a short circuit. A short circuit occurs when a
current-bearing wire makes contact with bare metal (like your car chassis). Because your
entire car chassis can be considered "negative" or ground, you can think of a short circuit
as positive touching negative.

You definitely don't want this to happen, but if it does, a properly installed fuse will
prevent a fire or other damage. A fuse does its work by "blowing" and stopping the flow
of current. So, given the alternatives, "blowing a fuse" is a relatively good thing. You can
optimize the protection your fuse provides by installing it closer to the battery — that
increases the length of the protected cable behind it. Twelve to 18 inches from your
battery is the recommended distance.

Q: How big should the fuse be?

A: If you're installing just one amplifier, the fuse at the battery should simply match or
slightly exceed the fuse rating of the amplifier itself. If you're installing two or more
amplifiers, just add their fuse ratings together and install a fuse rated roughly equal to this
sum. Generally, it's better to go slightly higher than lower, but a margin of five amperes
is acceptable.
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Say you have three amplifiers, two with fuse ratings of 20 amps each and one with a fuse
rating of 25 amps. In this case, you can safely go with either a 60 or 70 amp fuse. (Of
course, if your system is powerful enough to demand that you install a heavy duty fuse,
it's important that your power and ground wire be of an appropriately heavy gauge as
well.)

Q: Do I need a separate fuse block too?

A: A safe system will have the right fuses installed at each amplifier and also on the
power cable by the battery. But if you've ever taken a peek at some competition-style car
audio systems, you may have noticed fuses at a third location — in a fuse block by the
components. Sure this hardware looks good, but is it necessary?

Unless your amplifiers are among the few that don't come with fuses installed, the answer
is no. The reason you see these "redundant" fuses is that in the early days of car audio
competition, amplifiers frequently didn't include their own fuses, or if they did, often hid
them behind panels that were hard to get to, especially in the heat of competition.

Today, the use of such fuse blocks is largely a matter of style. But that's OK — looking
cool definitely counts. In the world of car audio, it's a close third, right behind being safe
and sounding great.

Q: What wiring do I need to hook up my amplifier? Does any of it come with the amp?

A: Amplifiers generally do not include the wiring necessary to hook them up. However,
we offer a number of wiring kits that will provide everything you need to send signal and
power to your amp.

You need enough power cable to run from your car battery's positive terminal through the
firewall to the amplifier. Be sure to install an in-line fuse or circuit breaker near the
battery. Without one, an accidental short circuit could pose a fire hazard and damage your
amp (not to mention your car).

You also need another length of the same gauge cable to serve as your ground wire. You
won't need as long a ground wire because your grounding point should be relatively close
to the amplifier.

The last wire you need for powering the amp is a turn-on lead. It doesn't need to be as
thick as the power and ground wires (18 gauge should be fine). It runs from the remote
turn-on lead at the back of your receiver to the remote terminal on the amp. When
connecting these wires, be sure to use crimp-on spade or ring terminals to get the best
signal transfer.

The audio signal travels from the back of your receiver to your amplifier through an RCA
patch cable. Your patch cable should be long enough to reach the amp but not so long
that it has a lot of slack and could become kinked over time.
                                                                                         72



At the other end of the amp, you'll need speaker wire. Generally 14, 16, or 18 gauge wire
should be sufficient. Keep in mind those current flows more easily through thicker wire.
(The lower the gauge number, the thicker the wire.)

Q: What size power and ground wires do I need for my amplifier?

Using thicker power and ground cables will allow your amplifier to draw the juice it
needs from the battery more easily.

A: Before you can decide on the appropriate gauge wire for your installation needs, you
need to figure out the current demand of your system.

To do that, you must ascertain the approximate current draw (in amperes) of your
amplifier (or amplifiers). First, calculate the total power of each amp (multiply the
number of channels by the number of RMS watts per channel). If you have multiple
amps, add up the total power figures to arrive at a grand total. Second, double your grand
total power figure. And, finally, divide by 13.8 — the result is your system's approximate
current draw in amperes.

A cable gauge selection chart will help determine the proper gauge wire according to the
current demands of the system and the required length of the power wire.

Q: How much air space do I need around my amplifier?

A: An amplifier produces heat, which its heat sink absorbs and dissipates. You should
leave a few inches of air space around the amp so that it stays as cool as possible. When
mounting an amp on a side wall (vertically), make sure that the fins on the heat sink are
also running vertically so the heat escapes more easily. Don't mount an amp upside down
— the amp will not be able to dissipate heat effectively, and overheating can damage or
destroy your amp!

Q: How do I hook up multiple amplifiers?

A: You must supply power from your battery to every amplifier in your system. You
could run a separate power wire to each amplifier, but a power distribution block will
give you a cleaner installation with less potential for noise problems.

Let's say that you want to install a 200-watt mono subwoofer amp, a 75W x 4 amp for
your door and rear deck speakers, and a 30W x 2 amp for your dash speakers — 560
watts of total system power. Run a single 4-gauge power wire from your battery to a 3-
way (or 4-way) distribution block next to your amps. From the block, 8-gauge cables
supply power to your subwoofer and multi-channel amplifiers, while a 10-gauge wire
feeds the 30 x 2.
                                                                                           73


Ground your amplifiers in reverse fashion — one 10-gauge and two 8-gauge ground
cables run from the three amplifiers to a grounding block. A 4-gauge ground cable
connects the grounding block to your vehicle's chassis. You'll need a relay on the turn-on
lead to protect your receiver. A relay connected to the power antenna lead draws little
current from the receiver, but supplies enough power to turn on all your amps
simultaneously.

You can use RCA patch cables to send signal from your receiver to your amplifiers. A
receiver with 3 sets of preamp outputs can provide signal for your front, rear, and
subwoofer amps. If your receiver has only one set of preamp outputs, you'll have to use a
Y-adapter to provide signal to a multi-amp set, or look for amps with built-in preamp
outputs (allowing you to daisy chain the signal from one amp to the next).

Q: Where should I ground my amp?

A: Your ground wire should be of the same gauge as your power wire and must make
direct contact with the body of the car. Look for an existing bolt or screw that makes
contact with the car body near the amp. Remove the bolt or screw, and scrape away any
paint or grime.

A star washer will help your ground wire maintain solid contact with the car body. Use a
ring terminal on the end of the ground wire, to keep it securely fastened to the bolt or
screw.

If you can't find a convenient ground screw or bolt, drill a hole for one. Be careful not to
drill into the gas tank, a gas line, or a brake line.

If you're grounding multiple components, try to ground each one separately, with about a
half-inch of space between each of the grounding points. If you'd rather use a single bolt,
place the ground for the most current-hungry component (probably the biggest amp)
closest to the body of the car. Put the ground for the component that draws the least
current (probably the electronic crossover) on top.

Q: What's the difference between "parallel" and "series" wiring?

A: When you wire a pair of speakers in parallel, you connect the positive (+) leads of
both speakers to the amp's positive (+) terminal and the negative (-) leads of both
speakers to the amp’s negative (-) terminal.

If you parallel wire two 4-ohm speakers, the amp sees a 2-ohm load. This lower ohm load
(lower resistance) pulls more power from the amp and causes the amp to run hotter.
Amps that can handle this additional heat build-up are considered 2-ohm stable.

Series wiring works the same way as flashlight batteries; the positive end of one speaker
is connected to the negative end of the other speaker. Wire from the positive terminal of
the amplifier to the positive terminal of one speaker. Then wire from the negative
                                                                                              74


terminal of the first speaker to the positive terminal of the second speaker. Finally, run a
wire from the negative terminal of the second speaker to the negative terminal of the
amplifier.

If you series-wire two 4-ohm speakers, the amp will see an 8-ohm load. This higher ohm
load (higher resistance) inhibits the flow of current out of the amp. You get less power,
but the amp runs cooler and is more stable.

You can run more than one speaker from a single amp channel by wiring the speakers in
series or in parallel. Series wiring will raise the load (resistance) that your amp sees, and
parallel wiring will lower it. Be certain your amp is 2-ohm stable before wiring speakers
in parallel.

Capacitors
So, you've brought home your shiny new capacitor in the bag. If this is your first cap
installation, your first hope is that it came with good installation instructions. If not, or if
you just want to know how its done, perhaps this article will get you off to a good start.
Some capacitors require you to pre-charge them to attain usability mode. To do this, you
will need the charging board that comes with the unit. It is usually a simple PC board
card with a positive and negative 16 gauge wires. Simply follow the included
instructions, administering the power wire from a 12V source to your cap's positive
terminal. Don't forget to ground it too. Now connect the card, positive-to-positive and
negative-to-negative (or ground). When the indicator on the card comes on, the capacitor
is fully pre-charged.

At this point, its time for the installation. Select a good spot, no more than 18" from the
amplifier on the + power wire. Cut the power wire on the amp at the location where the
cap is to go, and connect the wire to the positive terminal. If you are using ring terminals,
install the first one flat on the base of the terminal. Then, run the second half of the
spliced power wire from the same positive terminal (set the second ring right on top of
the first one) and run it to the fuse block. If you are installing a model that uses a
distribution block cap, simply hook the wire to the amp in the appropriate slot, and the
12V lead (to battery) in the appropriate slot. As always, follow the instructions.

Don't forget about the ground (-) connection! The cap should be grounded close by,
preferably in the same spot the amp is grounded. Using the same gauge wire, run the
ground cable to the negative terminal (usually the one not marked). Next, if your cap
came with a remote lead terminal, run this to either the ACC fuse in your fuse block or to
the REMOTE/ANT lead on your receiver using 16 gauge or so wiring. With the wiring
all in place, secure the cap into place using an included bracket (if included) or using
some 3" pipe brackets from Home Depot. You can install the cap right side up, upside
down, side ways, diagonally, or whatever. Just make sure the vent at the top is never
covered or blocked.

You can now proceed to safely reconnect your battery terminals. Sit back and enjoy
cleaner, crisper and faster response, from your bass system.
                                                                                           75


Equalizers and Crossovers
Most of the time, an equalizer is installed in the passenger compartment. It is usually
mounted above or below the receiver in the factory radio location. If there isn't enough
room there, it can be mounted below the dash with a bracket or special kit.

Wherever you decide to mount your equalizer, you'll need connections for 12-volt power,
ground and a turn-on lead. In addition to the power connections, you'll need to feed signal
from your receiver. Usually this will be a single set of patch cables. If your receiver
doesn't have preamp outputs, you'll need an output level converter to adapt the receiver's
speaker lines to a preamp connection.

You will connect the equalizer to your amp with more patch cables. How many depends
on your EQ and amps, but you'll need at least one set of connections per amp. Be sure to
run your patch cords down the same side of the car as any speaker lines. Don't run them
on the same side as the power cable for your amp. That's a sure way to add noise to your
system.

Crossover/Equalizer Installation Guide

This installation guide offers examples of crossover and equalizer (EQ) installation types
and suggested system layouts. The installation of your crossover or EQ will depend on
the make and body style of your vehicle as well as the equipment purchased.

Tools needed, depending on vehicle

A note about wiring: In addition to the tools listed above, your EQ or active crossover
installation will require power and ground wiring, plus RCA cables, terminals, and a
remote turn-on lead. The easiest way to get all of these items is in an amplifier wiring kit,
available at crutchfield.com.

Passive crossovers: A passive crossover steps into the signal path after the amplification.
It's a capacitor or coil usually installed right on your speaker lead. Crutchfield carries
passive low-pass crossovers called Bass Blockers. To install:

1. Remove your speaker from its location in your doors, dash, or other (see Speaker
Installation Guide or your Crutchfield MasterSheet for more details). Disconnect the
positive speaker lead from the speaker, and connect the bass blocker to the speaker in its
place. Connect the positive speaker lead to the other end of the bass blocker, and test the
speaker's operation. Re-install your speaker.


To install a bass blocker: disconnect the positive speaker lead from the speaker, and
connect the bass blocker to the speaker in its place. Connect the positive speaker lead to
the other end of the bass blocker, and re-install the speaker.
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Active crossovers: Installing an active crossover requires a little more work. You have to
connect 12-volt power, ground, and a turn-on lead. The active crossover gets installed
between your receiver and your amplifier. (Many active crossovers have both speaker-
level and preamp inputs, so they can usually accommodate either type of connection.)
The outputs will be preamp connections to your amplifier. To install:

1. Mounting the crossover:
A crossover can be securely mounted with just a few screws. Anywhere between the
receiver and the amp is fine. Most people mount the crossover in the trunk near their
amp, especially if you have more than one amp. This also makes it easier to add
additional amps later. You should mount it where it will be easy to get to so that you can
make adjustments without too much trouble.Don't mount your electronic crossover
directly on steel — you will invite noise problems. Instead, install it on a non-conductive
board and attach the board to the car body (or use rubber grommets under the screws to
isolate the crossover).

2. Making the power connections: Your crossover will require 12-volt power, ground,
and turn-on signal.
To obtain 12-volt power: Cut a length of small-gauge cable (16 gauge is typically
sufficient) long enough to reach from the crossover location to your vehicle's fuse panel.
Strip one end of the wire, and attach it to the crossover's power input. This may require a
crimp-on connector, or bare wire might be sufficient, depending on the equipment you're
installing. Route the wire from the crossover location to your car's fuse panel. Using a
fuse tap, connect the wire to a source of switched 12V power.
To ground the crossover: Remove a bolt near the crossover mounting location. Crimp a
ring terminal to one end of a length of small-gauge wire, and then bolt the terminal
tightly to the vehicle's metal chassis. Scrape away any paint and clean the bolt location
thoroughly. If you can't find a convenient ground screw or bolt, drill a hole for one — be
careful not to drill into the gas tank or a gas or brake line.
Making the turn-on connection: In most cases, you can tap into your in-dash receiver's
amp turn-on lead to get a turn-on signal for your crossover. Remove the receiver from the
dash to access the turn-on wire (usually a blue wire. For step-by-step instructions on
removing your vehicle's radio, see your vehicle-specific Crutchfield MasterSheet, or read
our In-Dash Receiver Installation Guide. Strip the insulation off a small section of this
wire coming from the radio . Strip the insulation off another small-gauge cable that's long
enough to reach from the in-dash receiver to the crossover, then connect the two with
crimp caps or solder. Wrap the solder or crimp connection with electrical tape to guard
against a short. Using wire ties to secure the wire, route the turn-on lead behind your dash
all the way to the crossover mounting location.

Locate the remote turn-on lead behind your radio (usually a blue wire).


Connect the turn-on lead from your amplifier wiring kit to the blue wire. You can wrap
the bare wire ends together and cover with electrical tape, or use solder.
                                                                                         77


3. Making the signal connections: In most cases, you'll be routing RCA cables from your
in-dash receiver's preamp outputs to the inputs of your crossover. While your receiver is
out of the dash to access the turn on lead, connect a set of RCA patch cables (long
enough to reach your crossover in its mounting location) to these outputs, taping them
together so they won't come apart. Route the patch cables (again using wire ties) behind
the dash, and to the crossover mounting location.

Equalizers
Like a crossover, the equalizer gets installed between your receiver and your amplifier.
The outputs will be preamp connections to your amplifier. You'll find EQs that are
designed to be installed in the dash, above or below your receiver. Others are designed to
be mounted in a remote location, like the trunk. Either way, the wiring connections
required will be the same. To install:

1. Mounting the equalizer:
A remote-mount EQ can be securely mounted with just a few screws. Anywhere between
the receiver and the amp is fine. Most people mount the EQ in the trunk near their amp,
especially if you have more than one amp. This also makes it easier to add additional
amps later. You should mount it where it will be easy to get to so that you can make
adjustments without too much trouble. Don't mount your EQ directly on steel — you will
invite noise problems. Instead, install it on a non-conductive board and attach the board
to the car body (or use rubber grommets under the screws to isolate the crossover).

An in-dash EQ can be mounted above or below your in-dash receiver, assuming that you
have space available in the dash. This will require custom installation work. Another
option is installation below your dash, in a universal under-dash mounting kit. To install
the under-dash mounting kit, attach it to the mounting surface using the supplied self-
tapping screws. In most cases, the use of an under-dash kit will require modifications to
the kit or to the mounting surface.

Locate the remote turn-on lead behind your radio (usually a blue wire).

Connect the turn-on lead from your amplifier wiring kit to the blue wire. You can wrap
the bare wire ends together and cover with electrical tape, or use solder.

2. Making the power connections:Your EQ will require 12-volt power, ground, and turn-
on signal connections.
To obtain 12-volt power: Cut a length of small-gauge cable (16 gauge is typically
sufficient) long enough to reach from the EQ location to your vehicle's fuse panel. Strip
one end of the wire, and attach it to the EQ's power input. This may require a crimp-on
connector, or bare wire might be sufficient, depending on the equipment you're installing.
Route the wire from the EQ location to your car's fuse panel. Using a fuse tap, connect
the wire to a source of switched 12V power.
To ground the EQ: Remove a bolt near the EQ mounting location. Crimp a ring terminal
to one end of a length of small-gauge wire, and then bolt the terminal tightly to the
vehicle's metal chassis. Scrape away any paint and clean the bolt location thoroughly. If
                                                                                        78


you can't find a convenient ground screw or bolt, drill a hole for one — be careful not to
drill into the gas tank or a gas or brake line.
Making the turn-on connection: In most cases, you can tap into your in-dash receiver's
amp turn-on lead to get a turn-on signal for your EQ. Remove the receiver from the dash
to access the turn-on wire (usually a blue wire). For step-by-step instructions on
removing your vehicle's radio, see your vehicle-specific Crutchfield MasterSheet, or read
our In-Dash Receiver Installation Guide. Strip the insulation off a small section of this
wire coming from the radio. Strip the insulation off another small-gauge cable that's long
enough to reach from the in-dash receiver to the EQ, then connect the two with crimp
caps or solder. Wrap the solder or crimp connection with electrical tape to guard against a
short. Using wire ties to secure the wire, route the turn-on lead behind your dash all the
way to the EQ mounting location.
3. Making the signal connections: In most cases, you'll be routing RCA cables from your
in-dash receiver's preamp outputs to the inputs of your EQ. While your receiver is out of
the dash to access the turn on lead, connect a set of RCA patch cables (long enough to
reach your crossover in its mounting location) to these outputs, taping them together so
they won't come apart. Route the patch cables (again using wire ties) behind the dash, and
to the crossover mounting location.

Speaker Boxes and Enclosures
Wondering what is meant by Sealed, Ported, Bass Reflex, Acoustic Suspension? These
are all types of speaker enclosures or boxes, and all of these enclosure types are "direct
radiator" enclosures. They are called this because the sound is produced directly from the
"radiator" (the driver or speaker) without the assistance of a contrivance such as a horn.
Other types such as, Bandpass, and Coupled Cavity enclosures are similar, but more
complex.

Cardinal Rules for Enclosure Building

1. Build only for the internal volume size recommended by the woofer manufacturer.

2. Make the construction (sealed or ported) air-tight.

3. It is invariably more advantageous to buy, rather than build, both economically and to
assure quality of construction. If you are an experienced cabinet maker with the proper
tools, it will make a good project, otherwise....

Note, that enclosures exist solely for the purpose of accommodating the woofer. Tweeters
and midranges do not have to be enclosed at all, though for the sake of convenience they
are often mounted in enclosures along with the woofer. To help you decide which type is
best for your purposes, we offer below some detailed explanations and illustrations of
each type, along with information on the types of materials used in their construction and
a few suggestions.

Sealed Box
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The simplest direct-radiator system. The rear of the driver is in a sealed enclosure, and
none of the rear output of the driver contributes to the sound output. Depending upon
how stiff the mechanical suspension is Vs how stiff the enclosed air in the enclosure is
(and that's a function of the size of the box), you can have one of two enclosure types:
either an Infinite Baffle enclosure, in which the mechanical suspension is the dominant
source of system stiffness and the box is large; or an Acoustic Suspension enclosure,
where the air in the box is the dominating stiffness and the box is small. Sealed boxes
tend to be among the lowest efficiency systems for a given box size and bass cutoff
frequency. They are however quite good at reproducing a fairly broad range with little
deviation or distortion.

Vented Enclosures
Also the same as Bass Reflex, Ported, or Passive Radiator. Here, an aperture or port in
the box provides a means for the rear output of the cone to contribute to the total output
of the system. However, it only contributes over a very narrow range of frequencies. In
fact, in a properly designed system, the front output of the cone is reduced at the same
time the output of the port increases. Consequently the port does not re-enforce the output
of the woofer; it REPLACES the output of the woofer at these frequencies. If done
properly, this can significantly reduce distortion and increase power handling at very low
frequencies, a region that can be difficult for drivers. A vented system can be up to 3 dB
more efficient at certain frequencies than a sealed box system that has the same bass
cutoff frequency and size.

Bandpass
These are compound systems in that they have at least two enclosures: one on the front
and one on the rear of the driver. The enclosure on the front, which looks remarkably like
a vented box (because it is), acts as a low pass filter and can couple the output of the
woofer more efficiently to the outside. They have several useful advantages. For
example, the front enclosure can be used as a very effective acoustic crossover, filtering
out mechanical noises generated by the woofer, something no electronic crossover can
do. For very low frequencies, such an acoustic crossover can be far less expensive and
more easily designed than an equivalent electronic crossover. They are called "Bandpass"
because the combination of the rear enclosure and the driver form the high pass portion
while the front enclosure forms the low pass section. Making the bandwidth of the system
narrower raises the efficiency of the system.

Coupled Cavity
A variation of Bandpass and vented systems, the coupled cavity enclosure is the result of
attempts by designers to solve specific problems. These enclosures consist of two or more
rear enclosures, each coupled to the next by a vent. Each enclosure/vent combination is
another resonant system, and the combination is, essentially, a high order, multi-tuned
resonant system. Generally, these systems have quite complex response and are difficult
to design. No comprehensive theory on their operation exists like that for sealed, vented
and Bandpass systems.

Impedance Matching
                                                                                             80


Many builders and users like to take advantage of the power advantages of operating the
amplifier in bridged or mono mode. To do so however, means that the impedance
requirement of the drivers is taken into account when designing a proper circuit.

For this purpose, we have provided an impedance calculator

Materials
What is the best material to make speaker boxes? An ideal speaker cabinet material
would be very stiff, so that it would tend to be stable with variations in box air pressure.
It would also be very well damped, so that if it ever does deflect from air pressure, it will
come back to the original position without resonating.

In addition, it would have a very high resonant frequency (supersonic), so that low
frequency box air pressure would not cause it to resonate. An attractive material is
preferred, and additional credit is given for a material that is easy to cut, glue, and finish.
A great material would be cheap, too. Finally, it would be nice if the material were light,
because we all have to move our speakers sometimes, and it's hard to appreciate good
speakers with a sore back.

With all of those attributes, it would seem that no material is perfect. However, there are
many materials that have enough of the above good attributes to make excellent speaker
cabinets. Each, however, has advantages and disadvantages. In the list of good speaker
box materials below, the following code letters are used to indicate which attributes the
material possesses:

S = Stiff - D = Damped - H = High Resonance
A = Attractive - M = Malleable
C = Cheap - L = Light.

MEDIUM DENSITY FIBERBOARD (MDF)
Code: SDMC
This is the most practical material for quality speaker enclosures. It's extremely rigid and
resistant to sympathetic vibrations in thicknesses over half an inch. It cuts very nicely and
has a smooth surface. It takes veneer very well. However, bring a helper when you pick
the stuff up; one sheet is very heavy. MDF is harder on tools than common wood, but
easier than particle board. This is the material that many great speaker makers use.
Approximately $45 for a 4'x8'x1" sheet. Density: 50-lbs./Cu. ft.

POLYCARBONATE (LEXAN)
Code: DMA
A clear or solid-color polycarbonate box can look strikingly good. However, this is not a
cheap material. To locate it, look in the classified directory under PLASTICS.
Approximately $400 for a 4'x8'x0.5" sheet. Density: 75-lbs./Cu. ft. Acrylic (Plexiglas) is
cheaper than Polycarbonate, but weaker and not as well damped (not recommended as a
main construction material, but used for "windows" in Bandpass enclosures).
                                                                                           81


PLYWOOD SPACED AND FILLED WITH SAND OR LEAD SHOT
Code: SDAMC
Not a good choice for Car stereo because of weight issues.
If you have time on your hands and want a great impractical box, try this. Make a simple
box out of common plywood. Then glue cleats on the outside of the box to space the
outside plywood from the common plywood. Glue hardwood-veneered plywood to the
cleats and pour sand or lead shot into the spaces between the cleats. It won't be light, but
with the filler, it will be extremely well damped. In addition, if you use strong cleats and
glue well, the box will be extremely stiff. One designer was known to use different size
Sonotubes as an alternative to plywood, and filled the space between them with sand. Be
sure to sterilize the sand in your oven before putting it in the box.

ALUMINUM SHEETS FILLED WITH ALUMINUM HONEYCOMB (Aerolam)
Code: SDHL
Airplanes use this material for flooring. Next time a plane crashes in your neighborhood,
see if you can get the wreckage for your next speaker project. You can't get a better,
lightweight material. If you're really ambitious, you can make your own sandwich out of
high-quality plywood faces and a thick honeycomb core. You will probably need an
epoxy to glue the honeycomb to the plywood. A home-brew sandwich is easier to cut and
glue than Aerolam.

FORMED CONCRETE
Code: SDHC
Not a good choice for car speakers due to weight. There are tricks to working concrete,
such as to cast braces, rebar, and steel-wire right into the mix. Also, some types of
concrete are better damped than others. Remember to oil your concrete forms so that they
can be removed. Most concrete speakers use an MDF front panel, but you can pour one if
you use cardboard tubes or plywood rings to mold the concrete into the shape of a
speaker cutout.

Alternately, you can make a common veneered plywood speaker box and cast concrete
inside it for stiffening. Any box can be improved by making the walls thicker, by bracing
the walls, and by stiffening the walls. The stiffness of a material goes up as the cube of
the thickness, so a slightly thicker material is much stiffer. A thicker panel will also have
a higher resonant frequency because the stiffness goes up faster than the mass. Consider
lining the inside of your speaker with ceramic tile, attached with thinset mortar. You can
get tile remnants cheaply. They are easy to apply and can be added as an afterthought to
an imperfect box. However, be sure to attach all braces before tiling, because it is hard to
attach anything to tile. Also consider bracing any weak parts of the box. For example, all
joints will benefit from a wooden cleat. The back of the box will benefit from stiffeners
where the speaker terminals are attached. Most importantly, brace the front panel, or
make it out of a double thickness of material.
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