Car Handbook

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					Knowledge is   Power. And when it comes to C A R AU D I O ,
                       Power is           Everything
                                           Tips, Tweaks And Common Sense
                                           About Car Audio
Dear Car Audio Enthusiast:
Are you ready to choose—and possibly install—
a new car audio system? Are you thinking of
upgrading your current system with new speak-                                            The Basics
ers, amps or components? This booklet will help
by providing a general overview of some of the
                                                                                           (or the stuff
                                                                                            you gotta have)
major issues in car audio today, from how to
decide what to buy, to how to troubleshoot and
tweak your system. Because it’s our passion,
we’ve included some basic info on how speakers
really work, and how to get the most from your                                                                                                  Subwoofers
car speakers. And we’ve also taken some time to
                                                                                                                                                Subwoofers are the speakers that deliver the
answer your most pressing car audio questions.
                                                                                         Head Unit                                              lower frequencies of the audio spectrum. They
We’ll give you the inside scoop on the industry;                                                                                                need to be specially installed, usually in a box
                                                                                         The head unit is the tuner, cassette deck, or CD
you’ll find information here you wouldn’t nor-                                                                                                  designed specifically for them. They demand
                                                                                         player that sends the signal to the rest of the
mally find in equipment manuals. We believe                                                                                                     more power to play at acceptable levels without
                                                                                         system. Some head units have amplifiers built in
that the more you know, the easier it will be for                                                                                               distortion, which brings us to…
                                                                                         (in which case you must make sure your speakers
you to make intelligent car audio decisions.
                                                                                         are efficient enough to play loudly with the rela-
In case we’ve missed anything, or you have
                                                                                         tively small amount of power in most head units        Amplifiers
                                                                                         – See the Power Up! section). On a budget? Buy
questions concerning something that is not
                                                                                         speakers first. Better speakers can make your          An amplifier boosts your signal power,
covered here, please don’t hesitate to call Polk
                                                                                         stock head unit sound really good. You can             resulting in a cleaner sound and more volume.
Audio’s friendly Customer Service Department.
                                                                                         upgrade it later. And you will want to. One thing      And because more power is a good thing, an
In North America, call (800) 377-7655, Monday

                     a n o t e f ro m
                                                                                         to keep in mind: make sure the head unit has           amplifier might be the next thing on your list.
through Friday, 9:00am through 6:00pm, EST.
                                                                                         pre-amp outputs when you buy it. You'll need           Be careful, though, because if you are planning
                                                                                         them when you’re ready to add amplifiers later.        on adding several high power amplifiers
Happy Motoring!
                                                                                                                                                you may need to upgrade your car’s electrical

Matt Polk               Matthew                                                          Speakers
                                                                                         Ultimately, the head unit source sends its signal
                                                                                                                                                system with upgraded capacitors, battery,

Speaker Specialist

                          PS – There is also a wealth of information and useful advice

                          about audio in general, and my whole line of car and home
                                                                                         to the speakers. Your speakers determine how
                                                                                         your whole system will sound. No equalizer,
                                                                                         amplifier, or processor can compensate for poor
                                                                                         (or poorly installed) speakers. Even if you’re on a
                                                                                         budget, you should plan on spending the bulk of
                                                                                         your allotted expenses on your speakers. (And if
                          speakers in detail, on our website at       you’re really on a budget, plan on a head unit
                                                                                         and a set of speakers now, and worry about
                                                                                         amps and processors later.)

                      2                                                                                                    Polk Audio®, The Speaker Specialists®   3
                          More About More toys (or,
                           Amplifiers important stuff
Amplifiers can really turn your system on. With more power you’ll achieve a
cleaner, more dynamic sound at higher volumes. But installing an amp your-
self can be tricky. Be sure to plan your install carefully.

                                      you also need)
Never mount amps or other components directly to the metal of your car.
(That’s just asking for noise problems.) Instead, use screws with rubber isola-
tors when you have to mount to metal, or mount the component to a non-
conductive board and then mount the board to your car’s body. And before
you drill holes to mount anything, hook the component up and give it a
                                                                                  These are good times. There is no end to the
                                                                                  cool stuff you can add to your car audio system
                                                                                  these days. From the biggest, baddest sub-
                                                                                                                                        their own fuses to protect your components. You
                                                                                                                                        can also find battery terminals that have sec-
                                                                                                                                        ondary connectors to let you easily hook up the
                                                                                  woofers, to computerized navigation systems           extra power cables. Told you it was a good time!
test run in your chosen location. How smug will you feel after finding that a
                                                                                  (some that are even voice-controlled). Soon,
noise problem can be fixed simply by moving your amp to a new location…                                                                 To easily integrate a head unit to your car’s fac-
                                                                                  you’ll even be able to get your hands on com-
before you’ve drilled!                                                                                                                  tory wiring, use a wire harness. It allows you to
                                                                                  plete DVD “car theater” systems. The options are
                                                                                  endless. What’s more, there is even some cool         do all sorts of alterations without harming your
Amps are sensitive to electrical and motor noise, and they can interfere
                                                                                  stuff that you positively need (as opposed to the     car’s factory wiring. You want to replace your
with your radio reception. They should be mounted at least 3 feet away
                                                                                  cool stuff you just want), like this:                 stock head unit, but you don’t want to have to
from your head unit.
                                                                                                                                        leave your custom unit in the car when you sell it
                                                                                  You’ll need RCA cables to carry pre-amp (low line     in a year? So you use a wiring harness that’s
You can mount an amp under a front seat. This is close to your head unit, so
                                                                                  level) signal, usually from your head unit to your    designed for your car model, and you can
you’ll be able to use shorter cables to both the head unit and the speakers,
                                                                                  amp and processors (crossovers, equalizers, etc.).    remove your stock head unit and attach a new
but larger amps won’t work here.
                                                                                  Get ‘em well-built, flexible and shielded, with       one without cutting the original wiring. The
Mount an amp on the passenger side firewall; you won’t have to remove             sturdy connector ends that will withstand the         custom unit just plugs right in to the harness!
the seat, but again only a very small amp will fit.                               stresses of car audio connections. It pays to buy
                                                                                  quality cables.
Better yet, mount your amp in your trunk, where it will have plenty of
room to breathe, which is important because…                                      Amplified signal (especially when it’s going to
                                                                                  your subwoofer) is much stronger, and requires a
Amps produce a lot of heat. You’ll see cooling fins on an amp. They radiate       more capable cable. There’s a lot of current zip-
that heat into the surrounding air to help cool the amp. For these fins to        ping out of your amps. That’s why they make
operate properly, they need a few inches of air space around them at all          speaker cables. Be sure to use cable that is 16 to
times. Also, try to keep them vertical. Amps should not be mounted with           8 AWG (gauge) for subs and coaxes. (The lower
the fins facing downward (because heat will radiate back up into the amp).        the number, the thicker the wire, the less resis-
                                                                                  tance; thicker is better.) Tweeters and mids can
A tip: Just because something is metal doesn’t mean it’s a good ground.           use thinner cables (16-12 AWG).
Ground your amp directly to areas of heavy chassis metal only, not to a
piece of metal that’s merely attached to the chassis. Use ground wire run-        For battery connections, a power distribution
lengths of 18"-24" maximum.                                                       block can make wiring multiple electronics a
                                                                                  breeze. Run a 4 to 6 AWG power cable from
                                                                                  your battery to a power distribution block and
                                                                                  use its multiple outputs for each component.
                                                                                  Some power distribution blocks even come with

                      4                                                                                            Polk Audio®, The Speaker Specialists®   5
How Speakers Work
(or, it’s just moving
                                                                                                                Some things are just true. The sun rises and sets. Christmas comes every
                                                                                                                year. Subwoofers need power. They need more power than anything else in
                                                                                                                your system. This is simply because they are bigger, and need more power

air, but, man listen
                                                                                                                to move their cones farther than other types of speakers. If you have an
                                                       Speaking of Speakers                                     amp supplying 50W to each of your four front and rear speakers, you can
                                                                                                                bet on needing at least 100W for your sub(s). And you need to use a low-

to it move!)                                           Coaxial/Three-Way speakers (or “three-ways”)
                                                       are two (or more) speakers built into the
                                                       same frame.
                                                                                                                pass crossover to block the high frequencies from getting to your sub-
                                                                                                                woofer and messing up the mix.

                                                                                                                Low frequency signals reproduced by subwoofers are “non-directional.”
                                                       Advantages: They are inexpensive and easy to
                                                                                                                That is, it’s most difficult for humans to tell where lower frequencies are
Simply, speakers are air pistons that move back                                                                 coming from. So you can (theoretically) put a subwoofer anywhere without
                                                       install, often fitting into vacated factory loca-
(on the negative cycle of an electrical signal) and                                                             worrying about a loss of sound quality due to poor aiming and direction.
                                                       tions. Because coaxial woofers and tweeters
forth (on the positive cycle) creating different
                                                       are coordinated in one housing, you’re
degrees of air pressure. These movements trans-                                                                 To make bass response more effective, subwoofers must be housed
                                                       assured good imaging.
late into different frequencies that translate into                                                             in a “subwoofer enclosure.” That would be a box. With a subwoofer
Mozart or Metallica at your eardrum.                                                                            in it. Because of this, subwoofers are most often placed in a car’s trunk.
                                                       Disadvantages: They lack the flexibility
                                                       of separate components, and you can’t                    A subwoofer enclosure can be simple ("sealed”), or complex (bandpass,
To do this, an amplifier produces electrical                                                                    that’s pretty complex). Each kind of enclosure has its own characteristics,
                                                       aim them. Coaxials come with simple
impulses that alternate from positive to negative                                                               and the “one size fits all” rule of stretch denim and baseball caps does
                                                       crossovers built-in, and for the most
voltages and create an electromagnet when they                                                                  not apply here.
                                                       part you’re stuck with them. You can’t
    reach the “voice coil” (a spool of wire) inside
                                                       add your own external crossover to bet-
         the speaker. This electromagnet will                                                                   Ask us (go ahead, ask us), and we’ll say that bigger is better. But—
                                                       ter customize and control your sound,
              then either be repelled or attracted                                                              honestly—a good quality, well-enclosed 8" will outperform a cheap
                                                       although Polk’s got a new line of dX coaxes
                 by the fixed magnet at the                                                                     12" sub any day. Big, cheap subs have slower responses and can sometimes
                                                       that welcome an external crossover. Just thought
                    bottom of every speaker.                                                                    be “boomy,” while smaller subs tend toward a tighter sound. A bigger sub
                                                       I’d throw that in.
                      The voice coil is attached                                                                also needs a bigger box in which to enclose it. And if you fill up your trunk

                        to the speaker cone, and                                                                with a giant sub box, how are you going to haul the bodies?
                                                       Separates, or components, are sets of separate
                         it moves the speaker
                                                       woofers and tweeters with an external crossover.
                           cone back and forth                                                                  If you’re going to go “big,” don't skimp. Do it right.
                            as it’s attracted or

                                                       Advantages: More placement/system flexibility,
                             repelled. The surround    and a better crossover.
                             (a rubbery circle that
                              joins the top of the     Disadvantages: Placement flexibility means you’ll

                                                                                                            (or, the sub is
                              cone and the speaker’s   be drilling holes in your car to put separates in
                             metal basket) and the     custom locations. You may be able to mount the
                             spider (a circle of       woofer in the place vacated by your factory

                                                                                                            greater than
                            corrugated material        speaker, but you’ll still need to make a separate
                          that joins the bottom        hole for the tweeter. (The most common place to
                         of cone to the speaker’s      install tweeters is in the top front corner of the
                        magnet) make the cone

                                                                                                            the parts)
                                                       door panel.)
                      return to its original posi-
                   tion. All this moving around        Subwoofers add the lower frequencies to a
                makes “sound.”                         whole system. We could have a whole section on
                                                       subwoofers alone. In fact, here comes one now:
                      6                                                                                                Polk Audio®, The Speaker Specialists®   7
Sub                                                                                             Listen To The Man
                                                                                                (or, how to avoid the
Free Air: Free air subwoofers use the whole trunk as their enclosure.
                                                                                                5 Biggest mistakes in
                                                                                                buying car audio)
If you’re driving a hatchback (stop this now) this won’t work, since the
trunk has to be sealed as tight as possible for the woofers to get any
benefit. Free air subs are not very accurate and are unpredictable—                             When you walk into your local, friendly car            fun of it. You couldn’t be more wrong. Answer
sometimes they sound good, sometimes they sound really really bad—                              audio sales emporium, the smiling pleased-             this question, and establish boundaries for the
                                                                               Seat             ta-meetcha sales professional is going to lob          extent of your installation. It will affect the type
and they require a lot of power.
                                                                                        Trunk   a bunch of questions your way. You’re first            of system you buy, and the type of installation
Sealed: Sealed enclosures are the most common kind of box, and the eas-                         thought is: “Why should I share all this personal      the expert suggests.
iest to build. They deliver the flattest frequency response and best sound                      information with this stranger?” And that’s a
                                                                                                good reaction. But it’s just a car stereo, man.
quality. Make sure you get the size right, since a box that’s too small will
deliver tighter bass but suck up more power from your amp, and a box                            The salesperson is there to help you pick the
                                                                                                                                                       Question #3:
                                                                                                                                                       How long are you going to keep your car?
that’s too big will simply sound muddy. Use about 1 lb. of loosely packed                       best system for your needs. They can take your
damping material per cubic foot of enclosure volume when you’re build-                          end of the equation and add to it their own
                                                                                                                                                       You agree to the most extensive and complicated
ing one, being sure to keep the fill out of the speaker’s pole piece vent.                      experience and knowledge of the products they
                                                                                                                                                       installation of the most expensive system in the
Polk Audio makes subs specifically for a sealed enclosure (our dX Series).                      sell, and help you come up with the perfect
                                                                                                                                                       hemisphere. And when you get home you
So we definitely recommend this type of box.                                                    system for your budget and your car. So relax.
                                                                                                                                                       remember that you planned to sell your lemon
                                                                                                Answer the questions. Now.
                                                                                                                                                       at the end of the month. The answer to this
Ported: Ported enclosures are usually bigger than sealed enclosures and
                                                                                                                                                       question can help you avoid that.
feature a “tube” or port that lets air out of the box. The theory is that a
speaker port pushes and pulls the air at the same time as the woofer,
                                                                                                Question #1:
thus reinforcing the bass. The box itself can often act like an amplifier,
                                                                                                How much do you want to spend?
                                                                                                                                                       Question #4:
sometimes adding 3 to 4 dB to bass levels. Again, about 1 lb. of loosely                                                                               What is the primary function of your car?
                                                                                                The smiling sales professional is not asking
packed damping material is recommended per cubic foot of enclosure
                                                                                                this question so he can decide how big a sucker
volume (be sure to keep it away from the port). If you’re interested in                                                                                Do you use your car to drive to and from work
                                                                                                you are, he’s asking it so that he can help you
this type of enclosure, check out the Polk EX Series subwoofers.                                                                                       everyday? Is it a 10 minute jaunt, or an hour
                                                                                                budget your money in the most economical way.
                                                                                                                                                       commute? Do you travel to distant destinations
                                                                                                Your answer to this question helps determine
Bandpass: Bandpasses enclose a woofer between a sealed and a ported                                                                                    in your car? Does your car just sit in your drive-
                                                                                                where your money should be spent to build a
box. Sometimes both parts of the box are ported. Bandpass enclosures                                                                                   way until you’re forced to go to the grocery
                                                                                                system that’s right for you. He’ll probably sug-
yield more bass than sealed or ported boxes (especially at lower frequen-                                                                              store? Answering this question helps an expert
                                                                                                gest budgeting your money in the order of
cies), but over a narrower frequency range. The enclosure acts to block                                                                                decide how much of a system you really need. If
                                                                                                component importance: speakers, amplifier,
upper and lower frequencies. Bandpasses are big, hard to build, and can                                                                                you simply drive from home to work, you proba-
                                                                                                and then head unit.
be messy when precise volumes and port sizes are not followed. If you're                                                                               bly don’t need the same kind of extreme GPS
up to going the bandpass route, both the Polk dX and EX Series subs                                                                                    navigation and DVD surround sound that you
work extremely well in bandpass boxes with one enclosure sealed.                                Question #2:                                           would want if you were traveling long distances
                                                                                                What changes are you willing to make to your car?      on a regular basis. But then again…
A tip: When you’re working in your trunk, put duct tape over the trunk
latch so you won’t accidentally get trapped inside. Couldn’t happen to                          He’s grinning when he asks this. Maybe he’s
you, right? Just thought we’d mention it.                                                       salivating, too. You’ve got visions of a bunch of
                                                                                                installers completely gutting your car just for the

                      8                                                                                                           Polk Audio®, The Speaker Specialists®   9
Listening To Buy,                                                            You can get a good working demonstration of
                                                                             transfer function by listening to your current car

(or Little-Known
                                                                             audio system with the windows rolled up tight,
                                                                             and then with the windows rolled down. You'll
                                                                             hear that the bass is louder with the windows           And maybe standing in the sound room is the
                                                                             closed. That’s transfer function at work for you.       wrong position in which to listen to car audio

Secrets Of The                                                               Remember that when you hear a speaker in a
                                                                             showroom, it will have less bass than it will have
                                                                             in your car.
                                                                                                                                     demos. Do you listen to your car speakers while
                                                                                                                                     standing in your car? Sit down in the sound
                                                                                                                                     room, with the speakers you’re testing at

Sound Room)
                                                                                                                                     dashboard level. Notice where the speakers
                                                                                                                                     will be placed in your car. Are you sitting off-
                                                                             Dead Rooms and Live Cars                                axis, or directly in line with them? Pick an
You could fall in love with a system in the sound room, only to want a                                                               optimal pathlength by estimating how far
divorce once that same system is installed in your car. This is because      A “live” environment is one that is filled with         from the speakers you will be sitting when
there are big differences between sound rooms and your car. Listening        noise. Your car audio system has to compete             you’re in your car. Are you testing rear speakers?
area, listening position, and something called “transfer function” can all   with your car’s engine, other car’s engines, sirens,    Don’t stand in front of them, since that’s not
make the sound in the sound room much different from the sound that          road noise, and the sounds of the angry drivers         how you hear them in your car. Turn around
ultimately ends up in your car.                                              you’ve cut off. None of that exists in the sound        and sit facing away from them.
                                                                             room, which is “dead” to extraneous sound
                                                                             (especially if it is an insulated, padded space).
Room vs Car                                                                  Professional car audio installers will often dead-
                                                                                                                                     By keeping the differences between the room
                                                                                                                                     and your car—there will always be more bass
                                                                             en a car’s sound the same way room builders do          response in the enclosed area of your car—in
A sound room is different than your car. A sound room is just that (a
                                                                             when they build sound rooms. They apply                 mind when you’re testing out car audio, you’ll
room), while a car is… You get the idea. It’s apples and oranges. A room
                                                                             padding, fill gaps in doors and behind dashes,          be more prepared to make the right decision
has flat, hard walls set far apart. A car has any combination of soft
                                                                             tint windows, and even coat the inside of               when it comes time to buy the best sounding
curves and plush padding, hard vinyl and metal, all in an irregular space
                                                                             exposed metal with dense, sound-dampening               system for your car.
about the size of a refrigerator box. It’s rare that you get to test a car
                                                                             adhesive materials.
audio system in an actual car, so you need to know the secret to turning
these two completely dissimilar listening environments into more hos-
pitable conditions.                                                          Listen Different
                                                                             So the best way to listen in a sound room is to
Beware of Transfer Function                                                  try to duplicate the listening experience of your
                                                                             car. Keep in mind what kind of car you drive. Is it
That’s difficult because of a complicated physics equation called “trans-
                                                                             a big boxy metal car, or a snug soft two-seater?
fer function.” Transfer function is a measure of how the volume of an
                                                                             As a rule, different types of cars treat sound dif-
enclosure, such as a room or a car, effects the way a speaker sounds. A
                                                                             ferently. Basic models, with lots of plastic and
loudspeaker in your living room sounds different than a loudspeaker in
                                                                             metal, tend to make highs louder, while more
your closet because the living room is a larger space, and thus puts less
                                                                             luxurious cars, outfitted with soft fabrics and
pressure, or “backward load,” on the speaker. A loudspeaker in your
                                                                             more padding, will dampen the highs and make
closet sounds a lot like a speaker in your Miata, though, because they
                                                                             bass fuller. Keep the characteristics of your car in
are both small, enclosed spaces.
                                                                             mind when you’re standing in the sound room.

                    10                                                                                          Polk Audio®, The Speaker Specialists®   11
To Install or Not To                                                                                                 ‘A’ is for amperes, a measure of electric current. How much is
                                                                                                                     enough? (We like to say that having too much amperage is

Install, That is the                                  Power Tools Don’t Frighten You
                                                                                                                     like having too much money.) Your car’s stock alternator prob-
                                                                                                                     ably provides enough amperage to power a basic car audio
                                                                                                                     system. But if you want to add multiple high power ampli-

Once you’ve picked out your electronics,
you have to decide whether you are going
                                                      If you’re good with minor repairs, like changing
                                                      your spark plugs, you probably won’t be intimi-
                                                      dated by installing a sound system and you
                                                      might consider doing it yourself.
                                                                                                                     fiers, you might require some additional current, and the
                                                                                                                     installation of a new alternator or stiffening capacitors (see
                                                                                                                     the section with answers to your questions for more on alter-
                                                                                                                     nators and stiffening capacitors). Ampere is commonly abbre-
to install them yourself, or let a professional                                                                      viated as “amp” (not to be confused with amplifiers), but
installer do it. Maybe you’re handy with small                                                                       sometimes it’s “I.” Electricity is like that.
                                                      There are lots of good reasons to self-install. If
repairs, or maybe the thought of installing
                                                      you’ve got the time, and enjoy the challenge,                  A crossover is an electronic circuit that directs which frequen-
speakers yourself seems daunting but you
                                                      doing the install yourself might be pretty excit-              cies go to which speakers. For example, since subwoofers are
don’t know what qualities to look for in a
                                                      ing. Customizing your own car is a great way to                designed to best reproduce only the lowest frequencies, a
professional installer. Here’s some help.
                                                      express your creativity. Poking around in the                  subwoofer crossover (a low-pass crossover) allows only the low
                                                      interior of your car makes you, well, “intimate”               frequencies to pass through to the subwoofer. Freed from the
The Pros of Pros                                      with your automobile.                                          task of reproducing heavy bass, your other speakers will
                                                                                                                     rejoice by performing better and playing louder. You need
If you have any doubts, save yourself lots of grief   Manufacturers and retailers are usually very                   crossovers so that you don’t send unnecessary signals to a
and use a pro. Cars are more complicated today        helpful when it comes to DIY installs. Rely on                 speaker (which could damage it).
than ever before. Even basic models are packed        them for parts, wiring harnesses, tips, templates
with computer controls. Today’s state of the art      and general good advice. Like this:                            ‘dB’ is for decibel, a measurement of power ratios and vol-
upgrades—audio systems, navigation systems,                                                                          ume. All you really need to know is that to gain 3dB in vol-
even DVD systems—and their operating systems          Avoid some of the pitfalls of doing-it-yourself                ume (just enough to hear the difference), you must double
are interlaced in delicate and intricate ways.        simply by keeping some common-sense guide-                     your power. There. That’s it.
Meddling with these critical systems can shorten      lines in mind:
the life of your vehicle and even endanger your                                                                      ‘DC’ is direct current, a type of circuit. In a DC circuit, the cur-
life. Electrical problems, unseen shorts, wire        s RTFM: Read the instructions completely before                rent always flows in one direction. In your car, you’re dealing
deterioration, structural changes and loose con-        you begin.                                                   with a 12volt DC system (twelve volts of direct current). Hence
nections could become safety issues.                                                                                 the term, “12volt Guys.” In a car, it’s important to keep track
                                                      s Don’t take your car apart until you’re certain

                                                                                                           How To Talk
                                                                                                                     of which wires are attached to the ground (or “negative”)
Before you decide to let anyone work on your            you have all the tools you’ll need to put it                 lead of the battery.
car, check his or her credentials. The Mobile           back together again.
Electronics Certification Program (MECP) adminis-

                                                                                                           Like A 12Volt
ters a written test on the science and installation   s Avoid unnecessary discharge: disconnect the
of car sound. Make sure your installer is MECP          negative battery cable before you begin.
certified. Are they an ASE (Automotive Service

                                                                                                           Guy(Or, What Those
Excellence) certified mechanic? Ask.                  s Protect your upholstery with a drop cloth, and
                                                        don’t carry tools in your back pockets!
Check references as well. Ask to see examples of
previous installs and speak with previous cus-        s Give yourself plenty of time, don’t rush—don’t
tomers. Deciding on a professional installer is a       force anything.
lot like finding a reliable contractor or plumber.
                                                      s When in doubt, stop and ask directions.
                                                        RTFMA: reread the instructions.                    Technical Terms Mean)
                    12                                                                                       Polk Audio®, The Speaker Specialists®   13
‘Hz’ is for hertz, a measure of frequency. One hertz is equal to “one                                                                                               ‘Staging,’ like “imaging,” is a description of your
cycle” per second. A cycle of sound is the duration between similar por-                                      Trust your ears, not the specs                        system’s ability to “fool you” into thinking that
tions of a sound wave (between two peaks, for instance). Frequency can                                                                                              everything (including bass) is right in front of you.
describe both electrical circuits and sound waves, and sometimes both.                                        Specs can tell you how a speaker will                 Like on a stage (hence the term “staging”), the
For example, if an electrical signal in a speaker circuit is going through                                    sound, but they can’t tell you what a                 singer should (in general) be in the center, and the
one thousand cycles per second (1000Hz, or 1kHz), the speaker will res-                                       speaker sounds like. Trust your ears.                 band should be located to the left and right.
onate at 1kHz, producing a 1kHz sound wave. Got all that?                                                     And if you don’t know what to listen for,             Good staging (and good imaging) are not easy to
                                                                                                              trust someone with listening experience,              achieve in a car audio situation. One of the hard-
‘Imaging’ is a description of the illusion of being able to locate certain                                    like the professional in the showroom.                est aspects of staging is getting the illusion that
sounds as “coming from” certain places. If you have a system with good                                                                                              the bass is coming from the front of the car, even
imaging, the sound should seem to come from different distinct instru-                                                                     though the woofers are in the back. You may have to experiment with
ments and voices, not from speakers. A singer would generally be in                                                                        speaker locations, directions, and crossover roll-off points. Cheat the bass
front of you (center stage), and the band would be arranged around                                                                         by overlapping the frequencies played by your mids and subs so that
them. See also “staging.”                                                                                                                  your semi-directional mids actually “pull” the bass to the front. To do
                                                                                                                                           this, use a high-pass crossover to roll off your midbass drivers as low as
An Ohm is a measure of resistance and impedance
that tells you how much a device (like a speaker) will
                                                             Can your impedance be too low?                                                you can (without getting distortion). Then set your sub's low-pass
                                                                                                                                           crossovers at a slightly higher frequency. (See More About Crossovers,
resist the flow of current in a circuit. If the same exact   Yes it can. It all depends on how well your                                   which is coming up.) This will mix the bass coming from the front and
signal is sent into two speakers, one rated at 4 ohms        amplifier can handle the increase in current                                  rear, giving the illusion that the bass comes from the front. Adding a
of impedance, the other at 8 ohms of impedance,              flow that comes with lower impedance. The                                     center channel improves staging as well, but that’s next week’s lesson.
twice as much current will flow through the 4 ohm            more current, the hotter your amp will get. An
speaker as the 8 ohm speaker. All things being equal,        overheating amp is trouble. A good amp will                                  ‘THD’ is total harmonic distortion, or how much a device distorts a signal.
the 8 ohm speaker requires twice as much power to            simply shut down when overwhelmed with                                       These figures are usually given as percentages. THD figures below
achieve the same volume level, since power is propor-        current. A poor quality amp will burn. Make                                  approximately 0.1% are inaudible, but—like bad karma—distortion
tional to current. (See “dB.”)                               sure your amp can handle the impedence of                                    adds up.
                                                             your speakers.
‘Speaker Sensitivity,’ measured in dB, is how loud a                                                                                      ‘V’ is for volts, the measure of “electric potential.” Voltages don't do
speaker plays with a given amount of power going                                                                                          anything, they simple measure stuff.
into it. Conveniently, the usual measuring stick is 1 watt at 1 meter. A
higher sensitivity rating means that the speaker will play louder using                                                                   ‘W’ stands for watts, another measurement of electrical power. One watt
the same power as a speaker with a lower rating. So, should you always                                                                    is equal to one volt times one amp of energy per second. Don’t be mis-
buy the speaker with the higher sensitivity rating? Not necessarily,                                                                      lead by wattage specifications. All things being equal, a good, expensive
because you’ll usually end up trading off some other aspect of system                                                                     50W amplifier will outperform a cheap, marginal 75W amp. Here’s why:
performance like bass response or power handling. Sometimes a lower                                                                       In order to play even 3 decibels louder, an amp must double its power
sensitivity rating gives a speaker a better (flatter) balance of frequency                                                                output. The difference between 50 and 75W output is so small, maybe a
responses without sacrificing efficiency or value. How you announce                                                                       dB or so, that you probably won’t even be able to tell. The human ear
your intention to spend your paycheck building a car audio system is                                                                      just doesn’t pick that up. To actually double the apparent volume, you’d
your sensitivity rating.                                                                                                                  have to have a 10dB increase in level. Basically, you’re better off with a
                                                                                                                                          more expensive, more efficient, better built lower wattage amp than
                                                                                                                                          with that “200 Watt” amp you picked up for $39.95 at the flea market.

                     14                                                                                                                        Polk Audio®, The Speaker Specialists®   15
           More About
                                                                                                                                      Low Pass              HighPass
                                                                                                                   dB                                4300               Chose your crossover points and crossover slopes by
                                                                                                                   95                                                   consulting the frequency response measurement on
                                                                                                                   90                                                   your speaker specs. The frequency response is the range

                                                                                                                   85                                                   of frequencies that the speaker can successfully repro-
                                                                                                                   80                                                   duce. The frequency response of two separate speakers
                                                                                                                                                                        (woofer and midrange, for example) must overlap a lit-
You can severely damage your speakers if you don’t pay attention to the                                                                                                 tle, or you will hear a “gap” in the music. The crossover
way your amps and crossovers work together. For example, if you’re forc-                                                                                                point appears within this overlap. The crossover slope is
                                                                                                                   65                                                   a measurement of how abruptly the crossover cuts off
ing too much high volume bass out of a smaller midrange or tweeter
                                                                                                                   60                                                   the speaker’s sound beyond that crossover point. If your
speaker, you’re going to force the speaker to its “excursion limit,” or its
limit of movement. The voice coil in the stressed out speaker bangs                                                55                                                   speaker frequencies overlap just a little, use a steeper
                                                                                                                        20      100         500 1K     5K 10K 20K       slope. The steeper the slope the narrower the range
around, gets bent out of shape, and destroys your speaker (see the sec-
tion on how a speaker works for more about speaker movement).                                                                                                           within which two speakers are producing the same sig-
                                                                                                                              Crossover Slope Diagram
                                                                                                                                                                        nal, and the smoother the transition from one speaker
Not surprisingly, this is a common problem with 4" and smaller full-                                                                                                    to the next. The opposite is also generally true.
                                                                                Woofer                  Tweeter
range and coaxial speakers. And equally unsurprising, there’s an easy
way to prevent it. Simply “roll off” speakers with an in-line capacitor—
or “bass blocker"—to keep the lowest bass frequencies from getting to
that driver. (You won’t be “missing” anything, since you’ll be filtering

                                                                                                                   What’s That Noise?
out frequencies the speaker can't reproduce anyway, and your sub-                                 HIGHS
woofer will easily pick up the slack.) Any good car stereo dealer can help     LOWS
you choose a capacitor value that's right for your speakers. They proba-
bly have them in stock, too.                                                                Passive                      Hiss. Hum. Noise. Every system is going to have       Check your head unit. If you stop hearing the
                                                                                                                         some noise. Unless you’re going to enter a sound      noise when you jiggle or pull out your head unit
There are two types of crossovers: active and passive.                                                                   competition, you may not even have to worry           while it’s playing a tape, the noise may be radiat-
                                                                                                                         about it. Usually, you won’t hear that small hiss     ing from an ungrounded component into your
A passive crossover appears in the circuit after your amplifiers, and                                                    when you’re driving. But if you’re concerned,         tape or CD system. Try shielding the back of your
                                                                               Passive Crossover
divides the signal that then goes to your speakers. A passive crossover                                                  you can test your system. Make sure your              head unit with metal foil (available at retailers)
has no power, ground, or turn-on leads and are rather inexpensive. But,                                                  amplifier is isolated from your car’s chassis.        or filtering the unit’s power leads.
they tend to be inefficient and can even add some distortion.                                                            Then, try this:
                                                                               Woofer                  Tweeter                                                                 Check the electrical system. Is your battery filled?
An active, or electronic, crossover does its job pre-amp (taking the signal                                              Check your RCA patch cords. Disconnect the cords      Have a mechanic check your alternator and give
directly from your head unit before it gets to the amplifier) and needs                                                  from you amp and reinsert just one strand into        your car a tune up. A tune up will stop the noise
an external power source. Active crossovers give you control over which                                                  the right and left input jacks of your amp. Now       at its source: the spark plugs, wires, distributor
frequencies you want to use as the crossover points for bass and treble.                                                 start your engine and turn on your system. If you     cap, and coil. Install resistor-type spark plugs
Some active crossovers allow you to customize the crossover slope as well      Amplifier
                                                                                                                         get noise, try re-routing your cords, separating      with shielded carbon-core wires. Worse case,
as the crossover point. Because they filter frequencies before the signal is                      HIGHS                  them from other connectors (like your power           have a mechanic check the grounding of your
amplified, active crossovers ensure that the amp gives its full attention      LOWS                                      cable) by at least 18". Also, try a better quality    ignition, charging, and injection systems. All of
to the filtered signal, which is very efficient.                                                                         of patch cord, consider trading in coaxial cable      these things can radiate noise into your system.
                                                                                          Active                         for “twisted pair” cables.

                                                                                                                         Check your antenna. Unplug it and see if the
                                                                                           Unit                          noise goes away. If it does, you need an antenna
                                                                                                                         noise filter.
                                                                                Active Crossover

                     16                                                                                                                                   Polk Audio®, The Speaker Specialists®   17
“Distortion” can destroy your speakers. Distortion is the audible expres-
sion of a speaker’s limitations or an amplifier running out of clean
power. Distortion happens when speakers are forced to play frequencies
that they were not meant to play, which happens when speakers lack
the proper crossovers (frequency blockers). If you don’t have the
crossovers, and you jam low frequencies through your little tweeters,
                                                                                               Power Up!                         For most systems, 30 to 50 Watts (per channel)
                                                                                                                                 should be fine for primary speakers. Apply more
                                                                                                                                 (two to three times more, or 100-150 Watts) to
you will hear distortion.
                                                                                                                                 your subwoofers. If you’re powering your tweet-
Since beauty, as it were, is in the ear of the beholder, there’s lots of                                                         ers independently, they can get away with less
argument over what distortion actually sounds like. But it’s safe to say                                                         power (20 - 40 Watts).
                                                                            How much power do you really need? A lot. But
that when the stuff you’re listening to gets “muddy,” when it starts to     all car audio components come with their own         A caveat: Speakers can be harmed when you
lose the definition of individual elements, when it all starts to blend     power handling specifications, and you should        push an amp beyond its power capabilities.
together into a loud jumble… That, my friend, is distortion.                start there when determining how much power          It’ll “clip” the signal, which produces both
                                                                            you’ll need.                                         mechanical and thermal stresses on a speaker’s
If you start hearing distortion, turn it down!
                                                                                                                                 voice coil. The speaker’s voice coil gets banged
                                                                            On amps, for instance, you’ll see two types of       around, overheats, and ultimately breaks. But
Distortion is bad. Power, on the other hand, is good…
                                                                            power specs: Continuous, and Peak (or Max)           you’re actually less likely to blow a speaker by
                                                                            power output. The continuous power output rat-       using too much power than you are by using
                                                                            ing is determined using a constant test tone. The    too little power. If you like to play it loud, get
                                                                            peak power output rating describes how much          a bigger amplifier.
                                                                            power the amp produces in short bursts. This is

Defeating                                                                   more comparable to the nature of music, which
                                                                            tends to go up and down a lot.

                                                                            For a speaker rated at 100 watts peak, you
                                                                            should get a 100 watts/per channel amplifier to
                                                                            safely get the greatest amount of volume from
                                                                            that speaker. If all you know is the continuous
                                                                            power of a speaker, use “The 3/4 Rule”: divide
                                                                            the continuous rating by .75 to calculate the
                                                                            maximum amplifier size. (For example, a speaker
                                                                            with a 50 watt continuous rating can be safely
                                                                            used with an amplifier of 70 watts/channel
                                                                            [50÷.75 = 66.7, round up to 70 watts].)

                     18                                                                                     Polk Audio®, The Speaker Specialists®   19
Questions                                                                                       Do round speakers sound better
                                                                                                than oval speakers?
                                                                                                                                                       thing you’ll find very hard to do by yourself.)
                                                                                                                                                       Play some music that you’re familiar with and

                                                                                                                                                       put the tweeter in different locations with your
                                                                                                                                                       buddy mirroring your placement. Listen for
                                                                                                For all practical purposes, yes. A round cone is
                                                                                                                                                       “staging” and “imaging.” When you find a
                                                                                                more rigid than an oval-shaped cone. At higher
                                                                                                                                                       spot that works well, mount them there, if
When I turn my music up, my headlights dim.                                                     sound levels, an oval-shaped cone will distort
                                                                                                more. Oval-shaped speakers are made to please
                                                                                                                                                       you can. If you can't put them where they
How come?                                                                                       the rear deck space considerations of many cars.
                                                                                                                                                       sound the best, compromise by mounting them
                                                                                                                                                       on the front door frame (inside, opposite the
                                                                                                One advantage of 6x9s, though, is that ovals
Your headlights dim because your system has caused a drop in the avail-           +        –    have more area, and thus move higher air
                                                                                                                                                       side view mirror) facing the space between
able voltage level of power for your car’s other, less necessary acces-                                                                                the two front seats.
                                                                                                volume and produce more bass.
sories (headlights, engine, etc.). Voltage drops can be caused by an
accessory’s large current demand, like an amp struggling to produce a
loud bass note. Get your battery and alternator checked. A low battery                          Where should I put my tweeters                         How do I tell if my speakers are in
can overload an alternator, drawing power away from your system. If                             for best performance?                                  or out of phase?
everything checks out okay, you could be making such large demands
                                                                                                                                                       If your speakers are out of phase, imaging will
on your electrical system that an upgraded alternator may be necessary.           +        –    The best thing to do is install the rest of the
                                                                                                                                                       be vague and bass output will be reduced. To
A “stiffening” capacitor can also be installed. A stiffening capacitor is                       system and leave the wires for the tweeters long.
                                                                                                                                                       ensure that your speakers are hooked up in
like an extra power supply for your electrical system; it keeps a small                         Grab a buddy (you’ve got one, right?) sit in the
                                                                                                                                                       phase, check to make sure that the positive and
reserve of 12V power. See your installer. If your car won’t start after you                     front street and have them hold one tweeter
play the stereo for a long time with the engine off, try paralleling           +           –    while you hold the other. (This helps you get
                                                                                                                                                       negative leads are connected the same way to
                                                                                  Amplifier                                                            both your speakers and your receiver or amp.
another battery into your system.                                                    or         them separated by the width of the car, some-
                                                                                  Crossover                                                            Make sure red is connected to red, black to
                                                                                                                                                       black, etc. Check for correct phasing… With a
My system “pops” when I turn it off.                                          Parallel Hookup                                                          9Volt battery. Disconnect the speaker wire from
How do I stop it?                                                                               Parallel vs. Series
                                                                                                                                                       the amp. Touch the wire you think is negative to
                                                                                                                                                       the negative battery terminal (the big one).
As you power down, transient signals in the processor sometimes find                                                                                   Touch the positive wire to the positive battery
their way into the signal path. The amp transmits them to the speakers,                         Wanna play it loud? Try wiring your subs in a          terminal (the other one). If your speakers are
and POP! Add some “turn off delay” to your head unit. See your manu-                            Parallel hookup. A Parallel hookup lowers              wired in phase, the speaker cone will move
                                                                                                speaker impedance (for example, when two
al, or your installer. Or, read this: You can add delay by adding a 1N4004    +        –        4 ohm subs are wired together, their impedance
                                                                                                                                                       “out” and stay there. If they are out of phase,
diode in series with the processor's turn-on lead, with the striped side                                                                               the driver cone will move “in” and stay there.
towards the equalizer. Then add a capacitor in parallel, the (+) side of                        equals 2 ohms), and the lower the impedance,           (This won’t help you for tweeters, only
the cap to the striped (processor) side of the diode; the (-) side of the                       the more current is delivered. This higher             midranges and woofers. So when you’re
cap to ground (not the radio or eq chassis, connect it directly to the                          current makes for some real volume, especially         wiring your tweeters, be careful. Do it right
car chassis). Fiddle with the cap value to get the amount of delay                              in your subs. But your amp’s gotta be able to          the first time.)
you need before the eq shuts off; not too long, just long enough to                             handle low impedance to be wired in a Parallel
                                                                                                hookup. Parallel hookups suck a lot of power,
make sure the amp is off before the eq powers down (220 - 1000 uF).           +         –       and can really damage an amplifier that can’t
                                                                                                                                                       Phasing is never absolute in a car audio situa-
Make sure the cap is a polarized electrolytic, 16V or higher, and                                                                                      tions, since speakers are rarely facing the same
remember that the diode introduces a 0.7V drop on the remote wire,                              handle low impedance. Check your specs before          directions. Phasing differences mostly affect bass.
which can cause the processor to power down before the rest of the                              you attempt a Parallel hookup. A Series hookup         Is your system lacking bass? Try changing the
system. There will be a quiz.                                                 +        –        increases impedance, drawing less current from         phase on your sub system. 90% of the time,
                                                                               Amplifier        your amplifier (which is, in turn, less efficient).    that’s the key to more bass!
                                                                               Crossover        But it’s usually easier for an amplifier to handle
                                                                                                speakers in a Series hookup.

                                                                              Series Hookup

                                                                                                                                                      Polk Audio®, The Speaker Specialists®
How do I use my faders and
balance settings to make my
system sound better?
Proper setting of your front-to-rear fader and
left/right balance controls is important for opti-
mum staging and imaging in your system. Too
much sound in the rear of the car (sometimes
called “rear fill”) will often eliminate staging       Can my car stereo really hurt
altogether, forcing sound away from the front of       my ears?
the car, while too little rear fill will sound dull.                                                                                                   Did we miss anything? Do you have a question
Too much sound on one side of the car or the           Sure. Prolonged exposure to sound pressure lev-                                                 or problem or concern that we didn’t cover
other will add an unrealistic element to the           els above 85dB will cause permanent hearing                                                     here? Let me know! Call Polk Audio’s friendly
imaging. To adjust fade and balance, play a tape       damage. Professional audio competitions specify                                                 Customer Service Department. In North America,
or CD you are familiar with and turn the rear          the use of hearing protection devices for their                                                 call (800) 377-7655, Monday through Friday,
speakers on full with the fade control. Listen to      contests, especially at higher volume levels. You                                               9:00am through 6:00pm, EST. Or, email to
the rear speakers, and then slowly turn the fade       can test the dB level of your car stereo with a                                       
up in the front speakers just until you can’t tell     Sound Pressure Level Meter (available at Radio
the rear speakers are playing anymore, then ease       Shack). If you’re disoriented and your hearing is
off a tad. You’re probably close to optimum set-       sort of muffled after you’ve been listening to
ting when the front staging is such that the rear      your car stereo, or you hear ringing in your ears,
speakers provide little more than ambiance and         then turn it down! If you have to shout at the
space to the sound. Test it by going full on the       person in the passenger seat, and you’re not
front speakers (without losing the position you        angry with them, then it’s a good bet that your
just attained). You’ll hear an immediate loss of       stereo is too loud. For the sake of your hearing,
spaciousness in the sound with the rear speakers       turn it down.
faded all the way down. Return to your optimum
setting. Setting the balance is more difficult, so
it’s always a good idea to leave the balance                                                                Bill Flegler, Polk Audio 12v Specialist
fader at the “12 o’clock” position. That’s as close
to equal as you’re going to be able to hear with
your own ears.

                                                                                                            That’s All
                                                                                                               Folks!                                 Polk Audio®, The Speaker Specialists®   23
Polk Audio, Inc.
5601 Metro Dr.
Baltimore, MD 21215
(800) 377-7655


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Description: Car Handbook