As shown below, the basic principles behind speakers are the same as for headphones. Current
passing through a voice coil generates a magnetic field, drawing the coil towards the magnet
located beneath it or pushing it in the opposite direction. This causes the cone to vibrate, and
the cone vibrations are transmitted to air, thereby forming sound.
Lead wire Gasket
Block diagram of cone speaker
The diagram below is a cross section of the internal structure of the most popular type of
speaker available on the market today. The asterisks denote parts that are unique to
active speakers. These parts are not found in passive speakers.
Sound passes through the speaker net. The The printed circuit board contains the
speaker net also serves to protect the electrical circuitry.
The speaker unit is another name for the 7
The cabinet is the speaker's external This area contains ICs, transistors,
housing. condensers, resistors, switches, volume
The knob is used to adjust the volume. Knob
functions differ from speaker to speaker.
Active speakers contain amplifiers which
Active speakers drive the speakers.
Passive speakers do not contain speak-
er-driving amplifiers. Instead, they are
driven directly by the output of the con-
nected equipment. The AV accessory
speakers referred to here are low-priced
speakers costing less than 10,000 yen.
High-end speakers, such as high-fidelity
speakers, are not included.
Contains an amplifier to drive the Does not contain an amplifier. The
speaker. speaker is directly driven by the output
of the connected equipment.
Price Expensive Cheap
Power supply Required Not required
These speakers contain special The output of these speakers depends
amplifiers which provide stable power on the output of the connected
independent of the output of the equipment. If the speakers are
Output connected audio equipment. connected to a headphone jack, high-
volume output cannot be expected.
Extra functions These speakers contain electrical
circuitry, so it is relatively easy to add
It is difficult to add extra functions to
(volume, sound quality extra functions.
Stereo Separate left/right type
Monaural Single box type
Speakers contain powerful magnets, the magnetic force of which may leak outside the
speaker cabinet. When speakers are placed close to a television or PC, this magnetic
force may have adverse effects, such as causing cathode ray tube discoloration. To
prevent such problems, magnetically shielded speakers are designed so that the magnetic
force of speaker magnets does not leak to the exterior.
The leaked magnetic flux affects the television’s cathode ray tube, causing
S The magnetic
flux is canceled
S out by an opposing
N magnetic field.
The canceling magnet creates an opposing magnetic field that cancels out
and eliminates the leaked magnetic flux. This prevents the cathode ray
tube from being affected.
With cordless speakers, the speaker box contains a receiver, which receives a
transmitted infrared signal and converts it to sound. Because there are no cords,
cordless speakers can be placed wherever you like. (Their operations are based
on the same principles as those of cordless headphones.)
outputting a signal
The direct position function allows active speakers to be used as passive
speakers even if their batteries die. Passive output from active speakers using
this function is not as powerful as battery-powered active speaker output, but
the function is useful as an energy-saving function when listeners want to listen
at low volume (e.g., at night), or when they want to use their speakers but the
batteries are dead.
Direct position lets you use active speakers as passive speakers,
even when the batteries die!
As a basic rule, most stereo speakers are independent left and right speakers
(except for single box speakers). The joint mechanism lets you join the left and
right speakers together for easy carrying. This feature makes it easy to move
Because of the way speakers are designed, as cabinet size increases, listeners
are better able to sense the spread of low-range sounds. Unfortunately, small-
sized speakers cannot be increased in size without affecting their portability. To
address this issue, Panasonic employs a proprietary function called an up-down
mechanism in model number RP-SP19AE.
Cabinet size can be increased
for listening to music, and
reduced when the speaker is
to be carried.
In the past, small-sized speakers were typically used in combination with
equipment such as a headphone stereo. Now cordless speakers let users take
advantage of the freedom of being cordless. Here are some examples of
applications where cordless speakers are very useful.
As elderly listeners become hard of hearing, they often need to turn up the
volume on the television, etc. in order to hear it properly. With cordless speakers,
they can keep the speakers nearby, so they don't need to turn up the volume as
When you come home late at night and it is very quiet, you may not be able to
turn up the television volume to the level you like. Cordless speakers give you
flexibility since you can easily place them close to where you are sitting.
Cordless speakers are a great convenience when you want to watch television or
listen to the radio without disturbing your children while they are studying for