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Cordless Speakers

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Speakers
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
               Center cap
                                                               Cone


                                                                                         Edge


                                                                                       Frame


                                                                            Damper


                                                                         Yoke plate




                                                                                                       Speakers
      Voice coil


      Pole piece

                                                                             Yoke
      Magnet

                              Block diagram of cone speaker




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Speakers
    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.



                                                                 3
                                     1
                                                                             6
                           2


                                                                             7




                                                                             8
                           5




                       4




                                                                                                     Speakers
1                                                  5
    Sound passes through the speaker net. The          The printed circuit board contains the
    speaker net also serves to protect the             electrical circuitry.
    speaker cone.
                                                   6
2
    The speaker unit is another name for the       7
    speaker.
3                                                  8
    The cabinet is the speaker's external              This area contains ICs, transistors,
    housing.                                           condensers, resistors, switches, volume
                                                       controls, etc.
4
    The knob is used to adjust the volume. Knob
    functions differ from speaker to speaker.




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Speakers
                                                                Active speakers contain amplifiers which
                          Active speakers                       drive the speakers.

                                                                Passive speakers do not contain speak-
                         Passive speakers
                                                                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.
Features

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.




                                                                                                                       Speakers
Extra functions          These speakers contain electrical
                         circuitry, so it is relatively easy to add
                                                                       It is difficult to add extra functions to
                                                                       these speakers.
(volume, sound quality   extra functions.
control, etc.)




                               Stereo                                        Separate left/right type


                            Monaural                                              Single box type




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Speakers
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.




                       N
                       S

     Magnet




        The leaked magnetic flux affects the television’s cathode ray tube, causing
        discoloration.




                                                                                                          Speakers
                        N
                        S                                                        The magnetic
                                                                                 flux is canceled
                        S                                                        out by an opposing
                        N                                                        magnetic field.


    Canceling magnet


        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.




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                   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.)




                             Transmitter
                          outputting a signal
Speakers




                   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!
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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
speakers.




                                                                                          Speakers
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.



Listening size

                            Up-down mechanism

         Carrying size


Cabinet size can be increased
for listening to music, and
reduced when the speaker is
to be carried.
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Speakers




           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
            much.

            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
            exams.