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JP2007020153

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DESCRIPTION JP2007020153
PROBLEM TO BE SOLVED: To provide a speaker capable of accurately detecting the capacitance
formed between a center pole and a voice coil bobbin without being affected by disturbance
noise. SOLUTION: A speaker 1 detects a capacitance formed between a center pole 5 and a voice
coil bobbin 5 and outputs it as an electric signal, and a conductor layer of the bobbin 10 is a first
conductor layer. 12, the second conductor layer 14, and the third conductor layer 16, and the
first insulator layer 13 between the first conductor layer 12 and the second conductor layer 14;
A second insulator layer 15 is interposed between the body layer 14 and the third conductor
layer 16. Since the capacitor 27 composed of the center pole 6 and the first conductor layer 12
and the capacitor 28 composed of the first conductor layer 12 and the second conductor layer
14 are connected in parallel, The capacitance to be detected can be made less susceptible to
disturbance noise. [Selected figure] Figure 2
スピーカー
[0001]
The present invention relates to a speaker, and more particularly to a speaker for detecting an
operating state of a diaphragm.
[0002]
A speaker equipped with an MFB (Motional Feed Back) circuit is known as a technology for
improving the sound quality of the speaker.
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1
The MFB circuit detects the operating state of the vibrating diaphragm based on an electrical
signal (hereinafter referred to as "audio signal") indicating audio information input to the
speaker, and feeds back the diaphragm based on the detection result. It is controlled, and this
makes it possible to eliminate the distortion of the sound that is likely to occur particularly in the
low tone range. Therefore, it is generally considered that the MFB circuit is effectively employed
in a small speaker which is considered to be difficult to reproduce in the low frequency range.
[0003]
For example, Patent Documents 1 to 5 are disclosed as the technology related to the MFB circuit.
In each of Patent Documents 1 to 5, the operation state of the diaphragm is detected by detecting
a change in capacitance formed between the electrodes. Specifically, an electrode (hereinafter
referred to as a "movable electrode") is fixed to a diaphragm or an electromagnetic coil called a
voice coil bobbin for vibrating the diaphragm, and the electrode is opposed to the movable
electrode. (Hereinafter, referred to as "fixed electrode") is fixed, the electrostatic capacitance
changed by the movable electrode moving relative to the fixed electrode is detected by the
detector, and this is converted by the conversion circuit (electrical signal ( Hereinafter, the signal
is converted into detection signal and output. Then, the detection signal and the audio signal
are compared by a comparison device (for example, CPU), and the operation of the diaphragm is
appropriately made based on the comparison result, that is, the difference between the output
level of the detection signal and the output level of the audio signal. Control. JP-A-52-79,644 JPA-53-12319, JP-A-53-12320, JP-A-53-12,221, JP-A-57-96589
[0004]
However, since the electrostatic capacitance formed between the electrodes is very small, such as
several pF to several hundreds pF, it fluctuates under the influence of noise such as a slight
amount of electromagnetic waves or static electricity. For example, the diaphragm is generally
configured to vibrate by an excitation action by a voice coil bobbin, an iron core called a center
pole fitted to the voice coil bobbin, and a magnet generating a magnetic flux penetrating the
voice coil bobbin and the center pole. However, the capacitance between the electrodes
fluctuates under the influence of the excitation current flowing through the voice coil bobbin. In
addition, some electronic components incorporated in a speaker may emit electromagnetic waves
although they are weak, and the electromagnetic waves may propagate to the electrodes, which
may cause fluctuations in capacitance. In addition, the capacitance between the electrodes is set
by friction caused by mechanical phenomena such as vibration of parts incorporated in the
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2
speaker, static electricity caused by various electromagnetic phenomena inside and outside the
speaker, and around the speaker It is also conceivable to receive the influence of an
electromagnetic wave or the like (hereinafter referred to as disturbance noise ) output from
an electronic device that is present. As described above, in the techniques of Patent Documents 1
to 5, there is a problem that the capacitance fluctuates and it becomes impossible to detect the
correct capacitance formed between the electrodes.
[0005]
The present invention has been made to solve the above-described problems, and it is an object
of the present invention to provide a speaker capable of accurately detecting the capacitance
formed between electrodes without being affected by disturbance noise. I assume.
[0006]
In order to achieve such an object, a speaker according to the present invention detects a
capacitance formed between a center pole and a voice coil bobbin having a bobbin consisting of
an insulator layer and a nonmagnetic conductor layer. It is characterized in that the conductor
layer of the bobbin is constituted by three or more, and the insulator layer is interposed between
the conductor layers.
[0007]
Therefore, according to this speaker, it is configured between the center pole and the first
conductor layer facing the center pole (of the conductor layers, the conductor layer with the
shortest distance to the center pole). The second conductive layer (the conductive layer adjacent
to the first conductive layer of the conductive layers) and the capacitor formed between the first
conductive layer in parallel Capacitance formed between the center pole and the first conductor
layer, and capacitance formed between the first conductor layer and the second conductor layer.
Can be detected.
That is, a capacitance larger than the capacitance formed between the center pole and one
conductor layer can be obtained, and the influence of disturbance noise can be reduced.
In addition, the conductor layers other than the first and second conductor layers function as a
shield that shields disturbance noise. As a result, it is possible to detect the true capacitance
without disturbance noise. Furthermore, by interposing the insulator layer between the
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3
conductor layers, the relative dielectric constant is increased and the capacitance is increased, so
the influence of disturbance noise can be further reduced. Specifically, the conductive layer is
composed of three from the side of the center pole, the first conductive layer, the second
conductive layer, and the third conductive layer, and the center pole and the third conductive
layer are A first capacitor is formed of the first conductive layer, and a second capacitor is
formed of the first conductive layer and the second conductive layer, and the first capacitor and
the second capacitor are formed. Are connected in parallel, and the sum of the capacitance of the
first capacitor and the capacitance of the second capacitor may be output as the electric signal.
[0008]
In the above-described speaker, among the conductor layers, the conductor layers other than the
conductor layer having the shortest distance to the center pole may be grounded. In this case, the
capacitance formed between the center pole and the first conductor layer described above, and
the electrostatic capacitance formed between the first conductor layer and the second conductor
layer The total amount with the capacity can be increased. That is, by grounding the second
conductive layer, the capacitance formed between the first conductive layer and the second
conductive layer can be increased. This will increase the overall capacitance. Further, the
shielding effect of the conductor layers other than the first and second conductor layers can be
enhanced.
[0009]
In the speaker according to the invention, the conductor layer having the longest distance to the
center pole among the conductor layers is grounded, and the conductor layer having the shortest
distance to the center pole among the conductor layers, and the center An electrical signal can be
input to the conductor layer between the conductor layer and the conductor layer having the
longest distance to the pole. In this case, the intermediate conductor layer (the conductor layer
positioned between the first conductor layer and the conductor layer having the longest distance
to the center pole among the conductor layers) is a so-called boot strap. It functions as an
electrode, and it becomes possible to constitute a pure capacitor with the center pole and the
voice coil bobbin. For example, after converting the capacitance formed between the center pole
and the first conductive layer into an electrical signal, the electrical signal is fed back to the
intermediate conductive layer to increase the impedance of the bobbin. Thus, the center pole and
the voice coil bobbin can constitute a capacitor that is less susceptible to disturbance noise.
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[0010]
As described above, according to the speaker of the present invention, the conductor layer of the
bobbin is composed of three or more, and the insulator layer is interposed between the
conductor layers, and the center pole and the center pole of the conductor layers are the center
pole. Between the conductor layer and the conductor layer, and the conductor layer of the
conductor layer having the shortest distance to the center pole, and the conductor adjacent to the
conductor layer The sum of the capacitance formed with the body layer is detected, and the
conductor layer having the shortest distance to the center pole among the conductor layers, and
the conductor adjacent to the conductor layer are detected. Since the disturbance noise is
blocked by the conductor layer other than the body layer, the true capacitance can be detected
without being affected by the disturbance noise. Therefore, since the reliability of the detection
result is increased, for example, the detection result can be effectively used for the MFB circuit,
and the distortion of the sound emitted from the speaker, which is a conventional problem, can
be eliminated. This makes it possible to realize a bass range comparable to a large speaker even
with a small speaker.
[0011]
In the present invention, if the conductor layers other than the conductor layer having the
shortest distance to the center pole among the conductor layers are grounded, the center pole
and the center pole of the conductor layers can be separated. The capacitance formed between
the conductor layer having the shortest distance, the conductor layer having the shortest
distance to the center pole among the conductor layers, and the conductor layer adjacent to the
conductor layer And the total amount with the capacitance formed between Further, among the
conductor layers, the shielding effect of the conductor layer having the shortest distance to the
center pole and the conductor layers other than the conductor layer adjacent to the conductor
layer can be enhanced. Thus, true capacitance can be detected without being affected by
disturbance noise. Therefore, since the reliability of the detection result is further enhanced, for
example, the detection result can be effectively used for the MFB circuit, and the distortion of the
sound emitted from the speaker, which has been a problem in the prior art, can be eliminated .
This makes it possible to realize a bass range comparable to a large speaker even with a small
speaker.
[0012]
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In the present invention, of the conductor layers, the conductor layer having the longest distance
to the center pole is grounded, and the conductor layer having the shortest distance to the center
pole is the conductor layer, and the center pole and the conductor layer. If an electrical signal is
input to the conductor layer between the conductor layer and the conductor layer with the
longest distance, the conductor layer with the shortest distance to the center pole and the center
pole A conductor layer located between the conductor layer with the longest distance can be
made to function as a so-called bootstrap electrode, the impedance of the bobbin can be
increased, and a capacitor that is less susceptible to disturbance noise between the center pole
and the voice coil bobbin It can be configured. Therefore, since the reliability of the capacitance
detected by the capacitor is further enhanced, for example, the detection result can be effectively
used for the MFB circuit, and the sound emitted from the conventional speaker is Distortion can
be eliminated. This makes it possible to realize a bass range comparable to a large speaker even
with a small speaker.
[0013]
Hereinafter, the configuration of the present invention will be described in detail based on the
best mode shown in the drawings.
[0014]
One Embodiment of the speaker of this invention is shown in FIGS. 1-3.
The speaker 1 of the present invention detects the capacitance formed between the center pole 5
and the voice coil bobbin 4 having the bobbin 10 consisting of the insulator layer and the
nonmagnetic conductor layer, and outputs it as an electric signal. The conductor layer of the
bobbin 10 is composed of the first conductor layer 12, the second conductor layer 14, and the
third conductor layer 16 (consisting of three or more conductor layers of the bobbin 10 And the
first insulating layer 13 between the first conductive layer 12 and the second conductive layer
14, and the second insulating layer between the second conductive layer 14 and the third
conductive layer 16. It is characterized in that the body layer 15 is interposed (the insulator layer
is interposed between the conductor layers).
[0015]
As shown in FIG. 1, the speaker 1 includes diaphragms 2 and 3, a voice coil bobbin 4, a center
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pole 5, magnets 6 and 7, and a yoke 8. Case 9 is formed in a bowl shape. In addition to the center
pole 5, magnets 6, 7 and a yoke 8 are accommodated in the case 9, and they are fixed to the
inner wall surface of the case 9 with an adhesive or a screw. The center pole 5 is made of iron,
and includes a cylindrical center pole body 5a and a disk-like flange 5b formed at the base end of
the center pole body 5a. The center pole 5 is disposed in the case 9 such that the tip end portion
of the center pole body 5 a protrudes from the approximate center of the opening 9 a of the case
9 to the outside of the case 9.
[0016]
The center pole 5 and the case 9 are connected to a housing (not shown) called an enclosure and
grounded. A ring-shaped magnet 6 centered on the center pole body 5a is magnetically attracted
to the surface of the flange 5b facing the opening 9a. A substantially disc-like yoke 8 is
magnetically attracted to the surface of the magnet 6 facing the opening 9a, and the magnet 6 is
sandwiched between the yoke 8 and the flange 5b. A ring-shaped magnet 7 having the same
shape as the magnet 6 is disposed between the surface of the flange 5b facing the bottom 9b of
the case 9 and the bottom 9b. The magnet 7 is disposed at the bottom 9 b such that the pole on
the side contacting the flange 5 b is the same as the pole on the side contacting the flange 5 b of
the magnet 6. As a result, a stable magnetic flux loop (described later) is formed between the
magnet 6, the yoke 8 and the center pole 5.
[0017]
The substantially disc-shaped yoke 8 is substantially orthogonal to the longitudinal axis of the
cylindrical center pole body 5a, and the magnet 6 is arranged such that the inner circumferential
surface thereof faces the outer circumferential surface 5d of the center pole body 5a. The air gap
is formed between the inner peripheral surface of the yoke 8 and the outer peripheral surface 5d
of the center pole body 5a. Further, in the case 9, the substantially disk-shaped yoke 8 is in close
proximity with the inner peripheral surface facing the center pole main body 5 a and the outer
peripheral surface facing the inner wall surface of the case 9. It is arranged as.
[0018]
The voice coil bobbin 4 is composed of a cylindrical bobbin 10 having an open front end and a
rear end, and a coil 11 wound around the outer periphery of the bobbin 10. As the coil 11, a
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conductor such as an enameled wire or a copper wire may be used, and it may be determined
appropriately. As shown in FIG. 2, the bobbin 10 is composed of a first conductor layer 12, a first
insulator layer 13, a second conductor layer 14, a second insulator layer 15, and a third
conductor layer 16. There is. The first conductor layer 12, the second conductor layer 14, and
the third conductor layer 16 are copper foils, and the first insulator layer 13 and the second
insulator layer 15 are polyimide films. The bobbin 10 is laminated in order of the first conductor
layer 12, the first insulator layer 13, the second conductor layer 14, the second insulator layer
15, and the third conductor layer 16 from the inside to the outside thereof. . Although not
particularly illustrated, an insulating film is formed between the coil 11 and the third conductor
16 by coating treatment, and the coil 11 and the third conductor 16 are in an electrically
insulated state. . The terminal 17 connected to the first conductor layer 12 via a lead is
connected to the non-inverted input terminal (see FIG. 4) of the operational amplifier 25a of the
conversion circuit 25 described later. The second and third conductor layers 14 and 16 are
connected to the frame 18 (see FIG. 1) and grounded.
[0019]
As shown in FIG. 1, the bobbin 10 is attached to the case 9 so as to be slidable in the front-rear
direction (the direction of the arrow A in FIG. 1). . The inner diameter of the bobbin 10 is slightly
larger than the outer diameter of the center pole body 5a, and the bobbin 10 is placed on the
center pole body 5a. That is, the coil 11 is opposed to one end face of the yoke 8, and the bobbin
10 is covered on the center pole main body 5a so that the outer peripheral surface 5c of the
center pole main body 5a and the inner peripheral surface of the bobbin 10 become substantially
parallel. As a result, one end face of the yoke 8 comes close to the coil 11, and the inner
peripheral surface of the bobbin 10 comes close to the outer peripheral surface 5c of the center
pole main body 5a. A constant magnetic flux loop is always formed in the direction of the arc
arrow in the figure. The magnet 6 and the yoke 8 may be installed at a place where a constant
magnetic flux can be formed between the center pole 5, the magnet 6 and the yoke 8, and the
installation place may be appropriately determined. good.
[0020]
A frame 18 is bonded to the surface of the yoke 8 exposed to the outside of the case 9 with an
adhesive. The frame 18 is bonded to the above-described housing (not shown) with a screw or an
adhesive and is grounded. The diaphragms 2 and 3 are attached to the bobbin 10. The
diaphragm 2 is a thin plate having a plurality of bent portions, one end of which is bonded to the
outer peripheral surface of the bobbin 10 and the other end of which is bonded to the frame 18
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8
with an adhesive. The diaphragm 3 functions as so-called cone paper, and one end thereof is
joined to the outer peripheral surface of the bobbin 10 and the other end is connected to the
frame 18 through a joint 19. The center cap 20 is made of aluminum or the like, and comprises a
dome-shaped main body and a ridge formed along the outer peripheral edge of the main body,
and the ridge is joined to the diaphragm 3 with an adhesive. ing. Thus, the opening 10 a of the
bobbin 10 is covered by the center cap 20.
[0021]
As shown in FIG. 3, an electrical signal (hereinafter referred to as audio signal ) indicating
audio information input to the input terminal 21 is input to the power amplifier 23 through the
comparator 22 composed of a CPU (Central Processing Unit). Be done. The voice signal amplified
by the power amplifier 23 is input to the voice coil bobbin 4. That is, a current indicating a voice
signal flows through the coil 11 of the voice coil bobbin 4, and the voice coil bobbin 4 is moved
in the front-rear direction by the excitation action of this current and the magnetic flux formed
between the center pole 5, the magnet 6, and the yoke 8. It vibrates in the direction of arrow A
shown in FIG. Along with this, the diaphragms 2 and 3 also vibrate and sound is emitted from the
speaker 1.
[0022]
The speaker 1 is provided with a detector 24, a conversion circuit 25, and a feedback circuit 26.
Although described later in detail, the detector 24 is configured of a first capacitor 27 and a
second capacitor 28 (see FIG. 4). As shown in FIG. 4, the conversion circuit 25 includes an
operational amplifier 25a, a power supply 25b, and a transistor 25c. The non-inverted input
terminal of the operational amplifier 25a and the first conductive layer 12 of the voice coil
bobbin 4 are connected via a lead wire. A bias voltage is applied to the non-inverting input
terminal of the operational amplifier 25a and the first conductive layer 12 by the power supply
25b. The output terminal of the operational amplifier 25a is connected to the input terminal of
the transistor 25c, whereby the signal output from the output terminal of the operational
amplifier 25a is input to the input terminal of the transistor 25c. The emitter serving as the
negative output terminal of the transistor 25c is connected to the inverting input terminal of the
operational amplifier 25a, and the emitter of the transistor 25c and the inverting input terminal
of the operational amplifier 25a are connected to the center pole 5. It is grounded. Although not
particularly shown, the feedback circuit 26 is composed of an integration circuit, a buffer
amplifier, an electronic volume, an adder circuit, and the like.
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[0023]
The first capacitor 27 is composed of the center pole 5 and the first conductor layer 12. The
second capacitor 28 is composed of the first conductor layer 12 and the second conductor layer
14. As described above, by connecting the non-inverting input terminal of the operational
amplifier 25a to the first conductive layer 12 of the voice coil bobbin 4, the capacitor 27 and the
capacitor 28 are connected in parallel, and the capacitor 27 is formed. The electrostatic
capacitance, which is the sum of the electrostatic capacitance and the electrostatic capacitance
formed by the capacitor 28, is input to the operational amplifier 25a of the conversion circuit 25
as an electric signal. The electric signal input from the detector 24 in this manner is subjected to
CV conversion (electrostatic capacitance-voltage conversion) and amplification by the operational
amplifier 25a and the transistor 25c, and compared as a detection signal from the terminal 25d
via the feedback circuit 26. The signal is input to the The comparator 22 responds to the input
detection signal and compares the audio signal input from the input terminal 21 with the
detection signal. Then, the comparison result, that is, the output level of the audio signal and the
output level of the detection signal are compared, and the difference is calculated. Then, the
power amplifier 23 adjusts the output level of the audio signal based on the calculation result
and inputs it to the voice coil bobbin 4. Then, the voice coil bobbin 4 vibrates based on the audio
signal input from the power amplifier 23.
[0024]
As described above, according to the speaker 1 having the structure shown in FIGS. 1 to 4, when
an audio signal is input to the input terminal 21, the voice coil bobbin 4 vibrates based on the
audio signal, and this vibration causes vibration. Plates 2 and 3 vibrate. The vibration of these
diaphragms causes the speaker 1 to generate sound. The operating state of the diaphragms 2
and 3 at this time is recognized by detecting the capacitance with the detector 4. That is, the
facing area of the first conductive layer 12 of the voice coil bobbin 4 and the outer peripheral
surface 5c of the center pole body 5a changes, and the sum of the capacitance formed by the
capacitor 27 and the capacitance formed by the capacitor 28 Changes. The change of the sum
corresponds to the displacement of the diaphragms 2 and 3. Thus, an electrical signal indicating
the capacitance detected by the detector 24 is input to the conversion circuit 25. Then, in the
conversion circuit 25, an electric signal indicating capacitance is converted to a detection signal,
and the detection signal is input to the comparator 22 via the feedback circuit 26. The
comparator 22 compares the detection signal with the audio signal, and inputs the comparison
result to the power amplifier 23 together with the audio signal. The power amplifier 23 adjusts
the audio signal based on the comparison result and inputs it to the voice coil bobbin 4.
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10
[0025]
In the present invention, the bobbin 10 is formed of the first conductor layer 12, the first
insulator layer 13, the second conductor layer 14, the second insulator layer 15, and the third
conductor layer 16, and the center pole 5 is formed. Because the capacitor 27 formed of the first
and second conductive layers 12 and the capacitor 28 formed of the first and second conductive
layers 12 and 14 are connected in parallel, the center pole 5 is Compared to the conventional
mode in which only the electrostatic capacitance formed between the first conductor layer 12
and the first conductive layer 12 is detected, the electrostatic capacitance to be detected is larger,
so that it is not affected by the disturbance noise. Capacitance can be detected. Further, since the
second conductor layer 14 and the third conductor layer 16 are electrically insulated by the
second insulator layer 15 and the third conductor layer 16 is grounded, the disturbance noise is
blocked. be able to. Furthermore, since the first insulator layer 13 is interposed between the first
conductor layer 12 and the second conductor layer 14, the relative permittivity of the capacitor
27 can be increased, and the capacitance is increased. Can.
[0026]
Next, a second embodiment of the present invention will be described with reference to FIGS. 5
and 6. In addition, about the structural member similar to 1st Embodiment, the same code ¦
symbol is attached ¦ subjected to drawing and description is abbreviate ¦ omitted.
[0027]
A terminal 29 is connected to the second conductive layer 14 of the bobbin 10 via a lead wire.
This terminal 29 is connected to the inverting input terminal of the operational amplifier 25a and
to the emitter which is the negative output terminal of the transistor 25c. Thus, the detection
signal output from the conversion circuit 25 is input to the feedback circuit 26 (see FIG. 3) and to
the second conductor layer 14. In this manner, the detection signal is input to the second
conductor layer 14 to increase the impedance of the second conductor layer 14 and the second
conductor layer 14 functions as a so-called bootstrap electrode. The pole 5 and the first
conductor layer 12 can constitute a capacitor that is less susceptible to disturbance noise.
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11
[0028]
The above-described embodiment is an example of the preferred embodiment of the present
invention, but is not limited to this, and various modifications can be made without departing
from the scope of the present invention. In the above embodiment, the bobbin 10 is constituted
by three conductor layers of the first conductor layer 12, the second conductor layer 14, and the
third conductor layer 16 and an insulator layer interposed between conductor layers. However,
the present invention is not limited to this. For example, four or more conductive layers and an
insulator layer interposed between these conductive layers may be used. At this time, the
conductive layers other than the conductive layer having the shortest distance to the center pole
5 are grounded. In this case, the conductor layers other than the conductor layer having the
shortest distance to the center pole 5 function as a shield for blocking disturbance noise. Further,
the conductor layer having the shortest distance to the center pole 5 and the conductor layers
other than the conductor layer adjacent to the conductor layer are grounded, and the distance
between the center pole 5 and the center pole 5 is Connect in parallel the capacitor composed of
the shortest conductor layer and the capacitor composed of the conductor layer shortest in
distance to the center pole 5 and the conductor layer adjacent to this conductor layer You may
do so. Thus, disturbance noise can be cut off more reliably, and a capacitance that is less
susceptible to the influence of disturbance noise can be formed.
[0029]
Although the first conductive layer 12, the second conductive layer 14, and the third conductive
layer 16 are formed of copper foil in the above embodiment, they may be formed of aluminum,
conductive plastic, or the like. Any non-magnetic conductor can be appropriately changed.
Moreover, although the 1st and 2nd insulator layers 13 and 15 were formed with the polyimide,
for example, these may be formed with paper and if it is an insulator, it can change suitably.
[0030]
It is sectional drawing which shows the structure of the speaker of this invention. It is a sectional
view showing a voice coil bobbin, a center pole, and a part of yoke. It is a functional block
diagram which shows the electric constitution of a speaker. It is a circuit diagram showing
composition of a detector and a conversion circuit. It is a sectional view showing a part of voice
coil bobbin, center pole, and yoke in a 2nd embodiment of the present invention. It is a circuit
diagram showing composition of a detector in a 2nd embodiment of the present invention, and a
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conversion circuit.
Explanation of sign
[0031]
DESCRIPTION OF SYMBOLS 1 Speaker 4 voice coil bobbin 5 center pole 10 bobbin 12 1st
conductor layer 13 1st insulator layer 14 2nd conductor layer 15 2nd insulator layer 16 3rd
conductor layer 22 comparator 24 detector 25 conversion circuit
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