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JP2012023559

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DESCRIPTION JP2012023559
An electrostatic speaker is provided to prevent an electric shock and to prevent a decrease in
insulation. SOLUTION: Electrodes 20U and 20L are located on both sides of a vibrating body 10,
and spacers 40U and 40L which are non-woven fabrics are located outside the electrodes 20U
and 20L. The covers 50U and 50L in which a metal conductive film is formed on the entire
surface of the insulating synthetic resin film are located outside the spacers 40U and 40L. The
cover 50U and the cover 50L are electrically connected and connected to the ground GND of a
drive circuit that supplies an acoustic signal to the electrodes 20U and 20L. [Selected figure]
Figure 4
Electrostatic speaker
[0001]
The present invention relates to an electrostatic speaker.
[0002]
The condenser type headphone disclosed in Patent Document 1 has a configuration in which a
diaphragm is sandwiched by fixed electrodes.
Electrode foils are formed on both sides of the fixed electrode, and the electrode foil on the front
surface and the electrode foil on the back surface are nonconductive. In addition, a plurality of
holes are provided in the fixed pole. At the fixed pole, the electrode foil located on the ear side of
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the user is connected to the ground.
[0003]
JP, 2006-270663, A
[0004]
According to the headphone disclosed in Patent Document 1, since the electrode foil located on
the ear side of the human body is grounded, there is no risk of electric shock even if the ear
approaches the electrode foil located on the ear side of the human body .
However, since the fixed pole is provided with a hole, there is a possibility that liquid such as
sweat may enter the inside of the headphone from the hole and the insulation property may be
reduced.
[0005]
The present invention has been made under the above-described background, and an object of
the present invention is to provide a technique for preventing an electric shock and preventing a
reduction in insulation in an electrostatic speaker.
[0006]
In order to solve the problems described above, the present invention provides a vibrator having
conductivity, a pair of electrodes opposed to each other with the vibrator interposed
therebetween, and spaced from the vibrator, and waterproof and insulating properties. And a
conductive film formed on the entire surface of at least one surface of the film, and a pair of
covers facing each other across the vibrator and the pair of electrodes, the pair of covers, and the
pair of electrodes And a pair of spacers, each having an insulating property and allowing sound
to pass therethrough, the pair of covers being electrically connected to each other, the first
acoustic signal being transmitted to one of the pair of electrodes. An electrostatic speaker is
provided, which is connected to the ground of a drive circuit that supplies and supplies a second
acoustic signal whose polarity is reversed to the first acoustic signal to the other of the pair of
electrodes.
[0007]
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In the present invention, the edges of the pair of covers may be fixed, and the vibrator and the
pair of electrodes may be positioned in the space between the pair of covers.
Further, in the present invention, the drive circuit has an amplifier circuit for amplifying an input
signal, and the first acoustic signal is generated by amplifying an acoustic signal input to the
amplifier circuit in phase with the amplifier circuit The second acoustic signal is a signal obtained
by amplifying the acoustic signal input to the amplifier circuit in the amplifier circuit with the
opposite polarity to the acoustic signal, and one terminal of the primary side The acoustic signal
is input to the other terminal of the primary side is grounded, one terminal of the secondary side
is connected to the amplification circuit, and the other terminal of the secondary side is
connected to the ground of the drive circuit It may be configured to have the isolated
transformer.
[0008]
According to the present invention, in the electrostatic speaker, it is possible to prevent an
electric shock and to prevent a decrease in insulation.
[0009]
FIG. 1 is an external view of an electrostatic speaker according to an embodiment of the present
invention.
1. AA sectional view taken on the line of FIG.
The exploded view of electrostatic type speaker 1. FIG. 2 is a diagram showing an electrical
configuration according to the electrostatic speaker 1. The exploded view of electrostatic type
speaker 1 concerning a modification. The figure which showed the electric constitution of the
drive circuit 100 which concerns on a modification. The figure which showed the electric
constitution of the drive circuit 100 which concerns on a modification.
[0010]
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Embodiment FIG. 1 is an external view of an electrostatic speaker 1 according to an embodiment
of the present invention, and FIG. 2 is a cross-sectional view of the electrostatic speaker 1 taken
along line AA. 3 is an exploded view of the electrostatic speaker 1, and FIG. 4 is a diagram
showing the electrical configuration of the electrostatic speaker 1. As shown in FIG. In the figure,
the directions are indicated by the orthogonal X-axis, Y-axis, and Z-axis, and the horizontal
direction when the electrostatic speaker 1 is viewed from the front is the X-axis direction, and the
depth direction is the Y-axis direction. The height direction is the direction of the Z axis. Further,
in the drawings, those in which • is described in o means an arrow directed from the
back to the front of the drawing. Further, in the drawings, those in which x is described in
o means an arrow directed from the front to the back of the drawing.
[0011]
As shown in the figure, the electrostatic loudspeaker 1 has a vibrator 10, electrodes 20U and
20L, elastic members 30U and 30L, spacers 40U and 40L, covers 50U and 50L, and protection
members 60U and 60L. In the present embodiment, the configurations of the electrode 20U and
the electrode 20L are the same, and the configurations of the elastic member 30U and the elastic
member 30L are the same. Therefore, when there is no particular need to distinguish between
the two in these members, the descriptions such as "L" and "U" are omitted. The configurations of
the spacer 40U and the spacer 40L are the same, the configurations of the cover 50U and the
cover 50L are the same, and the configurations of the protective member 60U and the protective
member 60L are the same. For this reason, also in these members, when it is not necessary to
distinguish between the two, the description of "L", "U", etc. is omitted. Also, the dimensions of
the respective components such as the vibrator and electrodes in the drawing are different from
the actual dimensions so that the shapes of the components can be easily understood.
[0012]
(Configuration of Each Part of Electrostatic Speaker 1) First, each part of the electrostatic speaker
1 will be described. The rectangular vibrating body 10 viewed from the point on the Z axis is
made of a film (insulating layer) of an insulating and flexible synthetic resin such as PET
(polyethylene terephthalate) or PP (polypropylene). A conductive metal is deposited on one
surface of the film to form a conductive film (conductive layer). In the present embodiment, the
conductive film is formed on one side of the film, but may be formed on both sides of the film.
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[0013]
The elastic member 30 is a non-woven fabric in this embodiment and can pass air and sound
without passing electricity, and its shape is rectangular when viewed from a point on the Z axis.
Also, the elastic member 30 has elasticity, and deforms when an external force is applied, and
returns to its original shape when an external force is removed. The elastic member 30 may be a
member having insulation, sound transmission, and elasticity, and it may be formed by applying
heat to the batt and compressing it, woven cloth, and synthetic resin having insulation. Or the
like. In the present embodiment, the length of the elastic member 30 in the X-axis direction is
longer than the length of the vibrating body 10 in the X-axis direction, and the length of the
elastic member 30 in the Y-axis direction is the vibrating body 10 in the Y-axis direction. It is
longer than the length.
[0014]
The spacer 40 is a non-woven fabric in this embodiment and can pass air and sound without
passing electricity, and its shape is rectangular as viewed from the point on the Z axis. Also, the
elastic member 30 has elasticity. In the present embodiment, the spacer 40 is made of the same
material as the elastic member 30. However, the spacer 40 may not be electrically conductive
and may not have elasticity as long as air and sound can pass therethrough. Further, in the
present embodiment, the spacer 40 has the same length in the X-axis direction and the length in
the Y-axis direction as the elastic member 30.
[0015]
The electrode 20 uses a film (insulating layer) of insulating synthetic resin such as PET or PP as a
substrate, and a conductive metal is deposited on one surface of the film to form a conductive
film (conductive layer). It is a structure. The electrode 20 is rectangular when viewed from the
point on the Z-axis, and has a plurality of holes penetrating from the front surface to the back
surface, which allows air and sound to pass therethrough. In the drawings, the illustration of the
holes is omitted. In the present embodiment, the length in the X-axis direction of the electrode 20
and the length in the Y-axis direction are the same as those of the elastic member 30.
[0016]
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The cover 50 uses a film (insulating layer) of insulating synthetic resin such as PET or PP as a
base material, and a conductive metal (for example, aluminum) is deposited on the entire surface
of one of the insulating layers to form a conductive film (conductive). Layer) is formed. In the
present embodiment, the length in the X-axis direction and the length in the Y-axis direction of
the cover 50 are the same as those of the elastic member 30. The insulating layer of the cover 50
is preferably waterproof and has low moisture permeability and low air permeability. In the
present embodiment, the conductive film is formed on one surface of the cover 50, but may be
formed on both surfaces of the cover 50. The protective member 60 is a cloth having an
insulating property. The protective member 60 is rectangular when viewed from a point on the
Z-axis, and allows passage of air and sound. In the present embodiment, the length in the X axis
direction of the protective member 60 and the length in the Y axis direction are the same as
those of the elastic member 30.
[0017]
(Structure of Electrostatic Speaker 1) Next, the structure of the electrostatic speaker 1 will be
described. In the electrostatic loudspeaker 1, the vibrating body 10 is disposed between the
lower surface of the elastic member 30U and the upper surface of the elastic member 30L. The
adhesive is applied to the elastic member 30U and the elastic member 30L with a width of
several mm from the edge in the left-right direction and the edge in the depth direction, and the
portion to which the adhesive is applied The inner side is not fixed to the elastic member 30U
and the elastic member 30L.
[0018]
The electrode 20U is bonded to the upper surface of the elastic member 30U. The electrode 20L
is bonded to the lower surface of the elastic member 30L. The electrode 20U is coated with an
adhesive with a width of several mm from the edge in the left-right direction and the edge in the
depth direction and is adhered to the elastic member 30U, and the electrode 20L has the edge in
the left-right direction and the depth direction An adhesive is applied with a width of several mm
from the edge to the inside and adhered to the elastic member 30L. The electrode 20 is not fixed
to the elastic member 30 on the inner side of the portion to which the adhesive is applied. The
electrode 20U is in contact with the elastic member 30U at the side with the conductive film, and
the electrode 20L is in contact with the elastic member 30L at the side with the conductive film.
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[0019]
The spacer 40U is bonded to the top surface of the electrode 20U. The spacer 40L is bonded to
the lower surface of the electrode 20L. The spacer 40U is coated with an adhesive with a width
of several mm from the edge in the lateral direction and the edge in the depth direction and is
adhered to the electrode 20U, and the spacer 40L has the edge in the lateral direction and the
edge in the depth direction An adhesive is applied in a width of several mm from the inside to
adhere to the electrode 20L. The spacer 40 is in a state where it is not fixed to the electrode 20
inside the portion to which the adhesive is applied.
[0020]
The cover 50U is adhered to the top surface of the spacer 40U so that the synthetic resin base
material contacts the spacer 40U. Further, the cover 50L is bonded to the lower surface of the
spacer 40L so that a synthetic resin base material is in contact with the spacer 40L. The cover
50U is coated with an adhesive with a width of several mm from the lateral edge and the edge in
the depth direction and is adhered to the spacer 40U, and the cover 50L has the lateral edge and
the edge in the depth direction An adhesive is applied to a width of several mm from the inside to
adhere to the spacer 40L. The cover 50 is in a state where it is not fixed to the spacer 40 inside
the portion to which the adhesive is applied. The thickness of the cover 50 is preferably about 10
μm. With this thickness, even if the cover 50 is disposed, the sound pressure of the sound
generated by the vibrator 10 does not extremely decrease as compared with the case where the
cover 50 is not disposed. In the present embodiment, the cover 50 is bonded to the spacer 40 so
that a film of synthetic resin is in contact with the spacer 40, but the conductive film of the cover
50 is bonded to the spacer 40 so as to be in contact with the spacer 40. It is also good.
[0021]
The protective member 60U is adhered to the top surface of the cover 50U. The protective
member 60L is bonded to the lower surface of the cover 50L. The protective member 60U is
coated with an adhesive with a width of several mm from the edge in the lateral direction and the
edge in the depth direction and is adhered to the cover 50U, and the protective member 60L has
the edge in the lateral direction and the depth direction An adhesive is applied in a width of
several mm from the edge of the cover to be bonded to the cover 50L. The protective member 60
is not fixed to the cover 50 on the inner side of the portion to which the adhesive is applied.
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[0022]
(Electrical Configuration of Electrostatic Loudspeaker 1) Next, the electrical configuration of the
electrostatic loudspeaker 1 will be described. As shown in FIG. 4, the electrostatic speaker 1
includes an amplifier unit 130 to which an acoustic signal representing a sound is input from the
outside, a transformer 110, and a bias power supply 120 for applying a DC bias to the vibrator
10. The drive circuit 100 is connected. The electrode 20U is connected to the terminal T1 on the
secondary side of the transformer 110, and the electrode 20L is connected to the other terminal
T2 on the secondary side of the transformer 110. The vibrator 10 is also connected to the bias
power supply 120 via the resistor R1. Terminal T3 at the midpoint of transformer 110 is
connected to ground GND, which is the reference potential of drive circuit 100, via resistor R2.
An acoustic signal is input to the amplifier unit 130. The amplifier unit 130 amplifies the input
acoustic signal and outputs the amplified acoustic signal. The amplifier unit 130 has terminals
TA1 and TA2 for outputting an acoustic signal, the terminal TA1 is connected to the terminal T4
on the primary side of the transformer 110 via the resistor R3, and the terminal TA2 is a resistor
R4. , And is connected to the other terminal T5 of the primary side of the transformer. The
conductive film of the cover 50U and the conductive film of the cover 50L are electrically
connected, and both are connected to the ground GND of the drive circuit 100.
[0023]
(Operation of Electrostatic Speaker 1) Next, the operation of the electrostatic speaker 1 will be
described. When an AC acoustic signal is input to the amplifier unit 130, the input acoustic signal
is amplified and supplied to the primary side of the transformer 110. Then, when a potential
difference is generated between the electrode 20U and the electrode 20L by the supplied voltage,
the vibrator 10 between the electrode 20U and the electrode 20L is drawn to either side of the
electrode 20U or the electrode 20L. Such electrostatic force works.
[0024]
Specifically, the polarity of the second acoustic signal output from the terminal T2 is opposite to
that of the first acoustic signal output from the terminal T1. When a positive acoustic signal is
output from the terminal T1 and a negative acoustic signal is output from the terminal T2, a
positive voltage is applied to the electrode 20U, and a negative voltage is applied to the electrode
20L. Since a positive voltage is applied to the vibrating body 10 by the bias power supply 120,
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the electrostatic attractive force between the vibrating body 10 and the electrode 20U to which a
positive voltage is applied is weakened while a negative voltage is applied. Since the electrostatic
attractive force between the electrode 20L and the electrode 20L becomes strong, a suction force
works on the electrode 20L side according to the difference of the electrostatic attractive force
applied to the vibrating body 10, and the electrode 20L side (opposite to the Z-axis direction) To
[0025]
In addition, when the first negative acoustic signal is output from the terminal T1 and the second
negative acoustic signal is output from the terminal T2, a negative voltage is applied to the
electrode 20U, and a positive voltage is applied to the electrode 20L. Be done. Since a positive
voltage is applied to the vibrating body 10 by the bias power supply 120, the electrostatic
attractive force between the vibrating body 10 and the electrode 20L to which the positive
voltage is applied is weakened, while a negative voltage is applied. Since the electrostatic
attraction between the electrode 20U and the electrode 20U is strong, the electrode 20U is
displaced toward the electrode 20U (in the Z-axis direction).
[0026]
As described above, the vibrating body 10 is displaced in the positive direction of the Z axis and
the negative direction of the Z axis (deflection) according to the acoustic signal, and the
displacement direction is sequentially changed to become a vibration, and its vibration state
(vibration Sound waves corresponding to the number, the amplitude, the phase) are generated
from the vibrating body 10. The generated sound waves pass through the elastic member 30
having sound permeability, the electrode 20, the spacer 40, the cover 50, and the protective
member 60, and are emitted as sound to the outside of the electrostatic speaker 1.
[0027]
In addition, since the spacer 40, the cover 50, and the protection member 60 exist outside the
electrode 20, a human body does not touch the electrode 20, and an electric shock can be
prevented. Furthermore, since the conductive film of the cover 50U and the conductive film of
the cover 50L are connected to the ground GND of the drive circuit 100 and have the same
potential, it is possible to prevent an electric shock. Further, since the cover 50 is waterproof,
there is less possibility that the liquid reaches the electrode 20 and the vibrating body 10 to
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reduce the insulation.
[0028]
[Modifications] Although the embodiment of the present invention has been described above, the
present invention is not limited to the above-described embodiment, and can be practiced in
various other forms. For example, the above-described embodiment may be modified as follows
to implement the present invention. The above-described embodiment and the following
modifications may be combined with each other.
[0029]
In the embodiment described above, the electrostatic speaker 1 includes the protection member
60, but the electrostatic speaker 1 may not include the protection member 60. In the
embodiment described above, the adhesive is applied to the edge portion of each member and
adhered to the other member, but the portion to which the adhesive is applied is not limited to
the edge portion of the member. For example, an adhesive may be applied to each member in the
form of a grid to adhere to the other members. In addition, the area to which the adhesive is
applied in the form of dots may be adhered to the other members by regularly providing each
member in a matrix or the like. Further, the method of preventing the members from shifting in
the electrostatic speaker 1 is not limited to the method of fixing with an adhesive, and for
example, the members may be made of double-sided tape. In the embodiment described above,
the conductive film is formed on the entire surface of the insulating layer in the cover 50, but the
conductive film may not be formed on the entire surface of the insulating layer. For example, the
conductive film may be formed in a lattice shape on the surface of the insulating layer of the
cover 50. In addition, it is preferable that the size of the mesh of the grid is a size which can not
pass through the finger of a person.
[0030]
In the embodiment described above, the electrode 20 has a configuration in which the
conductive film is formed on the surface of the film, but the configuration of the electrode 20 is
not limited to this configuration. For example, a conductive metal plate may be used as the
electrode 20. Alternatively, a cloth woven with conductive yarn may be formed into a rectangular
shape, and the cloth formed into a rectangular shape may be used as the electrode 20.
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Alternatively, a conductive film may be formed on a substrate on which a material (for example,
glass or phenol resin) having an insulating property is formed in a plate shape, and the electrode
20 may be formed.
[0031]
In the embodiment described above, the shape of the electrode 20 as viewed from the point on
the Z axis is rectangular, but the shape of the electrode 20 is not limited to the rectangular. For
example, it may be another shape such as a circle, an ellipse or a polygon. The shape of the
vibrator 10 as viewed from the point on the Z axis is not limited to a rectangle, and may be
another shape such as a circle, an ellipse, or a polygon. Further, the shape of the electrostatic
speaker 1 as viewed from the point on the Z axis is not limited to a rectangular shape, and may
be another shape such as a circle, an ellipse, or a polygon, for example. .
[0032]
In the embodiment described above, the electrostatic speaker 1 is configured to sandwich the
vibrating body 10 between the electrode 20U and the electrode 20L, but the electrostatic
speaker 1 is disposed on the front (or back) side of the vibrating body 10 It may be a singleended configuration in which only the electrode 20 is disposed.
[0033]
In the embodiment described above, the dimensions in the X-axis direction and the dimensions in
the Y-axis direction of the respective members excluding the vibrating body 10 are the same in
all, but the dimensions may be different for each member.
For example, the dimension in the X-axis direction and the dimension in the Y-axis direction of
the cover 50 may be longer than other members. Further, when the dimension in the X-axis
direction and the dimension in the Y-axis direction of the cover 50 are longer than the other
members in this manner, the edge of the cover 50U and the edge of the cover 50L are adhered to
each other, and between the cover 50U and the cover 50L The vibrator 10, the elastic member
30, and the electrode 20 may be positioned in a sealed space. According to this configuration,
since the space in which the vibrator 10, the elastic member 30, and the electrode 20 are located
is sealed, the liquid is prevented from reaching the portion through which the current flows from
the outside, and the insulating property is prevented. be able to. Further, the length in the X-axis
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direction and the length in the Y-axis direction of the electrode 20 are longer than the length in
the X-axis direction and the length in the Y-axis direction of the vibrating body 10, and the length
in the X-axis direction of the elastic member 30 and the Y-axis direction The configuration may
be shorter than the length of
[0034]
In the embodiment described above, the elastic member 30 is disposed between the electrode 20
and the vibrating body 10 so that the electrode 20 and the vibrating body 10 are not in contact
with each other, but the electrode 20 and the vibrating body 10 are The configuration for
preventing contact is not limited to the configuration of the embodiment described above. For
example, the electrode 20 and the vibrating body 10 may not be in contact with each other by
arranging a spacer formed of an insulator between the electrode 20 and the vibrating body. FIG.
5 is an exploded view of the electrostatic loudspeaker according to the present modification. The
spacers 31U and 31L are formed of a rigid synthetic resin insulator, and the shape thereof is a
rectangular frame as shown in FIG. In the present embodiment, the heights of the spacers 31U
and 31L are the same. In the electrostatic speaker 1, the electrode 20L is fixed to the lower
surface of the spacer 31L, and the electrode 20U is fixed to the upper surface of the spacer 31U.
Then, the vibrating body 10 is fixed to the upper surface of the spacer 31L, and the lower surface
of the spacer 31U is fixed on the vibrating body 10. In this modification, the vibrating body 10 is
fixed between the spacers 31U and 31L in a tensioned state so as not to cause slack. According
to this configuration, the distance between the electrode 20 and the vibrating body 10 is
maintained by the spacers 31U and 31L, and the vibrating body 10 does not contact the
electrode 20 even if it vibrates.
[0035]
In the present invention, the configuration of the drive circuit 100 may be as shown in FIG. In
addition, in FIG. 6, the same code ¦ symbol is attached ¦ subjected about what is the same
structure as embodiment mentioned above, and description is abbreviate ¦ omitted. In FIG. 6, the
transformer 111 is an insulation transformer (insulation transformer), and the primary side and
the secondary side are electrically isolated. An acoustic signal is input to one terminal T41 on the
primary side of the transformer 111. Further, the other terminal T51 on the primary side of the
transformer 111 is grounded to the ground. Further, one terminal T11 on the secondary side of
the transformer 111 is connected to the amplifier unit 130, and the other terminal T21 on the
secondary side of the transformer 111 is connected to the ground GND of the drive circuit 100
and the amplifier unit 130. It is connected.
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[0036]
An AC (Alternating Current) adapter 200 is a switching type AC adapter, and rectifies an AC
voltage obtained from the AC plug 202 to convert it into a DC voltage. The DC voltage obtained
by this rectification becomes the power supply of the amplifier unit 130. The positive side of the
output of the AC adapter 200 is connected to the amplifier unit 130, and the negative side is
connected to the ground GND of the drive circuit 100. Moreover, the conducting wire of the
negative side of the output of the AC adapter 200 and the grounding side of the AC plug 202 is
connected via the capacitor C1. The capacitance of the capacitor C1 is preferably 1000 pF or
less. If the capacitance is equal to or less than this capacitance, even if the human body contacts
the electrode 20, the current flowing to the human body can be suppressed. In the drive circuit
100, the ground GND of the drive circuit 100 may be grounded with high impedance, and may
have the configuration shown in FIG. In FIG. 7, the same components as in FIG. 6 will be assigned
the same reference numerals and descriptions thereof will be omitted. In the configuration shown
in FIG. 7, the acoustic signal is input to the amplifier unit 130 via the resistor R5. The ground of
the amplifier unit 130 is grounded via the resistor R6 and connected to the ground GND via the
resistor R7. According to the configuration shown in FIGS. 6 and 7, even if the cover 50 is broken
and the human body touches the electrode 20, the current flowing to the human body can be
suppressed.
[0037]
DESCRIPTION OF SYMBOLS 1 ... Electrostatic type speaker, 10 ... Vibrator, 20, 20 U, 20 L ...
Electrode, 30, 30 U, 30 L ... Elastic member, 31 U, 31 L ... Spacer, 40, 40 U, 40 L ... Spacer, 50, 50
U, 50 L ... Cover , 60, 60 U, 60 L: protection member, 100: drive circuit, 110: transformer, 111:
transformer, 120: bias power source, 130: amplifier unit, 200: AC adapter, 201: capacitor, 202:
AC plug
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