JP2014165784

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DESCRIPTION JP2014165784
Abstract: A narrow directivity condenser stereo microphone corresponding to plug-in power is
obtained. SOLUTION: A condenser microphone unit 10 for mids in which a pointing axis is
arranged along a main axis of a microphone body, and for left and right sides arranged
symmetrically with respect to the main axis while the pointing axis is oriented in a direction
orthogonal to the main axis. Condenser microphone units 20 and 30 are connected such that the
output of the mid condenser microphone unit 10 is added to the left and right side condenser
microphone units 20 and 30, and the left and right condenser microphone units 20 and 30 are
connected. Are respectively connected to the connector terminal 21 of the left channel and the
connector terminal 22 of the right channel, and the connector terminal 21 of the left channel and
the connector terminal 22 of the right channel are connected to the condenser microphone unit
10 for mid via the power supply resistors 11 and 12 respectively. Connection It has been.
[Selected figure] Figure 1
コンデンサステレオマイクロホン
[0001]
The present invention relates to a plug-in power-capable condenser stereo microphone.
[0002]
The condenser microphone has a very high output impedance of the microphone capsule, which
is a large body of electroacoustic conversion, and therefore, outputs the impedance by lowering
the impedance by the impedance converter.
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An impedance converter generally comprises a FET, which requires a power supply to operate
the FET.
[0003]
Hereinafter, in the present specification, the term "microphone capsule" refers to an element that
is opposed to each other and mainly includes a diaphragm and a fixed electrode that constitute a
capacitor, and receives electro-acoustic waves and vibrates the diaphragm to perform
electroacoustic conversion. Say Although a microphone capsule may be called a microphone
module, it is called a microphone capsule in this specification. The portion including the
microphone capsule and the impedance converter is referred to as a "condenser microphone
unit" or simply as a "microphone unit". The microphone unit is housed in a microphone case, and
a front mesh, a circuit board, and other members are provided to constitute a microphone.
[0004]
The professional condenser microphone is externally supplied with phantom power via a 3-pin
type XLR connector or the like. Although the original purpose of the phantom power supply is to
supply a polarization voltage to the condenser microphone, the phantom power supply can be
used as an operation power supply of the impedance converter.
[0005]
However, when a condenser microphone is connected to a consumer IC recorder, a video
recorder, etc. (hereinafter referred to as "recording device"), it is not assumed to use a phantom
power supply. Therefore, in recent years, when a microphone plug is connected to a microphone
jack of a consumer recording device, a mechanism is employed in which power is supplied to the
microphone from the power supply provided in the recording device. This mechanism is called
plug-in power.
[0006]
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By the way, there are stereo microphones that are separately recorded in the left channel and the
right channel so that audio with a three-dimensional effect can be recorded and reproduced. As a
stereo microphone, there exists a thing of the structure which accommodated the microphone
capsule of the left channel and the right channel in one housing. Also, in order to obtain a narrow
directional stereo microphone, there is known an MS stereo microphone comprising a mid
capsule whose directivity axis is directed to the main axis direction of the microphone body and a
side capsule whose directivity axis is directed to the direction perpendicular to the main axis. It is
done.
[0007]
The directional characteristics of the side capsule of the conventional MS stereo microphone
were bi-directional. However, bi-directional microphone capsules suffer from high cost.
Therefore, the applicant has previously proposed a stereo narrow directional microphone
provided with a mid capsule and two unidirectional microphone capsules (see Patent Document
1). Two unidirectional microphone capsules are arranged symmetrically about the main axis.
[0008]
According to the invention described in Patent Document 1, although the intended purpose of
realizing a narrow directional stereo microphone can be achieved, so-called plug-in power is not
taken into consideration. That is, as can be understood from the circuit diagram showing the
embodiment of the invention described in Patent Document 1, it is necessary to provide a
terminal VDD dedicated to power supply separately from the left and right signal output
terminals.
[0009]
In the circuit example described in Patent Document 1, for example, it is assumed that the right
output terminal or the left output terminal is connected to the power supply terminal VDD in
order to realize plug-in power. In such a connection, the impedance balance between the right
output terminal and the left output terminal is lost, and the left and right volumes are different,
making it impossible to obtain a stereo output. Further, when both the right output terminal and
the left output terminal are connected to the power supply terminal VDD, the output signals from
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the right output terminal and the left output terminal are the same and become monaural signals.
[0010]
In the circuit example described in Patent Document 1, it is conceivable to connect between the
right output terminal and the power supply terminal VDD, and between the left output terminal
and the power supply terminal VDD by resistors of the same value. In this case, power is supplied
from the recording device to the power supply terminal VDD from the right output terminal and
the left output terminal through the respective resistors, and plug-in power can be realized.
However, the current supplied to the power supply terminal VDD is limited by the abovedescribed resistance, and a sufficient current can not be supplied to an active element such as an
FET constituting the impedance conversion circuit. As a result, there is a drawback that the left
and right output levels become smaller.
[0011]
A zoom microphone that can be used under plug-in power and that can be used as a stereo
microphone has also been proposed (see Patent Document 2). The invention described in Patent
Document 2 includes a center microphone, left and right channel microphones, resistors R1 and
R2 connected in series between the wirings of the left and right channel microphones, and a
changeover switch. The changeover switch switches between a zoom mode in which the center
microphone is connected to the connection point of the resistors R1 and R2, and a stereo mode
in which the connection point of the resistors R1 and R2 is connected to ground and the center
microphone is disabled.
[0012]
The invention described in Patent Document 2 can be used under plug-in power. However, in the
zoom mode, three microphone outputs of the center microphone and the left and right channel
microphones are combined, and it is not possible to output stereo signals separated to the left
and right. In the stereo mode, sound is picked up in the wide-angle range. Thus, the invention
described in Patent Document 2 can not be used as a stereo microphone having narrow
directivity under plug-in power.
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[0013]
JP, 2012-178628, A JP, 2001-28795, A
[0014]
An object of the present invention is to provide a narrow directivity condenser stereo
microphone compatible with plug-in power.
[0015]
The condenser stereo microphone according to the present invention comprises: a condenser
microphone unit having a directional axis arranged along the main axis of the microphone body;
and a directional axis arranged in a direction orthogonal to the main axis and symmetrical about
the main axis. And the left and right side condenser microphone units are connected such that
the output of the mid condenser microphone unit is added to the left side condenser microphone
unit and the right side condenser microphone unit, Capacitor microphone units are respectively
connected to the connector terminals of the left channel and the connector terminals of the right
channel, and the connector terminals of the left channel and the connector terminals of the right
channel are each for the above-mentioned mid via the power supply resistance. The most
important feature that it is connected to a capacitor microphone unit.
[0016]
When the condenser stereo microphone according to the present invention is connected to the
recording device through the connector, power is supplied from the recording device side to the
condenser stereo microphone through the connector terminals of the left and right channels.
The power is supplied to the left and right side condenser microphone units, and is also supplied
from the left and right channel connector terminals to the mid condenser microphone unit
through the power supply resistors.
Thus, a narrow directivity condenser stereo microphone corresponding to plug-in power can be
obtained.
[0017]
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FIG. 1 is a circuit diagram showing a first embodiment of a condenser stereo microphone
according to the present invention.
It is a circuit diagram showing a 2nd example of a condenser stereo microphone concerning the
present invention. It is a graph which shows an example of directivity adjustment by directivity
variable resistance in the said 2nd Example. It is a graph which shows another example of
directivity adjustment by the said directivity variable resistance. It is a graph which shows the
further another example of directivity adjustment by the said directivity variable resistance.
[0018]
Hereinafter, embodiments of a condenser stereo microphone according to the present invention
will be described with reference to the drawings.
[0019]
In FIG. 1, reference numerals 1, 2 and 3 respectively indicate condenser microphone capsules.
Condenser microphone capsules 1, 2 and 3 each have a diaphragm that receives and vibrates a
sound wave, a fixed pole facing the diaphragm with a minute space, and a housing that houses
the diaphragm and the fixed pole. Become. Condenser microphone capsules 1, 2 and 3 have a
known electroacoustic conversion function, and when the diaphragm receives a sound wave and
vibrates, the capacitance between it and the fixed pole changes, converting the sound wave into
an electric signal. Output. The condenser microphone capsule 1 uses, for example, narrow
directivity. The condenser microphone capsules 2 and 3 may be uni-directional capsules.
[0020]
Since the output impedances of the microphone capsules 1, 2, 3 are extremely high, the
impedances are converted by the FETs 5, 6, 7 as impedance converters, respectively, and audio
signals are output. The portion including the microphone capsule 1 and the FET 5 constitutes a
condenser microphone unit 10. The portion including the microphone capsule 2 and the FET 6
constitutes a condenser microphone unit 20. The portion including the microphone capsule 3
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and the FET 7 constitutes a condenser microphone unit 30.
[0021]
The condenser microphone unit 10 is a mid condenser microphone unit, and the directivity axis
is disposed along the main axis of the microphone body, more precisely, with the directivity axis
and the main axis of the microphone body being in alignment. The condenser microphone unit
20 is a condenser microphone unit for the left side, and the condenser microphone unit 30 is a
condenser microphone unit for the right side. The left and right side condenser microphone units
20 and 30 are arranged symmetrically with the directional axes oriented in the direction
orthogonal to the main axis and sandwiching the main axis.
[0022]
The diaphragm and the fixed pole of the microphone capsule 1 are the output end of the
microphone capsule 1, while the fixed pole, for example, the fixed pole is connected to the gate of
the FET 5, and the diaphragm which is the other output end of the microphone capsule 1 is
grounded It is connected. The drain of the FET 5 is connected to the connector terminal 21 of the
left channel through the power supply resistor 11 and to the connector terminal 22 of the right
channel through the power supply resistor 12. The source of the FET 5 is connected to the
ground via a source resistor 51 and to the output end of the microphone capsule 2, 3 via a
capacitor 52. The microphone capsules 2 and 3 also have the diaphragms and fixed poles of the
microphone capsules 2 and 3 as output ends, and one of the output ends of the microphone
capsules 2 and 3, for example, the diaphragm and the source of the FET 5 are connected . This
connection relationship is a connection relationship in which the output of the condenser
microphone unit 10 for the mid is added to the condenser microphone unit 20 for the left side
and the condenser microphone unit 30 for the right side. The value of the power supply resistor
11 and the value of the power supply resistor 12 are equal.
[0023]
The output end of the microphone capsule 2, for example, the fixed pole is connected to the gate
of the FET 6, and the output end of the microphone capsule 3, for example, the fixed pole is
connected to the gate of the FET 7. The drain of the FET 6 is connected to the connector terminal
21 of the left channel, and the drain of the FET 7 is connected to the connector terminal 22 of
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the right channel. The sources of FETs 6 and 7 are connected to ground. A ground terminal 23 is
connected to the ground.
[0024]
The connector terminal 21 of the left channel, the connector terminal 22 of the right channel,
and the ground terminal 23 constitute, for example, a three-pole connector called a stereo mini
plug. When the three-pole connector is connected to a connector of a recording device such as an
IC recorder or a video recorder, audio signals of left and right channels are input from the
connector terminals 21 and 22 to the recording device. The ground on the recording device side
and the ground terminal 23 on the microphone side are connected.
[0025]
Further, the power supply of the recording device is connected to the connector terminal on the
recording device side corresponding to the connector terminals 21 and 22. Therefore, the power
supply of the recording device is supplied to the drain of the FET 6 through the connector
terminal 21 and to the drain of the FET 7 through the connector terminal 22. Further, the power
supply of the recording device is supplied to the drain of the FET 5 through the connector
terminal 21 and the power supply resistor 11, and to the drain of the FET 5 through the
connector terminal 22 and the power supply resistor 12.
[0026]
The condenser microphone unit 10 for the middle, the condenser microphone units 20 and 30
for the left and right sides, and the associated resistors and capacitors are incorporated in a
microphone case to constitute a condenser stereo microphone. The connector terminals 21, 22,
23 may be fixedly provided in the microphone case, or may be provided at the tip of a cable
pulled out from the microphone case.
[0027]
When the microphone-side connector is connected to the recording device, the power of the
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recording device is supplied to the drains of the FETs 6 and 7 through the connector terminals
21 and 22 as described above, and the FETs 6 and 7 perform the desired impedance conversion
operation. The power applied to the connector terminals 21 and 22 is supplied to the drain of the
FET 5 from the connection position of the power supply resistors 11 and 12 through the power
supply resistor 11 and the power supply resistor 12, respectively, and the FET 5 performs the
intended impedance conversion operation. .
[0028]
The source side of the FET 5 corresponding to the mid condenser microphone capsule 1
constitutes an additional system to the left and right condenser microphone units 20 and 30 for
the output signal of the mid condenser microphone unit 10. By appropriately setting the values
of the power supply resistors 11 and 12, the power supply system to the drain of the FET 5 can
be realized by the left and right side condenser microphone units 20 of the output signal of the
microphone unit 10 on the source side of the FET 5. It is separated from the signal addition
system to 30. Therefore, the influence of the power supply system to the drain of the FET 5 on
the signals of the left and right channels is minor, and the separation of the signals of the left and
right channels has no problem in practice.
[0029]
The operation of the above embodiment will be described. From the microphone unit 10, the
output signal of the microphone capsule 1 is impedance converted by the FET 5 and output. This
output signal is input to the gate of the FET 6 through the capacitor 52 and the microphone
capsule 2. The output signal of the microphone unit 10 is also input to the gate of the FET 7
through the capacitor 52 and the microphone capsule 3. The FETs 6 and 7 are source grounded
circuits. The FET 6 impedance-converts the sum of the output signal of the microphone unit 10
and the output signal of the microphone capsule 2, and outputs the result to the connector
terminal 21. The FET 7 impedance-converts the sum of the output signal of the microphone unit
10 and the output signal of the microphone capsule 3, and outputs the result to the connector
terminal 22.
[0030]
The microphone capsule 1 is narrow directivity with its pointing axis along the main axis of the
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microphone, and the microphone capsule 2 is unidirectional with its direction 90 degrees to the
left with respect to the main axis direction. The signal output to the connector terminal 21, that
is, the output signal of the FET 6 is a narrow directivity signal inclined to the left as in the left
channel output of the conventional MS stereo narrow directional microphone. The signal output
to the connector terminal 22, that is, the output signal of the FET 7 becomes a narrow directivity
signal inclined to the right, similarly to the right channel output of the conventional MS stereo
narrow directional microphone. Thus, narrow directional stereo signals are output from the
connector terminals 21 and 22.
[0031]
Next, the phases of the signals output from the microphone units 10, 20, and 30 will be
described. The output signal of the microphone capsule 1 for the mid phase is positive. Since the
FET 5 outputs a signal from the source side, the output signal of the FET 5 is in positive phase.
The microphone capsules 2 and 3 for the side are disposed at positions sufficiently close to the
microphone capsule 1, and the output thereof can be regarded as positive phase. Therefore, the
input of the FET 6, that is, the output of the FET 5 and the output of the microphone capsule 2
are added together in the positive phase.
[0032]
Since the FET 6 has a source grounded and a drain output, its output signal is inverted, and the
reverse phase is output to the connector terminal 21. The signal output from the drain of the FET
5 to the connector terminal 21 through the power supply resistor 11 is in reverse phase. Thus, at
the connector terminal 21, the output signal of the FET 6 and the output signal of the FET 5
appear in opposite phase, and are added together. Similarly, the output signal of the FET 7 and
the output signal of the FET 5 appearing at the connector terminal 22 are both in reverse phase,
and the output signals of the FET 7 and the FET 5 become signals summed together.
[0033]
Thus, according to the embodiment shown in FIG. 1, there is an advantage that high output levels
can be secured without cancellation due to the phase difference between the output signals of
the condenser microphone unit for mid 10 and the condenser microphone units 20 and 30 for
side. .
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[0034]
As described above, in the embodiment shown in FIG. 1, the MS type capacitor stereo
microphone is configured by including the mid condenser microphone unit 10 and the left and
right side condenser microphone units 20 and 30.
In addition, a narrow directivity condenser stereo microphone can be obtained by configuring the
MS condenser stereo microphone. According to this embodiment, by connecting to the recording
device through the connector, it is possible to receive the operation power supply from the
recording device side, and so-called plug-in power can be realized.
[0035]
Next, a second embodiment of a condenser stereo microphone according to the present invention
will be described with reference to FIG. The second embodiment differs from the first
embodiment in having a directional variable resistor 14. The directivity variable resistor 14 is
connected between the position where the output of the mid condenser microphone unit 10 is
added to the left and right side condenser microphone units 20 and 30 and the ground. More
specifically, the directivity variable resistance 14 is connected between the connection point of
the diaphragms of the microphone capsules 2 and 3 and the capacitor 52, and the ground.
[0036]
By changing the value of the directivity variable resistor 14, the output level of the mid
condenser microphone unit 10 added to the left and right side condenser microphone units 20
and 30 is adjusted. Therefore, the degree of influence of the condenser microphone unit 10 on
the left and right side condenser microphone units 20 and 30 changes, and the directivity of the
signal appearing on the connector terminals 22 and 23 of the left and right channels changes.
[0037]
FIGS. 3 to 5 sequentially show changes in the directivity of the signal appearing at the connector
terminal of the left or right channel by varying the value of the directional variable resistor 14.
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However, the directivity of only one of the left and right channels is shown, while the directivity
of the channel appears symmetrically with respect to a line connecting 0 degrees and 180
degrees.
[0038]
FIG. 3 shows a case where the value of the directivity variable resistance 14 is set to an
appropriate value to increase the degree of influence of the mid condenser microphone unit 10
on the left and right side condenser microphone units 20 and 30. As shown in FIG. 3, it becomes
a cardioid-shaped directivity characteristic in which the directivity axis is inclined by about 30
degrees. Also, the directivity angle is a narrow angle.
[0039]
FIG. 4 shows the case where the value of the directional variable resistor 14 is adjusted to reduce
the output level of the condenser microphone unit 10 for the mid. The output of the mid
condenser microphone unit 10 is shunted to the ground, and the degree of influence of the mid
condenser microphone unit 10 on the left and right side condenser microphone units 20 and 30
is reduced. As shown in FIG. 4, the pointing axis is inclined by about 60 degrees, and the cardioid
shape collapses to provide a pointing characteristic in the form of broadening the pointing range.
[0040]
FIG. 5 shows the case where the value of the directional variable resistor 14 is made zero and the
output level of the mid condenser microphone unit 10 is made zero. Since the influence of the
condenser microphone unit 10 for the middle is eliminated, the left and right condenser
microphone units 20 and 30 output audio signals with directivity characteristics unique to the
respective units. As shown in FIG. 5, the pointing axis is inclined by about 90 degrees, and the
cardioid shape is further broken and the pointing angle becomes wide.
[0041]
According to the condenser stereo microphone of the second embodiment, the directivity of the
output signals of the left and right channels can be easily changed only by adjusting the value of
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the directivity variable resistor 14.
[0042]
According to the condenser stereo microphone according to the present invention, so-called plugin power can be realized in the stereo microphone provided with the condenser microphone unit
for the middle and the condenser microphone unit for the side.
Therefore, for example, the power supply of the recording device can be used as the power
supply of the microphone only by being attached to various recording devices for consumer use,
and the usability of the condenser stereo microphone is improved.
[0043]
1 microphone capsule (for mid) 2 microphone capsule (for left side) 3 microphone capsule (for
right side) 5 FET (for mid) 6 FET (for left side) 7 FET (for right side) 10 microphone unit (for mid)
11 Power supply resistance 12 Power supply resistance 14 Directional variable resistance 20
Microphone unit (for left side) 21 Connector terminal for left channel 22 Connector terminal for
right channel 23 Ground terminal 30 Microphone unit (for right side)
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