JPH0622388

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DESCRIPTION JPH0622388
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
acoustic characteristic adjustment apparatus used to support the determination of parameters
such as balance and frequency characteristics of an acoustic reproduction apparatus which is
suitably implemented as a vehicle.
[0002]
2. Description of the Related Art In recent years, the functions and performance of on-vehicle
audio reproduction apparatuses have been remarkably improved, and therefore the user's
demand for sound quality is extremely high. For this reason, it is necessary to finely set
parameters such as the balance and frequency characteristics of the sound reproduction device
mounted on the car in accordance with the type of car and the like.
[0003]
In a typical prior art, a preamplifier or a graphic equalizer for balance and tone control is used in
combination, and the setting values of the preamplifier, the graphic equalizer, etc. are adjusted
based on the measurement result of the reproduced sound and the actual listening result.
Adjustments are made to achieve the desired characteristics.
[0004]
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1
In the above-described prior art, individual adjustment devices are used for each function such as
volume control and frequency control, and therefore, when a plurality of adjustment devices are
connected and used, Since the S / N and distortion of the input / output circuit of each
adjustment device are superimposed, it is impossible to perform adjustment with high accuracy.
In addition, it is necessary to connect and use individual adjustment devices, which requires time
and effort for measurement and is poor in portability.
[0005]
Furthermore, in order to detect whether a sound with a predetermined sound pressure level
necessary for measurement is output from a speaker mounted on the vehicle body, a measuring
device is connected to the output terminal of the amplifier or the input terminal of the speaker. It
is necessary, and measurement work is complicated. Such a problem is remarkable in the case of
an apparatus for performing acoustic reproduction in a cabin which is a very special acoustic
space as compared to homes and small theaters.
[0006]
An object of the present invention is to provide an acoustic characteristic adjustment device
capable of easily determining the parameters of the acoustic reproduction device.
[0007]
SUMMARY OF THE INVENTION The present invention is directed to adjusting the parameters of
an acoustic reproduction device such that it adapts to the desired acoustic characteristics in the
acoustic space in which the acoustic reproduction device is used. An apparatus comprising:
selection means for selecting one of a plurality of acoustic signal sources and outputting an
acoustic signal from the selected acoustic signal source; and volume control for adjusting the
level of the acoustic signal from the selection means Means, frequency control means for
adjusting the frequency characteristics of the sound signal from the volume adjustment means,
and phase control means for adjusting the phase of the sound signal from the frequency control
means and outputting it to the sounding means. Acoustic characteristic adjustment device.
[0008]
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Further, the volume adjustment means, frequency control means and phase control means of the
present invention are provided at least for each of the front left, front right, rear left and rear
right channels, and the sound volume adjustment means includes left and right balance and front
and rear The phase control means adjusts the balance so that the phase of the acoustic signal of
the rear channel corresponds to the phase of the acoustic signal of the front channel
corresponding to the difference in distance from the acoustic means provided for each channel to
the listening position. It is characterized in that it shifts with respect to the phase.
[0009]
Still further, according to the present invention, in relation to the selection means, the first
display is performed when the voltage level of the acoustic signal from the acoustic signal source
is equal to or higher than a predetermined first voltage, and the first indication is higher than the
first voltage. It is characterized in that an input monitoring means for performing a second
display when there are two or more voltages is provided.
[0010]
According to the present invention, in measuring the acoustic characteristics of the acoustic
space in which the acoustic reproduction device is used, for example, the cabin of a car, and
determining the parameters of the acoustic reproduction device in accordance with the acoustic
characteristics. An acoustic characteristic adjustment device integrally configured to be portable
including a selection unit, a volume adjustment unit, a frequency control unit, and a phase
control unit is used.
[0011]
The selection means selects one of the plurality of sound signal sources and outputs the sound
signal from the selected sound signal source to the volume control means of the next stage.
The acoustic signal source may be, for example, a pink noise generation source serving as a
reference signal for performing measurement with a measuring device, a compact disk
reproducing device for performing an auditory examination by actual acoustic listening, a
magnetic tape reproducing device, etc. is there.
[0012]
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The volume adjustment means adjusts the level of the input sound signal, for example, the leftright balance, the front-rear balance, and the like.
The acoustic signal from the volume adjustment means is input to the frequency control means,
and adjustment of the frequency characteristic, such as tone control, boost control or cutting of
high and low frequencies, is performed.
[0013]
The acoustic signal from the frequency control means is input to the phase control means, for
example, corresponding to the difference in distance from the speaker provided for each of the
front left, front right, rear left and rear right channels to the listening position. Phase control
between channels is performed.
That is, for example, the phase of the sound signal of the rear channel is inverted or shifted by an
arbitrary phase amount with respect to the sound signal of the front channel, etc., so that the
phases of the sounds emitted from the speakers and reaching the listening position are aligned.
Adjusted.
The acoustic signal thus adjusted is acousticized by acoustic means such as a speaker.
[0014]
Therefore, the level and frequency characteristics of the acoustic signal can be adjusted with high
accuracy in relation to the desired values, and a configuration for degrading the acoustic signal
such as an input / output circuit between each means in the adjusting device It can be deleted,
which allows easy adjustment of acoustic characteristics with high accuracy.
In addition, by configuring it to be portable as described above, the adjustment can be performed
more easily.
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[0015]
1 is a block diagram showing the electrical configuration of an acoustic characteristic adjusting
apparatus 1 according to an embodiment of the present invention, FIG. 2 is a front view of the
acoustic characteristic adjusting apparatus 1, and FIG. FIG. 4 is a block diagram for explaining
the configuration when the acoustic characteristic adjustment device 1 is incorporated into the
in-vehicle acoustic reproduction device 2 and the parameters of the acoustic reproduction device
2 are determined. In FIG. 1, for simplification of the description, only one of left and right
channels, for example, the left channel is shown, and the remaining right channel is configured in
the same manner as the left channel and has frequency characteristics as described later.
Adjustment and adjustment of phase characteristics etc. are performed in conjunction with the
left and right channels.
[0016]
An acoustic signal from an acoustic signal source such as the compact disc player 3 or the
magnetic tape reproducing device 4 is input to the acoustic characteristic adjustment device 1,
and pink noise is input via the external input terminal 5. Accordingly, on the back plate 19 of the
acoustic characteristic adjustment device 1, the left and right channel input terminals PI1
corresponding to the compact disc player 3, the input terminal PI2 corresponding to the
magnetic tape reproducing device 4, and the external input terminal 5 are supported. An input
terminal PI3 is provided.
[0017]
The operator determines the parameters corresponding to the acoustic characteristics of the
compartment 11 of the car as described later using the pink noise, and the acoustic signals from
the compact disc player 3 and the magnetic tape reproducing device 4 Adjustment is made
according to the actual hearing of the listeners 12a and 13a in the passenger compartment 11.
[0018]
When the in-vehicle acoustic reproduction device 2 is actually used, a so-called pre-amplifier
amplifier or the like is used instead of the acoustic characteristic adjustment device 1.
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Accordingly, the acoustic characteristic adjustment device 1 outputs acoustic signals of five
channels of the front left and right FL, FR and the rear left and right RL, RR and the low band WO
corresponding to this pre-amplifier amplifier. The acoustic signals of the respective channels are
amplified by power amplifiers AFL, AFR; ARL, ARR; AW (hereinafter collectively referred to as a
reference A when collectively referred to), and then corresponding speakers SFL, SFR; SRL, SRR;
SW (Hereafter, it is indicated by the reference symbol S when it is generically referred to.)
[0019]
In the instrument panel 14 disposed in front of the seats 12 and 13 at the listening position in
the passenger compartment 11, speakers SFL in the front left channel are disposed on the left
side of the listening positions 12 and 13 The speaker SFR of the front right channel is arranged
at the center, and the woofer SW for the low band is arranged at the center. A rear left channel
speaker SRL is disposed on the left side facing the seats 12 and 13 on the rear tray 15 disposed
rearward of the passenger compartment 11, and a rear right channel loudspeaker SRR is
disposed on the right side. ing.
[0020]
The compact disc player 3, the magnetic tape reproducing device 4 and the external input
terminal 5 are inputted from the respective input terminals PI1 to PI3 to the individual contacts
of the rotary switch RS1 as selection means, and from the common contact of the rotary switch
RS1. The acoustic signal of is input to the main volume and loudness adjustment unit 21. The
adjustment unit 21 adjusts the level of the input acoustic signal according to the set value of the
variable resistor VR1, and impedance elements Z1 to Z3 having different impedances connected
via the individual contacts of the rotary switch 2. The loudness correction correction amount for
emphasizing at least one of the bass range and the treble range is set according to which is
selected, and after emphasizing the acoustic signal with the set correction amount, It is output to
the balance adjustment unit 22.
[0021]
That is, as shown in FIG. 5, when the voltage level of the input acoustic signal to the main volume
and loudness adjustment unit 21 is 0.5 Vrms and the 0 dB output level is 0.5 V rms at 1 kHz, for
example, the volume value of the main volume Is 40 dB, when the rotary switch RS1 is connected
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to the unconnected contact point of the impedance element, the output acoustic signal has a flat
characteristic at -40 dB as indicated by the reference symbol .alpha.0. On the other hand, when
the impedance element Z1 is selected, both the low range and the high range are emphasized
greatly as indicated by the reference symbol α1, and when the impedance elements Z2 and Z3
are formed, the emphasis amount and the sharpness change. And, as indicated by the reference
characters .alpha.2 and .alpha.3, the characteristics different from the characteristics indicated by
the reference character .alpha.
[0022]
These characteristics are obtained when the volume value of the main volume is -40 dB, and the
characteristics change continuously according to the volume value of the main volume. For
example, when the volume value of the main volume is 0 dB, the frequency characteristic
becomes flat at 0 dB, regardless of which impedance element is selected by the rotary switch
RS1.
[0023]
The balance adjustment unit 22 adjusts the balance between the left and right of the input sound
signal in accordance with the set value of the variable resistor VR2, and outputs the balance to
the tone control unit 23. The tone control unit 23 emphasizes the low range corresponding to the
setting value of the variable resistor VR3, and emphasizes the high range corresponding to the
setting value of the variable resistor VR4, and then the front channel, the rear channel and the
low range Divide into channels and output.
[0024]
Assuming that the input signal level to the tone control unit 23 is 0.1 Vrms, and the output
voltage level at 1 kHz is 0.312 Vrms as 0 dB indicated by reference symbol β0 in FIG. 6, the
variable resistor VR3 is By adjusting, from the flat characteristic of 0 dB indicated by the
reference mark β0, as shown by the reference marks β1a and β1b, emphasizing the low band
side to, for example, +12 dB and attenuating the high band side to -12 dB it can. Similarly, by
adjusting the variable resistor VR4, the low band side is attenuated to -12 dB from the flat
characteristic of 0 dB indicated by the reference mark .beta. As indicated by the reference marks
.beta.2a and .beta.2b. Can be emphasized up to +12 dB. The so-called turnover frequency fT (a
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frequency of ± 3 dB) in the tone control unit 23 is, for example, 300 Hz on the low frequency
side and 2 kHz on the high frequency side.
[0025]
The acoustic signal of the front channel from the tone control unit 23 is input to the attenuator
unit 24F, and the acoustic signal of the rear channel is input to the attenuator unit 24R, and the
acoustic signal of the low band channel is input to the attenuator unit 24W. The variable
resistors VR5, VR6 and VR7 are individually provided in the respective attenuator units 24F, 24R
and 24W, respectively, and the gain can be adjusted in 1 dB steps, for example, by these variable
resistors VR5 to VR7. By performing gain adjustment with these attenuator units 24F, 24R, 24W,
the difference in output sound pressure level due to the difference in aperture diameter of each
speaker SFL, SFR; SRL, SRR; SW, and the difference in impedance are compensated, and desired
left and right Balance and back and forth balance and low range balance can be obtained.
[0026]
The acoustic signal of the front channel from the attenuator unit 24F is input to the low pass cut
filter unit 30F via the equalizer unit 27F. The acoustic signal of the rear channel from the
attenuator unit 24R is input to the low pass cut filter unit 30R via the phase switching unit 26R,
the equalizer unit 27R, and the phase shifter unit 29R. Furthermore, the low-pass channel
acoustic signal from the attenuator unit 24W is input to the low-pass cut filter unit 30W through
the 3D switching unit 25, the phase switching unit 26W, the low pass filter unit 28, and the
phase shifter unit 29W.
[0027]
In the sound signal processing system of the front channel, the equalizer unit 27F is a so-called
CR type equalizer, and includes two rotary switches RS3 and RS4. The rotary switch RS3 has five
contacts. By switching the rotary switch RS3, it is possible to select four resistors of resistance
values R1 to R4 and a through line in which no resistor is interposed. Further, the rotary switch
RS4 is provided with six individual contacts, and any one of the capacitors of the electrostatic
capacitances C1 to C6 can be selected. The frequency characteristics when the capacitance is
switched to C1 to C6 with respect to each of the resistance values R1 to R4 are shown in FIG. In
FIG. 7, the input voltage level is 0.5 Vrms, and the state where the output voltage level is 0.5 V
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rms at 1 kHz is 0 dB. By selecting and combining the resistance values R1 to R4 and the
capacitances C1 to C6 in this way, desired characteristics are selected from the boost curves
shown in FIG. Can be adjusted, ie equalized.
[0028]
Further, in the sound signal processing system of the rear channel, the equalizer unit 27R is
configured in the same manner as the equalizer unit 27F, and by switching the rotary switches
RS5 and RS6, a desired boost curve can be obtained. When the switch SW2 is turned on, the
phase switching unit 26R inverts the phase of the input acoustic signal by 180 ° and outputs
the inverted signal. Further, the phase shifter 29R is provided with a rotary switch RS8. This
rotary switch RS8 is provided with eight individual contacts, and switching these individual
contacts advances the phase of the no signal processing through output and the bass range as
shown in FIG. 8 by the desired angle. A signal processing output can be obtained.
[0029]
That is, FIG. 8 (1) shows the gain characteristic of this phase shifter 29R, and FIG. 8 (2) shows the
phase characteristic. As apparent from FIG. 8 (2), by selecting the rotary switch RS8, the
frequency which can advance the phase by 90 ° is f1 to f7, for example 50, 80, 125, 200, 315,
500 and 700 Hz. Can be set to each frequency of The sound of the front channel and the sound
of the rear channel are added in normal phase at the listening positions of the driver's seat 12
and the passenger's seat 13 in the passenger compartment 11 by the phase shifter 29R and the
phase switching unit 26R. , Can efficiently obtain the bass range.
[0030]
Furthermore, in the low-pass channel acoustic signal processing system, the phase switching unit
26W is configured in the same manner as the phase switching unit 26R, and the phase of the
input acoustic signal is inverted 180 degrees and output by conducting the switch SW3. it can.
The phase shifter unit 29W is configured in the same manner as the phase shifter unit 29R, and
can switch the phase of the bass range by a desired angle by switching the rotary switch RS9.
[0031]
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Further, the 3D switching unit 25 is provided with a switch SW8, and by conducting the switch
SW8, it is used in a so-called 3D system in which both the left and right channels of low-range
sound with low directivity are reproduced by a common speaker. Then, a monaural acoustic
signal obtained by adding the input acoustic signals of the left and right channels is created and
output. When the switch SW8 is turned off, the normal stereo sound signal is output so that the
low-range sound is reproduced by the left and right individual woofers as the middle-high range
sound.
[0032]
Furthermore, the low pass filter unit 28 is provided with a changeover switch SW4 and a rotary
switch RS7. The rotary switch RS7 has six individual contacts, and can select five cutoff
frequencies f11 to f15, for example 80, 90, 100, 120 and 150 Hz, and a through output. Further,
by switching the changeover switch SW4, the attenuation characteristic can be selected to either
-18 dB / oct or -12 dB / oct. Therefore, the frequency characteristic when the attenuation factor
is selected as -12 dB / oct is shown in FIG. In FIG. 9, the input signal level is 0.5 Vrms, and the
output of 0.5 Vrms at 1 kHz is 0 dB. Thus, it is possible to adjust the amount and texture of the
low range in the compartment 11.
[0033]
Low pass cut filter sections 30F, 30R, and 30W are respectively provided at final stages of the
front channel, rear channel, and low band channel signal processing systems configured as
described above. The acoustic signal from the equalizer unit 27F is input to the low pass cut filter
unit 30F. The low band cut filter section 30F is provided with a rotary switch RS10 and a
changeover switch SW5. The rotary switch RS10 has ten individual contacts, and like the rotary
switch RS7 of the low-pass filter unit 28, it is possible to select the through output and the cutoff
frequency of f21 to f29. By switching the changeover switch SW5, the attenuation characteristic
can be switched to -6 dB / oct and -12 dB / oct. Therefore, FIG. 10 shows the frequency
characteristic of the low-pass cut filter section 30F when the attenuation factor is set to -6 dB /
oct. The cutoff frequencies f21 to f29 are 30, 40, 50, 60, 80, 100, 150, 200 and 300 Hz. The
input signal level is 0.5 Vrms, and the output of 0.5 V rms at 1 kHz is 0 dB.
[0034]
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The low-pass cut filter unit 30R is configured in the same manner as the low-pass cut filter unit
30F, and includes a changeover switch SW6 and a rotary switch RS11. Furthermore, the low-pass
cut filter unit 30W has a changeover switch SW7 that switches the attenuation factor to -6 dB /
oct and -12 dB / oct, and a rotary switch RS12 that can select between the through output and
the five cutoff frequencies f31 to f35. Have. The frequency characteristic when the attenuation
factor of this low pass cut filter 30W is set to -12 dB / oct is shown in FIG. The cutoff frequencies
f31 to f35 are respectively 20, 30, 40, 50 and 60 Hz. The input voltage level is 0.5 Vrms, and the
output of 0.5 V rms at 1 kHz is 0 dB. As a result, it is possible to prevent each speaker S from
inputting an acoustic signal in a bass range below the reproduction band, and to suppress the
occurrence of undesired distortion.
[0035]
On the front plate 18 of the acoustic characteristic adjustment device 1, the variable resistors
VR1 to VR7, the rotary switches RS1 to RS12, and the switches SW1 to SW7 as described above
correspond to the front, rear, and low frequency channels, respectively. It is arranged.
[0036]
The acoustic signals from the low-pass cut filter sections 30F, 30R, and 30W are output from the
output terminals PO1, PO2, and PO3 of the left and right channels provided on the back plate 19.
The audio signal of the low band channel from the output terminal PO3 is input to the speaker
SW through the power amplifier AW as described above. Also, the sound signal of the front
channel from the output terminal PO1 is input from the parametric equalizers EQFL and EQFR to
the speakers SFL and SFR via the power amplifiers AFL and AFR for each of the left and right
channels. Furthermore, the sound signal of the rear channel from the output terminal P02 is
input from the parametric equalizers EQRL and EQRR respectively provided for the left and right
channels to the speakers SRL and SRR via the power amplifiers ARL and ARR.
[0037]
Parametric equalizers EQFL, EQFR; EQRL, EQRR (hereinafter collectively referred to as reference
EQ) have, for example, four resonance frequencies that can be arbitrarily set, and resonance
sharpness at the resonance frequencies, ie, Q and boost / dip gain can also be set arbitrarily.
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[0038]
As described above, at a predetermined listening position in the passenger compartment 11, an
acoustic parameter optimum for the listening position is set based on the setting values of the
variable resistors VR1 to VR7, the switching state of the rotary switches RS1 to RS12, etc. Can be
easily obtained.
Therefore, the acoustic parameters of the acoustic reproduction device 2 used in the passenger
compartment 11 can be easily determined.
[0039]
Further, as described above, by integrally forming each of the units 21 to 30, the configuration of
the input / output circuit between the respective units can be omitted, and deterioration of the
acoustic signal can be suppressed and highly accurate adjustment can be performed. .
Furthermore, the above-mentioned acoustic characteristic adjustment device 1 is configured to
be portable, which also allows easy adjustment of frequency characteristics.
[0040]
Power from the commercial frequency power supply 62 via the power supply switch SW1
through the fuse 61 is supplied to each circuit in the acoustic characteristic adjustment device 1
after being rectified and smoothed by the constant voltage circuit 63.
[0041]
On the other hand, the input sound signal selected by the rotary switch RS 1 is also input to the
input level monitor unit 41.
FIG. 12 is an electric circuit diagram of the input level monitor unit 41. As shown in FIG. The
input level monitor unit 41 generally includes a mixing unit 42, a high pass filter unit 43, a DC
conversion unit 44, a window comparator unit 45, and display elements L1 and L2.
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[0042]
From the rotary switch RS1, an acoustic signal of the left channel is input through a line 40L, and
an acoustic signal of the right channel is input through a line 40R. The acoustic signals of both
channels are added by the mixing unit 42 to be a monaural acoustic signal, and then input to the
DC conversion unit 44 through the high pass filter unit 43.
[0043]
The mixing unit 42 includes a buffer 51 implemented by a differential amplifier or the like,
resistors r1 to r3, and a capacitor c1. The high pass filter unit 43 is configured to include a
resistor r4 and a capacitor c2.
[0044]
The DC conversion unit 44 includes an integrated circuit 52 that rectifies an AC signal into a DC
signal, and external capacitors c3 to c5 that smooth the rectified signal. The DC conversion unit
44 converts the effective value of the input AC signal into a DC voltage level and outputs the DC
voltage level to the window comparator unit 45.
[0045]
The window comparator unit 45 includes differential amplifiers 53 and 54, variable resistors vr1
and vr2, and resistors r5 to r8. The output from the DC conversion unit 44 is divided by the
voltage dividing resistors r5 and r6, and then input to the non-inversion input terminal of the
differential amplifier 53 and also input to the inversion input terminal of the differential
amplifier 54. . The high level voltage + B is divided by the resistor r7 and the variable resistor vr1
and input to the inverting input terminal of the differential amplifier 53, and the voltage + B is
input to the non-inverting input terminal of the differential amplifier 54. Is divided and input by
the resistor r8 and the variable resistor vr2. That is, the first reference voltage V1 is outputted
from the movable piece of the variable resistor vr1, and the second reference voltage V2 is
outputted from the movable piece of the variable resistor vr2.
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[0046]
The reference voltages V1 and V2 are determined as follows. When the voltage applied to each
speaker S is V0, the gain of the acoustic characteristic adjustment device 1 and the parametric
equalizer EQ is GV1, and the gain of each power amplifier A is GV2, in order to obtain a desired
sound pressure level, the voltage V1 is
[0047]
It is chosen that V1 = V0 / (GV1 × GV2). The acoustic characteristics of the passenger
compartment 11 are typically measured at an output of 0.5 W from each speaker S. Therefore,
when the impedance of the speaker S is 4Ω, the voltage V0 is 1.41 Vrms. Therefore, when the
gain GV1 is 10 dB and the gain GV2 is 20 dB, V1 = 44.6 mVrms.
[0048]
When the upper limit of the voltage V0 applied to the speaker S is set to a value 0.3 dB higher
than the voltage V0,
[0049]
From the equation 0.3 = 20 log (V2 / V1), V2 = 46.2 mVrms.
[0050]
When the reference voltages V1 and V2 are set as described above, when the output voltage
from the DC conversion unit 44 derived from the connection point 60 of the voltage dividing
resistors R5 and R6 becomes equal to or higher than the voltage V1, the differential amplifier 53
Derives a high level output, and derives a low level output when it is less than V1.
Further, the differential amplifier 54 derives a low level output when the output voltage from the
DC conversion unit 44 is less than the voltage V2, and derives a high level output when the
output voltage is greater than V2.
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[0051]
The output terminal of the differential amplifier 53 is connected to the high level power supply +
B through the pull-up resistor r9, and the cathode of the display element L1 realized by a light
emitting diode or the like from the inverting buffer 55 through the current limiting resistor r10.
Connected to
The anode of the light emitting diode L1 is connected to the power supply + B. Therefore, when
the potential of the connection point 60 becomes equal to or higher than the first reference
voltage V1, the output of the differential amplifier 53 becomes high level and is inverted by the
inversion buffer 55, and a drive current flows to the display element L1 to light the display
element L1 .
[0052]
The output terminal of the differential amplifier 54 is connected to the power supply + B via a
pull-up resistor r11 and to the cathode of the display element L2 via a current limiting resistor
r12. The anode of the display element L2 is connected to the high level power supply + B.
Therefore, when the potential of the connection point 60 becomes equal to or higher than the
second reference voltage V2, the output level of the differential amplifier 54 becomes low level.
A drive current flows through the display element L2, and the display element L2 is lit.
[0053]
The display element L1 is, for example, a green light emitting diode, and the display element L2
is a red light emitting diode. Therefore, by adjusting the voltage level of the acoustic signal input
to the input terminals PI1 to PI3 within the range in which the display element L1 is turned on
and the display element L2 is turned off, each speaker S can receive The sound of the optimal
output sound pressure level required for measurement of acoustic characteristics can be emitted.
As described above, the optimum measurement conditions can be set by a simple operation of
adjusting the input signal levels to the input terminals PI1 to PI3 while confirming the two
display elements L1 and L2. Therefore, adjustment can be performed more simply than the
adjustment method using a voltmeter or the like. In addition, it is not necessary to directly
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measure the input signal level to each speaker S, so that level adjustment can be easily
performed.
[0054]
As described above, according to the present invention, since the selection means, the volume
adjustment means, the frequency control means and the phase control means are integrally
formed, the parameters to be adjusted in each adjustment means are related to each other. Can
be adjusted with high accuracy. Further, input / output circuits between the respective means
can be reduced, whereby deterioration of the acoustic signal can be suppressed and adjustment
can be performed with higher accuracy. Furthermore, the adjustment can be performed more
easily by integrally configuring the respective means so as to be portable.
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