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JPS56122514

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DESCRIPTION JPS56122514
Description 1, title of the invention
Transmission frequency characteristic correction device
3. Detailed Description of the Invention The present invention relates to a transmission frequency
characteristic correction device for correcting, in an audio reproduction system, a change in the
bass range due to a difference in the installation position of a speaker in a training room.
Generally, the transmission frequency characteristics of the speaker in the listening room are
variously changed depending on the volume of the room, the type of the interior material, the
installation position of the speaker, the listening position and the like. The degree of this change
tends to be smaller at EndPage: 1 in the middle to high range and larger at the low range. The
characteristic of this change is that a large peak or dip is likely to occur in the band of about 100
= 400 Hz. -As an example, Fig. 1 shows a change in transmission frequency characteristics due to
the difference in the installation position of the speaker in the 6 tatami room or the swing room.
According to this, it can be seen that different peaks or dips occur depending on the installation
positions 81 to S9 of the speakers. In such a case, although the sound is emitted from the
speaker at a uniform level, an excessive or insufficient feeling of the bass occurs at the listening
position. Although the following improvement measures have been conventionally used for such
a problem, all had the fault on practical use. (1) A method of changing the installation position of
the speaker. It is the easiest and acoustically effective method. However, it is difficult to ensure
the optimum installation position of the speakers in our room, which is small in room volume and
often equipped with furniture and furniture, and it is not always highly practical. (2) How to
remove harmful reflected sound. It is possible to absorb acoustically harmful reflected sound by
applying a sound absorption process to a wall surface where the reflected sound giving a level
change harmful to the frequency characteristic of the low frequency range is generated.
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However, this method can not often be used for general homes. (3) A method using a graphic
equalizer. A conventional graphic equalizer can adjust its level every 1/3 octave to 1/1 octave
band. Therefore, there are various applications other than the correction of the level in the low
range. However, it is more expensive than audio equipment and is hardly used in general homes.
(4) Method using tone control. In general, a tone control device incorporated in an audio device
is designed to adjust the increase and decrease of the level by providing a nearly constant slope
in the range below or above the cutoff frequency as shown in FIG. There is. Therefore, it is
impossible to correct the peaks and dips on the transmission frequency characteristics in the
general writing room.
The present invention is considered as above, operates as a peak and dip filter within a constant
frequency band, and independently has three parameters of peak and dip center frequencies,
level and bandwidth independently in a simple circuit configuration. An object of the present
invention is to provide a variable transmission frequency characteristic correction device.
Hereinafter, the present invention will be described by way of examples. FIG. 3 is a block diagram
of one embodiment of the present invention. In this embodiment, the all-pass type variable phase
shift circuit 1 in which the phase monotonously changes from 0 to −2π radian as the frequency
of the input signal increases and the gradient of the phase change is variable, and the variable
phase shift circuit Variable attenuators 8 and 9 each having the output of 1 as input, a subtractor
10 for subtracting the output signal of variable attenuator 8 from the input signal, and the output
signal of variable attenuator 8 from the output signal of variable attenuator 9 And an adder 11
for adding the output signal of the adder 10 and the output signal of the subtractor 12, the
output signal of the adder 10 is input to the variable phase shift circuit 1, and the adder 11 The
output signal is configured to be taken out from the output terminal OUT. Also, variable phase
shift circuit 1 is connected in cascade to first order phase shift circuits 2 and 3 both having a
transfer function of (1-JωT) / (1 + jωT) and an input signal to variable phase shift circuit 1 A
variable attenuator 4, an output signal of the variable phase shift circuit 1 as an input, and a
variable attenuator 5 operating in conjunction with the variable attenuator 4 and having the
same attenuation ratio, and an input signal to the variable phase shift circuit 1 A subtractor 6
that subtracts the output signal of the variable attenuator 5 and issues an input to the first order
phase shift circuit 2, adds the output signal of the first order phase shift circuit 3 and the output
signal of the variable attenuator 4, and outputs the output signal It comprises an adder 7 as an
output signal of the variable phase shift circuit 1. Here, IN is an input terminal of the
transmission frequency characteristic correction device, and OUT is an output terminal of the
transmission frequency characteristic correction device. Also, ω is the angular frequency of the
input signal of the transmission frequency characteristic correction device, and T is the time
constant of the first-order phase shift circuits 2 and 3. Further, the angular frequency ω of the
input and the signal is the same as the angular frequency of the input signal of the variable phase
shift circuit 10. EndPage: 2 Next, the principle of the present embodiment will be described prior
to the description of the operation of the present embodiment configured as described above.
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Transmission frequency characteristic correction device
FIG. 4 is a block diagram for explaining the present invention in detail, in which the subtractor
12 of the block diagram shown in FIG. 3 and the loop from the variable attenuator 8 to the
subtractor 12 are omitted. The output signal of the variable attenuator 8 is subtracted by the
subtractor 10 from the input signal applied to the input terminal IN, and the output signal of the
subtracter 10 is input to the variable phase shift circuit 1 and the output signal of the variable
phase shift circuit 1 Are input to the variable attenuator 8 and the variable attenuator 9, and a
signal obtained by adding the output signal of the subtracter 10 and the output signal of the
variable attenuator 9 by the adder 11 is taken out from the output terminal OUT. In the circuit
shown in FIG. 4, the input signal applied to the input terminal IN causes phase interference with
the signal passed through the variable phase shift circuit 1, and the level changes in a band
centered on the frequency where the phase changes by -.pi. Highlighted or suppressed to
produce peaks and dips. Therefore, the peak characteristic is shown when the gain of variable
attenuator 8 is gl and the gain gx> gain g2 as in the variable range, and the dip characteristic is
shown when gain gl <gain g2, and the level is the gain difference (g + ˜ It depends on g2). In
addition, when the gradient of the phase change of the variable phase shift circuit 1 changes, the
bandwidths of the peak and dip change as shown in FIG. 5 (b), and the bandwidth of the peak and
dip becomes larger as the gradient of the phase change becomes larger. Becomes narrower. Next,
the operation of the transmission frequency characteristic correction apparatus according to the
embodiment of the present invention shown in FIG. 3 will be described. One embodiment of the
present invention uses the operation principle of the block diagram of FIG. 4 described above.
First, the transfer function R (jω) of the variable phase shift circuit 1 is expressed by the
equation (1) Be Since the numerator and denominator of the R (jω) (1) equation are mutually
dangerous, their amplitude product + naω) 1 is 1. This indicates that the variable phase shift
circuit 1 is an all pass circuit. The phase term ψ (ω) and its derivative dψ / dω are then given
by d = ω (3). Here, go is the gain of the variable attenuators 4 and 5. The following equation (4)
is derived from the equations (2) and (3). Therefore, according to the equation (4), the phase
characteristic of the variable phase shift circuit 1 (1) monotonously decreases to 0 to −2π
radian as the input signal increases. (2) The phase rotates just -π radian when the angular
frequency ω becomes the reciprocal of the time constant T. (3) The slope of the phase change is
determined depending on the gains go of the variable attenuators 4 and 5, and the slope is the
gain g. It becomes steeper as the becomes larger. Therefore, the transfer function S (jω) of the
transmission frequency characteristic correction device of this embodiment shown in FIG. 3 is 8
(jω) = A / B (5) where A = (1 + go) (1 · −gx + gz) It becomes (1- (omega) 2T2) + 2j (omega) T (tgo) (1 + g1-g2) B = (1 + go) (1 + g1) (1- (omega) 2 T2) + 2J (omega) T (1-go) (1-gl).
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Here, the amplitude product 18 (jω) I of the transfer function 8 (jω) is +8 (jω) 1 = hired · (6)
where C = (1 + go) 2 (1-gt + gz) 2 (1-ω2′1 ′ 2) 2 + 4 (1-gO) 2 (1 + gl-g2) 2ω2T2D = (1 + go) 2
(1 + gx) 2 (1-ω2T2) 2 + 4 (1-go) 2 (1-gl) 2ω2T2. EndPage: From the equation (3), the graph of
the amplitude ring lS (jω) 1 shows a peak characteristic or dip characteristic having a maximum
value or a minimum value at ω-1 / T, and this transmission frequency characteristic correction
device is a peak or dip filter It shows that it is. The peak characteristics and the dip
characteristics are respectively symmetrical with each other if the horizontal axis is shown on a
logarithmic scale. That is, the amplitude transmission frequency characteristic of this
embodiment is symmetrical peak or dip characteristic, the angular frequency of the symmetry
axis is given by reciprocal 1 / T of time constant T, and the peak height or dip depth is variable
attenuation If the gain g2 of the unit 9 is fixed, it is determined depending only on the gain g1 of
the variable attenuator 8. The peak characteristic is exhibited when gl> g2 / 2, and the dip
characteristic is exhibited when g1 <g2 / 2. The smaller the gain g1, the deeper the dip, and the
larger the gain g1 within the range of gI <g2, the higher the peak height. The gain g2 of the
variable attenuator 9 defines the upper and lower limits of the peak and dip, and it is usually
convenient to set the value to an appropriate value. Next, the gains go of the variable attenuators
4 and 5 define the bandwidth (or Q) of the peak and dip, and the bandwidth decreases as the
value of the gain go increases in the range of gO <1. From the above description, the features of
the transmission frequency characteristic correction device of this embodiment are as follows. (1)
Amplitude frequency characteristics show symmetrical peak and dip characteristics when the
horizontal axis is indicated on a logarithmic scale, and become maximum or minimum at an
angular frequency where ω = 1 / T. Therefore, the center frequency of peak and dip can be set
by changing the time constant T of the variable phase shift circuit 1. (2) The maximum value of
the peak and the minimum value of the dip can be set independently by fixing the gain g2 of the
variable attenuator 9 and changing the gain gs of the variable attenuator 8. For example, when
the gain g2 is 0.7 and the gain go′′O, changes in peak and dip levels are as shown in FIG. (3)
The bandwidths of the peak characteristic and the dip characteristic can be set independently by
changing only the gain go of the variable attenuators 4 and 5.
An example of the peak characteristics when the bandwidth of the peak characteristics is
changed as the gain g1 = 0.7 is shown in FIG. Next, a specific circuit will be described. FIG. 8 is a
circuit diagram showing an example of a specific circuit configuration of the embodiment of the
present invention shown in FIG. In FIG. 8, OPl, OF2, OPs, OF2, and OPs are buffer amplifiers
consisting of voltage followers, and the operational amplifier OP6, the capacitor C1 and the
variable resistor r3 constitute the first-order phase shift circuit 2, the operational amplifier OP7,
The variable resistor r4 that operates in conjunction with the capacitor C2 and the variable
resistor r3 constitutes a first-order phase shift circuit 3. The resistor r1 and the variable resistor
r2 constitute the variable attenuator 4, and the resistor r5 and the variable resistor r2 operate in
conjunction with the resistor r2 constitute the variable attenuator 5, and OPs represents an
operational amplifier constituting the subtractor 6. And OF2 is an operational amplifier that
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constitutes the adder 7. Further, the resistor r7 and the variable resistor r8 constitute a variable
attenuator 8, and the resistors r9 and rto constitute a variable attenuator 9, in which case the
gain g2 is fixed. Further, 0P10 is an operational amplifier constituting the attenuator 10, 0P11 is
an operational amplifier constituting the adder 11, and 0P12 is an operational amplifier
constituting the subtractor 12. Now, the resistance value between the output terminal of OPs and
the non-inversion input terminal of OF2, the resistance value between the non-inversion input
terminal of OF2 and the ground, the resistance value between the output terminal of OF2 and the
non-inversion input terminal of OF2 , Resistance of the non-inverting input terminal of OF2 to
ground, resistance of the output terminal of OF2 to non-inverting input terminal of OPs, and
resistance of non-inverting input terminal of OPs to ground, R1, i 'T2, P-5, 几 6, R7, and R8, and
the resistances of the resistors r3, r4, r9, and rlo are 1 (3, R4, R9, and atO, respectively, and the
capacitances of the capacitors C1 and C2 are In the case of C11C2, each fixed EndPage: 4
numbers are selected to be as follows. Therefore, the circuit shown in FIG. 8 corresponds to each
block of the block diagram of this embodiment shown in FIG. 3 in a one-to-one manner.
Therefore, its action is exactly the same as described with reference to FIG. The variable resistors
r3 and r4 are variable resistors that set the time constant of the variable phase shift circuit. Next,
a method of using the transmission frequency characteristic correction device of the present
invention will be described. FIG. 9 is a diagram showing an example of this usage method. 13 is a
sound source device such as a record player, tape recorder, 2M tuner, 14 is a preamplifier
including an RIAA characteristic equalizer, 15 is a transmission frequency characteristic
correction device according to the present invention, 16 is a main amplifier, and 17 is a speaker. .
As described above, the transmission frequency characteristic correction device 15 connected
between the preamplifier 14 and the main amplifier 16 operates as a peak or dip filter in a
constant frequency band, for example, 100 to 400 Hz as described above, and also has peak or
dip The center frequency, level and its bandwidth can be set independently. Therefore, for
example, when the transmission frequency characteristic at the time of reproduction of the
speaker 17 has a large level peak in the low frequency band as S1 shown in FIG. 1, the
transmission frequency characteristic correction device 15 is approximated to the inverse
characteristic of the peak. By setting so as to act as a dip filter, the peak can be deleted. Similarly,
when the transmission frequency characteristic dips as shown at 89 in FIG. 1, the dip is
eliminated by setting the transmission frequency characteristic correction device 15 to act as a
peak filter. Can. As described above, according to the present invention, it is possible to operate
as a peak and dip filter within a constant frequency band, and to set three parameters of peak
and dip center frequency, level and bandwidth independently. The circuit configuration for
parentheses is also simple. Therefore, it can be configured at low cost compared to a graphic
equalizer, and can be incorporated in an audio device. Furthermore, by cascading a plurality of
transmission frequency characteristic correction devices according to the present invention, it is
possible to perform fine correction in response to more complex changes in transmission
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frequency characteristics.
4. Brief description of the drawings FIG. 1 is a diagram showing the change in transmission
frequency characteristics due to the difference in the installation position of the speaker. FIG. 2 is
a characteristic diagram of the tone control device. FIG. 3 is a block diagram of an embodiment of
the present invention. FIG. 4 is a block diagram for explaining the principle of one embodiment of
the present invention. FIGS. 5 (a) and 5 (b) are characteristic diagrams for explaining the
operation of the block diagram of FIG. 4; 6 and 7 are diagrams for explaining the operation of
one embodiment of the present invention. FIG. 8 is a specific circuit diagram of an embodiment
of the present invention. FIG. 9 is a block diagram showing a use example of the transmission
frequency characteristic correction device of the present invention. 1 · · Variable phase shift
circuit, 2 and 3 ... 1st order phase shift circuit, 4.5.8 and 9 · Variable attenuator, 6.10 and 12
subtractor, 7 and 11 · · · Adder. Patent Applicant Trio Co., Ltd. EndPage: 5 Fig. 1 □ Good
development comparison (Hz) Fig. 2 Kai Kai (Hz) Fig. 4 □ 1 Violence (b) □ m '! i, cleft EndPage:
6 Fig. 7 (g) Fig. 9 ♂ EndPage: 7
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