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JPS5461902

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DESCRIPTION JPS5461902
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 apparatus for correcting, in an audio reproduction system, a change in
low range due to a difference in the installation position of a speaker in a listening room. In
general, the speaker frequency transmission frequency characteristics 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 the change
tends to be small in the middle to high range and large in the low range only. Moreover, the
characteristic of the change is that a large peak or dissonage is likely to occur in the 100 to 400
Hz band. As an example, FIG. 1 shows the change of the transmission frequency characteristic
due to the difference in the installation position of the speaker in the 6-mat room room.
According to this, in the case of the installation positions S1 and S3 of the speakers, it can be
seen that a large peak or dissonance occurs in the 100 to 400 Hz band. In such a case, although
the sound is emitted from the speaker at a uniform level, in the listening position a, a noticeable
excess or deficiency of bass occurs. To solve these problems, the following remedies have been
used, but both methods have practical drawbacks. (11 installation of the speaker-the method of
changing the position is the easiest and acoustically theoretical method is also effective.
However, it is difficult to secure the optimum installation position of the speaker in the listening
room of EndPage: 1 in Japan where the room volume is small and there are many cases where
furniture and furniture are provided and doubles as a living room. It is not limited to practicality.
(2) Method of removing harmful reflected sound It is also possible to remove acoustically
harmful reflective surface by absorbing sound to the wall where the reflected sound gives
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harmful level change to the frequency characteristic of the bass region. . However, in general, the
sound absorption method for the low frequency range often can not be used for general homeuse sunning rooms because it requires special acoustic materials and installation methods. (3)
Method of Using Graphic Equalizer A normal graphic equalizer is capable of level adjustment in
every 1 // 3 to 3-member octave band. Therefore, there are various useful applications besides
the correction of the bass level. However, the price is too high compared to audio equipment and
is hardly used in general homes. (4) Method using tone control Generally, the tone control device
built in the audio equipment is, as shown in FIG. 2, a level with a nearly constant slope in the
range below (or above) a certain cutoff frequency So as to regulate the increase or decrease of
Therefore, it is impossible to correct changes in peaks and dips in the 100 to 400 Hz band which
are likely to occur in a general writing room. Therefore, in the present invention, the audio
frequency band is incorporated by taking into account the above problems and inserting it into
an audio device used in general homes or inserting it into an audio reproduction system to
electrically adjust the frequency characteristic. In particular, it is an object of the present
invention to provide an inexpensive and practical transmission frequency characteristic
correction device capable of improving the sound quality in the low frequency range. An
embodiment of the present invention will be described below. FIG. 3 shows an embodiment of the
method of use of the present invention. Reference numeral 1 denotes a recording grader, a tape
recorder, an FM tuner, etc., a sound source device, 2 is a preamplifier including an RIAA% degree
equalizer, 3 is a transmission frequency characteristic correction device according to the present
invention, and 4 is a speaker. The transmission frequency characteristic correction device 3 in
the above configuration operates as a peak dissoge filter in a constant frequency band (for
example, 100 to 4001-1z) of the bass range, and further, the position and level of the peak and
delay center frequency It can be changed. Thus, for example, when the transmission frequency
characteristic of the speaker 5 has a large level peak in the bass region as in the speaker
installation position S1 in FIG. 1, the transmission frequency characteristic correction device 3 is
set to the inverse characteristic of the peak The peak can be eliminated by operating as a dip
filter similar to. Further, in the case where the delay occurs as in the installation position S3 of
the speaker, the transmission frequency characteristic correction device 3 may be used as a peak
filter. Therefore, the transmission frequency characteristic can be corrected without using an
expensive graphic equalizer as in the prior art when using the transmission frequency
characteristic correction device 3 of the present invention. Next, the transmission frequency
characteristic correction device 3 will be specifically described. The peak dissoge filter used in
the present invention has a flat amplitude frequency characteristic and a signal whose phase
monotonously changes from 0 to -2π (radian) together with the frequency boost II (OHz to l-1z),
and there is no phase change. It is constructed based on the principle that delag occurs at the
frequency position where the phase of the former signal is exactly -π when adding with the
signal. FIG. 4 shows a block circuit in the case of configuring the dissoge filter. 11 is an adder, 12
is an all-pass filter circuit that changes the phase of the input signal monotonously to 0 to -2π
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(radian) with increasing frequency, and 14 is an adder. Are connected in this order between the
input terminal IN and the output terminal OUT.
The output of the attenuator 12 is connected to the negative input of the adder 11, and the
output of the adder 11 is connected to the second glass input of the adder 14. The filter circuit
13 is easily configured, for example, by cascading CR bridge circuits 131 and 132 as shown in
FIG. The CR and bridge circuits are positive and negative signals EndPage: No. 2 inserted in series
on the second line 151, 152 of the same resistance R1 + R2 input and output sides of the
capacitor C2 having the same capacitance, C2 The hooks are connected and configured. The
transfer function P (ω) and the amplitude term IP (ω) 1 of this dip filter are respectively shown
by the following equations. IP (ω) 1- (2) where α is the level ratio of the attenuator 12, 0 ≦ α
≦ 1, and T is the time constant of the CR bridge circuit 1311132. According to this, the shape of
the dip obtained by this dip filter is symmetrical on the logarithmic axis, and has a local
minimum value at ω = D. In addition, the level of the minimum value (the depth of 7 'ip)
increases as the level ratio α increases. Therefore, in this dip filter, the position and level of the
dip center frequency can be set arbitrarily by changing the time constant T of the OCR bridge
circuit 131 ° 132 and the level ratio α of the attenuator 12 as components of the filter circuit
13 It can be changed. FIG. 6 shows another block circuit constituting the transmission frequency
characteristic correction device 3. In this case, the adder 11, the Crt grits circuit 13 ++ 132, and
the attenuator -12 ° adder I4 are connected in that order between the input terminal IN and the
output terminal 0 LIT, and the output of the attenuator 12 is the negative input of the adder 11,
CR By connecting the output of the bridge circuit 132 to the second glass input of the adder 14,
it is possible to configure a peak filter which is completely symmetrical with the dissoge filter
and to adjust the position and level of the peak center frequency by the dip. The same is done as
for the filter. FIG. 7 shows still another block circuit constituting the transmission frequency
characteristic correction device 3. In this case, the adder 111, the switch 16+, the attenuator 121,
the adder 11 □, and the CR bridge circuit 13 ++ '132-the adder 141 + 142 are connected in that
order between the input terminal IN and the output terminal OUT. Output of the adder 141
through the second positive input of the adder 141, the output of the attenuator 121 through the
negative input of the adder 111, the output of the adder 14+ through the switch 162 and the
attenuator 122, the negative input of the adder 112, the attenuator By connecting the output of
122 to the plus input of the adder 142, it is possible to configure a switchable peak-dip filter that
can be used.
In this example, the switch 16+ is turned off and the switch 162 is turned on to act as a peak
filter, and the switch 16 + k is turned on and the switch 162 is turned off to act as a size filter. Also, in this example, the level of dip is adjusted by changing the level ratio α of the attenuator12 +, and the level of e is adjusted by changing the level ratio α of the attenuator 122; The
position of the center frequency of is adjusted by the time constant TK of the CR bridge circuit
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131.degree. 132, as in the above-described example. FIG. 8 shows an example of the amplitude
characteristics of the above peak and dissoge filter. FIG. 9 shows the correction result of the
transmission frequency characteristic in the listening room. 1, 4 are characteristics before
correction, 2.5 are characteristics after correction by the transmission frequency characteristic
correction device of the present invention, and 3, 6 are characteristics after correction by
conventional tone control. According to this, when correcting the peak or dip in the low
frequency range, it is certainly effective to use the transmission frequency characteristic
correction device of the present invention. Note that the peak-dip filter configured using the CR
bridge circuit shown in FIG. 5 can be used as a peak dissoge filter for mid-range and high-range
by changing the time constant T of the CR bridge circuit. Is also applicable. Thus, a transmission
frequency characteristic correction device for middle and high tone ranges is also possible. In
addition, the peak dip filter configured by cascade-connecting two CR Brythno circuits adds a
slight improvement to the Tochi or one CR bridge circuit. It is possible to use it as a low cut low
gost filter. Therefore, a transmission frequency characteristic correction device configured by
using such a filter can have the functions of a peak dip filter, a high cut no filter, and a low cut
lobe filter. FIG. 10 shows the improved CI "(Prisono circuit). Insert switches 171 and 172 in
series with resistors R + and R2 on the output side of resistors R and R2 and before the
connection of capacitors CI and C2, respectively. The series circuit of the switch 171 and the
series circuit of the resistor R2 and the switch 172 are respectively connected in parallel. As a
result, the switch 18 ++ 182 is turned on, the switches 17t and 17z are turned off, and R, = 0.
By setting It2 = O, the switch or switch 171 ° 172 + 18t, 182 is turned off to obtain R, == cy, R2oo by changing to the state of R, == cy, R2-oo. It becomes a local quad-strike filter. For example,
by applying the CR 7 ′ ′ lock circuit shown in FIGS. 5 and 10 to CR and bridge circuit
1311132 in the block circuit of the peak / dip filter shown in FIG. 7, respectively, high cut no
Eve-st filter and low-cut low-gust filter can be easily configured. As an example, the transfer
function P (OJ) and its amplitude term IP (ω) 1 when the filter circuit operates as an I-cut filter
are shown by the following equations. Also, in the case of an ibu-st filter, it is indicated by the
reciprocal of each equation. According to this, it is possible to change the slope of the cutoff by
changing the level ratio α of the attenuators 12+ and 122 in FIG. By changing the time constant
T of the CR bridge circuit 13+, 132, it is possible to change the cutoff frequency without
changing the slope of the cutoff of the high cut / high boost filter in FIG. The example of a
change of the inclination of cutoff is shown. As described above in detail, the device of the
present invention is configured to be able to vary the position of the center-to-center
wavenumber of the peak and the deitzo and the value of the extreme value and the minimum
value within a constant frequency band of the same frequency range. It is a thing. Therefore, by
using the above apparatus, it is possible to significantly improve the sound quality of the bass
region by eliminating the peaks and the lags of the bass region which can not be corrected by the
conventional tone control device in the general sunning room. . It can be manufactured at a
significantly lower cost than a sweet, graphic equalizer, and can be built in without increasing the
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cost of the audio equipment itself, which is practical. Also, as a single product, it can be used as a
practical and effective low-pitched sound quality adjustment device. Furthermore, by
independently applying them to both L and R channels, it is easy to make a difference in R
between the two channels in the bass range caused by the difference in the condition of the
reflection surface around both the L and R speakers. Can be corrected. In addition, it can also be
applied to tone control devices for mid-range and high-range by selecting circuit constants
appropriately. Also, by adding switches to the CR circuit, high-cut high-boost filter, low-cut, lowlobe strike It can also be used as a filter and can be applied to multipurpose applications.
4. Brief description of the drawings. FIG. 1 is an illustration of a change in transmission
frequency characteristics according to the installation position of the speaker, FIG. 2 is a block
diagram showing tone lines, FIG. 5 is a block diagram of an OR and a bridge circuit, FIG. Fig. 7
and Fig. 7 are block diagrams showing another embodiment of the device according to the
present invention, Fig. 8 is a peak, amplitude characteristics of the 7 'igg filter, and Fig. 9 is an
illustration of transmission frequency characteristics corrected by the device according to the
present invention. Fig. 10 is a high cut high boost filter. EndPage: C for use in 4 low-cut lobe-st
filters (a block diagram of a bridge circuit, FIG. 11 is a characteristic diagram showing a change
in the slope of cutoff of the high-cut high boost filter. 3 ... Transmission frequency characteristic
correction device, "12, 12+, 122 ... attenuator, 131, 132 ... CR bridge circuit. Patent applicant's
name Fang 1-12 for shooting (Hz) 3rd-EndPage: 5
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