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DESCRIPTION JP2006157829

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DESCRIPTION JP2006157829
PROBLEM TO BE SOLVED: To improve reproduction characteristics of a small volume signal from
a speaker. SOLUTION: In the case of performing correction processing for outputting an input
audio signal from a speaker device having a predetermined input / output characteristic, an
output for an input signal at a predetermined level or more as a predetermined input / output
characteristic of the speaker device When the linearity of the level is substantially ensured and
the output level with respect to the input signal falls below a predetermined level, the decrease in
the output level with respect to the signal component below the predetermined level of the input
audio signal is Perform compensation processing to compensate. [Selected figure] Figure 2
Audio signal processing method and apparatus
[0001]
The present invention relates to an audio signal processing method and apparatus for performing
characteristic correction in the case of reproducing an audio signal from a speaker apparatus,
and is particularly suitable for use in a speaker apparatus for high fidelity reproduction capable
of reproducing high sound quality. It relates to technology.
[0002]
Conventionally, various configurations have been put to practical use as speaker devices for high
fidelity reproduction capable of high-quality sound reproduction.
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For example, there is a three-way speaker device in which a reproduction band of an audio signal
is divided into three bands of low, middle, and high bands, and separate speaker units are
prepared for each band. This 3-way speaker device can reproduce the input audio signal
faithfully from the low band to the high band by using a speaker unit for each band that has
good reproduction characteristics in each band. Generally, the reproduction characteristic is
better than that of a so-called full range type speaker unit in which audio of all bands is output
by one speaker unit.
[0003]
Further, in addition to the configuration for enhancing the reproduced sound of the speaker
device such as the 3-way configuration and the 2-way configuration as described above, the
characteristic of the audio signal itself supplied to the speaker device is It is also performed to
correct on the device side to improve the characteristics of the audio output from the speaker
device as a result. For example, an audio amplifier device that performs processing such as
amplification of an audio signal that drives a speaker device may perform correction called
loudness control. This loudness control performs correction processing that enhances the output
level compared to the midrange part with the bass part and the trebleband part, and corrects that
the low band and the high band are heard mainly when the volume is small. It is a thing.
[0004]
Patent Document 1 describes an example of a reproduction configuration when loudness
correction is performed. JP 2002-171589 A
[0005]
However, since the loudness-controlled playback sound simply boosts the signal of a specific
frequency band almost uniformly regardless of the level, it is not strictly a reproduction that is
faithful to the input audio signal, but rather the input audio. It has been desired to develop a
speaker device capable of faithful reproduction to a signal. That is, since the conventional
loudness-controlled reproduction sound is reproduced by enhancing the sound which is hard to
hear when the volume is small, the bass and treble parts become easier to hear compared to the
reproduction sound without the loudness control, and the sound quality to some extent Although
it is effective to improve the signal of a specific frequency band even if it is a small level or a
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2
large level, it is possible to enhance also the signal component which does not need to be
enhanced. In some cases, the result may be an unnatural reproduced sound.
[0006]
Here, to explain the problem of the reproduced sound in the conventional speaker device, there
is a problem of a small amplitude signal as an example in the case where the reproduced sound
does not faithfully reproduce the input audio signal. That is, for example, as shown in FIG. 9A, it
is assumed that an input audio signal S1 having a waveform in which a waveform having a
relatively large amplitude and a waveform having a relatively small amplitude are continuous is
input to the speaker. At this time, the waveform of the output audio signal S2 from the speaker is
substantially the same as that of the input signal S1 for the waveform of relatively large
amplitude, but the amplitude of the waveform of relatively small amplitude is higher than that of
the input signal S1. It tends to be smaller. This is because a speaker unit having a general
diaphragm capable of outputting a relatively loud sound has poor reproduction characteristics of
a small volume signal with a small amplitude, and the linearity of the input / output
characteristics of the small volume signal ( Linearity) is not ensured.
[0007]
Similarly, for example, as shown in FIG. 9 (b), the input audio signal S3 of a waveform of
relatively large amplitude and the input audio signal S4 of a waveform of relatively small
amplitude overlap in time, so that they are inherently The audio signal S5 obtained by combining
the two signals S3 and S4 is output, but the output audio signal S6 having a waveform whose
level is lower than the waveform of the combined signal S5 is output from the speaker. For
example, when the sounds of various instruments are simultaneously reproduced as the audio to
be reproduced from the speaker, such as symphony, such an output state may occur.
[0008]
Further, for example, as shown in FIG. 9C, when there is an impulse signal in which the amplitude
of the signal of a specific single frequency gradually decreases as the input audio signal S7, the
waveform of the output audio signal S8 from the speaker Also, as the level decreases, the
followability deteriorates.
[0009]
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In any of the examples shown in FIG. 9, the output level of the small volume signal having a small
amplitude becomes smaller than the input signal level as the output from the speaker, and the
linearity of the small signal is not maintained.
When frequency analysis is performed on the state shown in FIG. 9, for example, the state shown
in FIG. The example of FIG. 10 is an example in which the sensitivities of the fundamental wave
f1 and the harmonics f2 and f3 that are harmonics of the fundamental wave are analyzed. The
fundamental wave f1 with a high level is output as it is, but the harmonics f2 and f3 whose levels
are smaller than the fundamental wave have output sensitivities shown by a solid line that is
lower than the original level shown by a broken line. ing.
[0010]
FIG. 11 is a diagram showing output characteristics from low to high frequencies at multiple
levels of signal levels, and FIG. 11 (a) is an ideal characteristic, and FIG. 11 (b) is an actual
speaker output It is the figure which showed the characteristic. As shown in FIG. 11A, in an ideal
state, it is assumed that the four levels L1, L2, L3, and L4 have flat characteristics from low to
high frequencies at substantially equal intervals. At this time, as the actual output characteristics
of the speaker shown in FIG. 11B, output characteristics substantially equivalent to the ideal
characteristics can be secured for the levels L1, L2, and L3 having high output levels, but the
lowest level The characteristic of L4 is a level which is lowered in any frequency band by the
sensitivity α from the originally necessary level.
[0011]
It is an input / output characteristic diagram of FIG. 12 that such a decrease in sensitivity is
viewed as a characteristic of a specific frequency. As shown in FIG. 12, the characteristic x of the
broken line in which the output level increases linearly with the increase of the input signal level
to the speaker has to be originally required, but in fact it is a certain level or more In this case,
the level changes almost linearly, but below a specific level, the movement of the diaphragm with
respect to the input is bad, and the output sensitivity to the input has a characteristic y of a curve
that is very bad.
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[0012]
Specifically, for example, assuming that the maximum level of listening by a general speaker is
70 to 100 SPL (sound pressure level), a signal which is -30 dB to -60 dB lower than the
maximum level is correct for the maximum level- It means that the volume lowered by 30 dB to 60 dB is not output (not proportional). Assuming that the volume of the output of the amplifier
device is reduced by 50 SPL from 100 SPL, the volume at around 50 SPL should normally be
obtained, but actually, for example, only an output of 40 SPL that is 10 SPL lower than that is
obtained It will not be possible. That is, it means that linearity can not be accurately obtained,
and it has been found by analysis of the present inventor that it is one of the major causes for not
obtaining satisfactory sound quality.
[0013]
Note that the characteristics described so far are the characteristics in the case where the
diaphragm is a relatively large speaker unit capable of relatively large volume output, but
conversely, for example, as in the case of a speaker unit for headphones, small volume In the case
of a small and lightweight speaker unit manufactured for the output of the above, the linearity of
the input and output can be kept relatively good at the time of small volume and the linearity of
the input and output characteristics at the time of large volume can not be maintained. There is
also a configuration.
[0014]
The present invention has been made in view of the foregoing, and it is an object of the present
invention to improve the reproduction characteristics of a small volume signal from a speaker.
[0015]
The present invention is a case where correction processing for outputting an input audio signal
from a speaker device having a predetermined input / output characteristic, and an output for an
input signal at a predetermined level or more as a predetermined input / output characteristic of
the speaker device When the linearity of the level is substantially ensured and the output level
with respect to the input signal falls below a predetermined level, the decrease in the output level
with respect to the signal component below the predetermined level of the input audio signal is
The correction processing is to be performed.
[0016]
By doing this, as the audio signal output from the speaker device, an input / output characteristic
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corrected according to the characteristic of the speaker device becomes an almost linear audio
signal, and in particular, a comparison in which the output level is originally insufficient A low
level signal will be output well at the original level.
[0017]
According to the present invention, as an audio signal output from a speaker device, an input /
output characteristic corrected in accordance with the characteristics of the speaker device
becomes an almost linear audio signal, and in particular, the output level is relatively insufficient.
The level signal is output well at the original level, and the reproduction sound quality can be
dramatically improved.
[0018]
In this case, as the correction processing is performed so that the correction processing to
compensate for the decrease in the output level is performed substantially uniformly in almost all
frequency bands output by the speaker device, the reproduction characteristics can be improved
in all frequency bands. It is possible to reproduce with high fidelity to the input audio signal,
which is completely different from the conventional enhancement of only a specific band such as
loudness control.
[0019]
Also, by performing correction processing using a filter, it is possible to configure a relatively
simple circuit using the filter.
[0020]
Further, by performing the correction process using the transformer, it is possible to perform
correction using the characteristics of the transformer.
[0021]
Further, by correcting the input audio signal by digital operation processing, it becomes possible
to easily set any correction characteristic by digital operation.
[0022]
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
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1 to 4.
FIG. 1 is a diagram showing an example of a system configuration according to the present
embodiment.
The present embodiment is a speaker device connected to an audio reproduction system, and
FIG. 1 is a diagram showing an example of the entire system configuration.
In this example, the audio signal source 10 is connected to the amplifier device 20, and the audio
signal source 10 reproduces an audio signal recorded (stored) in a medium such as a CD (disc) or
memory, and reproduces the audio signal. The audio signal to be output is supplied to the
amplifier device 20, and the amplifier device 20 performs processing to convert the audio signal
into an audio signal for driving the speaker device.
[0023]
In the case of this example, the audio signal output from the audio signal source 10 is a signal of
two channels of an audio signal for the left channel and an audio signal for the right channel.
The left channel audio signal output from the amplifier device 20 is supplied to the left channel
speaker device 30L for output, and the right channel audio signal is supplied to the right channel
speaker device 30R for output.
[0024]
The left-channel speaker device 30L and the right-channel speaker device 30R basically have the
same configuration (however, the outer shape may be slightly different, for example, they may be
laterally symmetrical).
In the following description, the left and right channel speaker devices 30L and 30R may be
referred to as the speaker devices 30 attached with the same symbols except for L and R when
the channels are not distinguished.
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[0025]
The configuration of each of the speaker devices 30L and 30R will be described. Each of the
speaker devices 30L and 30R includes one speaker unit 31 (FIG. 2) as a speaker unit as sound
output means for outputting audio.
Each of the speaker units 31 is a so-called full-franking type speaker unit having a characteristic
that is substantially flat in the audible band as a characteristic seen from the output frequency
band and that is outputted from low to high frequencies There is a relatively large diaphragm
and a relatively large speaker unit capable of outputting a high volume signal.
As for the speaker unit 31, since the diaphragm is relatively large, the linearity (linearity) of the
input / output characteristics of large signals above a predetermined level is substantially
maintained, and the linearity of the input / output characteristics is not secured below the
predetermined level. The output signal level is inferior to the input signal level.
That is, the speaker unit having the characteristic y described with reference to FIG. 12 in the
background art section is used.
A speaker unit having such characteristics is general as a speaker.
[0026]
In the present embodiment, in the audio reproduction system to which the speaker device 30
using the speaker unit 31 having such characteristics is connected, the characteristic correction
of the signal is performed on the side of the amplifier device 20 that processes the audio signal
supplied to the speaker device 30. It is intended to
[0027]
FIG. 2 is a diagram showing a configuration for characteristic correction in the amplifier device
20 of the present example, and shows a connection configuration up to the speaker unit 31
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constituting the speaker device 30. As shown in FIG.
As shown in FIG. 2, the audio signal obtained at the audio signal input terminal 21 of the
amplifier device is supplied via the buffer amplifier 22 to the primary side of the transformer 23
prepared as the characteristic correction means. Then, the signal obtained on the secondary side
of the transformer 23 is supplied to the amplifier 24 to be amplified for driving the speaker, and
the amplified audio signal is supplied to the speaker unit 31 in the speaker device 30 to be an
audio signal. Output (sounds out). In the amplifier 24, for example, the amplification factor is
variably set in accordance with the adjustment state of a volume (not shown) for volume
adjustment. Alternatively, the volume adjustment may be performed using amplification means
other than the amplifier 24.
[0028]
FIG. 3 is a diagram showing an example of the characteristic corrected by the transformer 23. In
FIG. 3, a characteristic a indicated by a broken line is a characteristic in which the linearity is
linearly proportional to the increase and decrease of the input level and the increase and
decrease of the output level, and is shown for reference. Characteristic b shown by a solid line is
a characteristic corrected by the transformer 23 of this example.
[0029]
As indicated by the characteristic b, when the signal is transmitted from the primary side to the
secondary side, the increase and decrease of the input level and the increase and decrease of the
output level are linear when the signal is transmitted from the primary side to the secondary
side. In the range below a predetermined level, the lower the output level with respect to the
input level, the higher the increase rate compared to the characteristic a. It is made to become
the characteristic shown by the curve which has not taken the linearity which becomes high.
[0030]
Here, with regard to the level position at which the curve and the straight line of the
characteristic b of the transformer 23 change, a range of levels at which the linearity of the input
/ output characteristic is substantially maintained as the characteristic of the connected speaker
unit 31; The linearity of the input / output characteristics is made to substantially coincide with
the level of the change point (that is, the above-described predetermined level) with the range of
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9
the level where the linearity is not secured.
Specifically, when the peak level of the audio signal is 0 dB, for example, when the range in
which the linearity of the input / output characteristics of the speaker unit 31 is secured is from
0 dB to -25 dB, -25 dB is set to a predetermined level Then, the signal characteristic is not
changed in the range of 0 dB to -25 dB, and the curve of the characteristic b is set at -25 dB or
less. Further, the characteristics for determining the shape of the curve of the characteristic b of
the transformer 23 are also set to characteristics obtained by inverting the input and output of
the input / output characteristics of the speaker unit as shown in FIG. The setting of such
characteristics is set by, for example, the shape, material, and the like of the transformer 23.
[0031]
Note that the characteristic b shown in FIG. 3 shows the characteristic at a specific frequency, but
in the case of this example, substantially the same characteristics are obtained in all audible
bands that can be reproduced by the speaker unit 31. It is made to have it.
[0032]
FIG. 4 is a diagram showing a state in which an audio signal is output from the speaker device 30
by the correction by the transformer 23 having such characteristics as an output characteristic
from low to high in multiple signal levels. is there.
FIG. 4A is a diagram showing an output characteristic (i.e., an uncorrected output characteristic)
possessed by the speaker device 30 of this embodiment. FIG. 4 (a) is the same as the speaker
characteristic shown in FIG. 11 (b) as the background art. That is, as shown in FIG. 4A, for the
levels L1, L2 and L3 having high output levels, an output characteristic substantially equivalent
to the ideal characteristic can be secured, but for the output characteristic at the lowest level L4,
The level is lowered in any frequency band by the sensitivity α from the originally necessary
level.
[0033]
Here, as correction of the characteristic b shown in FIG. 3 is performed in all the frequency bands
by correction in the amplifier device 20, the output characteristics of the signal input to the
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10
amplifier device 20 are as shown in FIG. As shown in the figure, for the levels L1, L2 and L3
where the output level is high, there is no change with the input level, but for the output
characteristics of the lowest level L4, it rises from the original level by the sensitivity β and in
any frequency band It has become a level. Here, the increased sensitivity β is set to a level that
substantially compensates for the sensitivity α that decreases in the speaker device 30.
[0034]
With such characteristics, the audio signal processed by the amplifier device 20 is output from
the speaker device 30. As a characteristic of the audio output from the speaker device 30, as
shown in FIG. 4C. The four levels L1, L2, L3 and L4 have flat characteristics from low frequency
to high frequency at almost equal intervals, and all frequencies of input and output are almost
equal to the ideal characteristics shown in FIG. It becomes a good characteristic that matches
regardless of the level in the band.
[0035]
Therefore, according to the audio reproduction system of this embodiment, the audio signal
reproduced from the audio signal source 10 can be output from the speaker device 30 with high
sound quality.
Such reproduction characteristics faithfully reproduce the input audio signal, which is completely
different from the processing of enhancing the signal of a specific frequency band regardless of
the level, such as the conventionally known loudness control. It is a characteristic.
[0036]
Note that the reproduction system of this embodiment is applicable to various audio
reproduction systems, and in the example shown in FIG. 1, the audio signal source 10, the
amplifier device 20, and the speaker devices 30L and 30R are separately configured. It may be
an integrated system (apparatus). Alternatively, correction means (a transformer or the like in the
above example) for correcting the characteristics of the single speaker device may be
incorporated into a single speaker device so that it can be connected to an amplifier device
without a correction processing function. Alternatively, the same correction may be applied to
the audio signal itself output from the audio signal source 10.
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[0037]
Also, for example, by applying the audio reproduction system of this example to a reproduction
system for a so-called car stereo mounted on a vehicle such as an automobile, generally small
noise is easily removed by noise in a reproduction environment where the influence of external
noise is large. The sound of the level is easy to hear and the sound quality is improved.
[0038]
Next, a second embodiment of the present invention will be described with reference to FIG.
In FIG. 5, parts corresponding to FIGS. 1 to 4 described in the first embodiment are given the
same reference numerals.
[0039]
Also in the present embodiment, as in the first embodiment described above, the audio
reproduction system is connected to the speaker device, and is used, for example, in the system
configuration shown in FIG. As a speaker device to be connected, the linearity of the input /
output characteristics of large signals above a predetermined level is substantially maintained,
the linearity of the input / output characteristics is not ensured below the predetermined level,
and the output signal level is inferior to the input signal level. I'm using something.
[0040]
The characteristic correction of the speaker device is also performed in the amplifier device 20
as in the first embodiment. Here, in the present embodiment, the characteristic correction means
is configured differently from the first embodiment.
[0041]
FIG. 5 is a diagram showing a configuration for characteristic correction in the amplifier device
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12
20 of the present example, and shows a connection configuration up to the speaker unit 31
constituting the speaker device 30. As shown in FIG. As shown in FIG. 5, the audio signal
obtained at the audio signal input terminal 21 of the amplifier device is supplied to the amplifier
24 through the buffer amplifier 22 to be amplified for driving the speaker, and the amplified
audio signal is It is supplied to the speaker unit 31 in the speaker device 30 to output (sound off)
an audio signal.
[0042]
Here, an active filter 25 constituted by an active element is connected between the buffer
amplifier 22 and the amplifier 24 as a correction means. The active filter 25 connects a
connection point between the buffer amplifier 22 and the amplifier 24 to one input end of the
operational amplifier 25b via the capacitor 25a, and another operational amplifier 25c between
the output end of the operational amplifier 25b and the other input end. The output end of the
operational amplifier 25 is connected to one input end, and the input end of the operational
amplifier 25c is grounded via a capacitor 25d.
[0043]
The active filter 25 having the configuration shown in FIG. 5 is connected between the buffer
amplifier 22 and the amplifier 24 so that it is less than a predetermined level determined by the
characteristics of the filter in almost all frequency bands of the input audio signal. A correction
process to increase the signal level is performed. The correction characteristics are determined
by the characteristics, the constants, and the like of the elements constituting the active filter 25.
[0044]
Therefore, the audio signal characteristic output from the speaker device 30 connected to the
amplifier device 20 has linearity from low level to high level, in which the insensitivity to the low
level signal of the speaker unit 30 is corrected. It is set to input / output characteristics, and good
audio reproduction can be performed. The characteristic itself to be corrected is the same
principle as the characteristic correction described with reference to FIGS. 3 and 4 in the first
embodiment.
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[0045]
Next, a third embodiment of the present invention will be described with reference to FIG. In FIG.
6, parts corresponding to FIGS. 1 to 5 described in the first and second embodiments are given
the same reference numerals.
[0046]
Also in the present embodiment, as in the first and second embodiments described above, the
audio reproduction system to which the speaker device is connected is used, and is used, for
example, in the system configuration shown in FIG. As a speaker device to be connected, the
linearity of the input / output characteristics of large signals above a predetermined level is
substantially maintained, the linearity of the input / output characteristics is not ensured below
the predetermined level, and the output signal level is inferior to the input signal I'm using
something.
[0047]
The characteristic correction of the speaker device is also performed in the amplifier device 20 in
the same manner as in the first and second embodiments. Here, in the present embodiment, the
characteristic correction means is configured to be different from the first and second
embodiments.
[0048]
FIG. 6 is a view showing a configuration for characteristic correction in the amplifier device 20 of
the present example, and shows a connection configuration up to the speaker unit 31
constituting the speaker device 30. As shown in FIG. As shown in FIG. 6, the audio signal
obtained at the audio signal input terminal 21 of the amplifier device is supplied to the amplifier
24 through the buffer amplifier 22 to be amplified for speaker driving, and the amplified audio
signal is It is supplied to the speaker unit 31 in the speaker device 30 to output (sound off) an
audio signal.
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[0049]
Here, between the buffer amplifier 22 and the amplifier 24, a filter 26 constituted by a passive
element is connected as a correction means. In the filter 26, the connection point between the
buffer amplifier 22 and the amplifier 24 is grounded via the capacitor 26a and the resistor 26b,
and the connection midpoint between the capacitor 26a and the resistor 26b is via the capacitor
26c. It is grounded.
[0050]
Since the filter 26 having the configuration shown in FIG. 6 is connected between the buffer
amplifier 22 and the amplifier 24, a signal of a predetermined level or less determined by the
characteristics of the filter in almost all frequency bands of the input audio signal. A correction
process will be performed to increase the level. The correction characteristics are determined by
the characteristics, the constants, and the like of the elements constituting the filter 26.
[0051]
Therefore, the audio signal characteristic output from the speaker device 30 connected to the
amplifier device 20 has linearity from low level to high level, in which the insensitivity to the low
level signal of the speaker unit 30 is corrected. It is set to input / output characteristics, and good
audio reproduction can be performed. The characteristic itself to be corrected is the same
principle as the characteristic correction described with reference to FIGS. 3 and 4 in the first
embodiment.
[0052]
Next, a fourth embodiment of the present invention will be described with reference to FIG. In
FIG. 7, parts corresponding to those in FIGS. 1 to 6 described in the first, second and third
embodiments are given the same reference numerals.
[0053]
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Also in this embodiment, as in the first, second, and third embodiments described above, the
audio reproduction system to which the speaker device is connected is used, and is used, for
example, in the system configuration shown in FIG. As a speaker device to be connected, the
linearity of the input / output characteristics of large signals above a predetermined level is
substantially maintained, the linearity of the input / output characteristics is not ensured below
the predetermined level, and the output signal level is inferior to the input signal level. I'm using
something.
[0054]
The characteristic correction of the speaker device is also performed in the amplifier device 20
as in the first, second, and third embodiments. Here, in the present embodiment, the
characteristic correction means is configured differently from the first, second, and third
embodiments, and more specifically, the first, second, and third embodiments are described. It is
set as the structure which combined each means demonstrated by form of.
[0055]
That is, as shown in FIG. 7, the audio signal obtained at the audio signal input terminal 21 of the
amplifier device is connected to the primary side of the transformer 23 as the correction means
via the buffer amplifiers 22 and 27. The next side is connected to the amplifier 24, amplified by
the amplifier 24 for driving the speaker, and the amplified audio signal is supplied to the speaker
unit 31 in the speaker device 30, and the audio signal is output (sound emission).
[0056]
Here, between the buffer amplifier 22 and the amplifier 24, an active filter 25 composed of an
active element and a filter 26 composed of a passive element are connected as correction means.
The circuit configurations of the active filter 25 and the filter 26 are the same as the
configurations described in FIG. 5 and FIG.
[0057]
As the configuration shown in FIG. 7 is that the transformer 23, the active filter 25 and the filter
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26 are connected, the correction of the input audio signal is performed with the overall
characteristics of these means 23, 25, 26. In almost all frequency bands of the input audio signal,
a correction process is performed to enhance the signal level below a predetermined level
determined by the characteristics of these means.
[0058]
Therefore, the audio signal characteristic output from the speaker device 30 connected to the
amplifier device 20 has linearity from low level to high level, in which the insensitivity to the low
level signal of the speaker unit 30 is corrected. It is set to input / output characteristics, and good
audio reproduction can be performed.
The characteristic itself to be corrected is the same principle as the characteristic correction
described with reference to FIGS. 3 and 4 in the first embodiment.
[0059]
In the case of this example, since the correction means is constituted by a plurality of circuit
parts (means), the correction characteristics can be finely selected by selecting the characteristics
of each part, etc., and the input / output characteristics of the connected speaker device It is
possible to finely set the correction characteristics in accordance with
[0060]
Next, a fifth embodiment of the present invention will be described with reference to FIG.
In FIG. 8, parts corresponding to FIGS. 1 to 7 described in the first, second, third and fourth
embodiments are given the same reference numerals.
[0061]
Also in this embodiment, as in the above-described embodiments, an audio reproduction system
to which a speaker device is connected is used. For example, the system configuration shown in
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FIG. 1 is used. As a speaker device to be connected, the linearity of the input / output
characteristics of large signals above a predetermined level is substantially maintained, the
linearity of the input / output characteristics is not ensured below the predetermined level, and
the output signal level is inferior to the input signal level. I'm using something.
[0062]
The characteristic correction of the speaker device is also performed in the amplifier device 20,
as in the above-described embodiments. Here, in the present embodiment, the characteristic
correction means is configured to perform digital signal processing.
[0063]
That is, as shown in FIG. 8, the audio signal obtained at the audio signal input terminal 21 of the
amplifier device is supplied to the analog / digital converter 41 to be converted to a digital audio
signal, and the converted digital audio signal is converted to DSP (Digital signal processor) 42 is
supplied. Then, in the digital calculation processing in the DSP 42, the correction processing
described in the first embodiment is performed. That is, for example, all frequency bands in
digital operation processing are divided into signal components above a predetermined level and
signal components below a predetermined level, and no correction processing is performed on
signal components above a predetermined level. Then, for signal components less than a
predetermined level, a curve b (FIG. 3) is not obtained in such a manner that the increase rate
becomes higher than the characteristic a as the output level decreases with respect to the input
level. Correction processing is performed by digital calculation so as to obtain the following
characteristics. Then, the signal component above the predetermined level not subjected to the
correction process and the signal component below the predetermined level subjected to the
correction process are combined, and the combined signal is supplied to the digital / analog
converter 43, and the analog audio signal Convert to
[0064]
The converted analog audio signal is supplied to the amplifier 24, amplified for driving the
speaker, and the amplified audio signal is supplied to the speaker unit 31 in the speaker device
30 to output the audio signal (sound output) Let
[0065]
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In the configuration shown in FIG. 8, correction processing is performed such that a signal level
below a predetermined level determined by the digital processing state is enhanced in almost all
frequency bands of the input audio signal by being corrected by digital processing. become.
[0066]
Therefore, the audio signal characteristic output from the speaker device 30 connected to the
amplifier device 20 has linearity from low level to high level, in which the insensitivity to the low
level signal of the speaker unit 30 is corrected. It is set to input / output characteristics, and good
audio reproduction can be performed.
The characteristic itself to be corrected is the same principle as the characteristic correction
described with reference to FIGS. 3 and 4 in the first embodiment.
[0067]
In the case of this example, since the correction means is configured to perform digital arithmetic
processing, if the correction conditions in the DSP 42 are matched to the input / output
characteristics of the connected speaker device, appropriate correction becomes possible. .
[0068]
In each embodiment described above, although the application to the system for two-channel
audio reproduction shown in FIG. 1 is assumed, it may be configured as a system for multichannel audio reproduction such as 5.1 channel.
[0069]
The installation environment of the speaker device is also applicable to various installation
environments.
For example, the correction in the case of outputting from a so-called speaker device for car
stereo installed in a vehicle such as a car may be performed on the amplifier device side.
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19
[0070]
It is a block diagram showing an example of system composition by a 1st embodiment of the
present invention.
It is a block diagram which shows the structural example by the 1st Embodiment of this
invention.
FIG. 6 is a characteristic diagram showing an example of correction characteristics according to
the first embodiment of the present invention. FIG. 6 is a characteristic diagram showing an
output sensitivity for each frequency showing an example of a correction state according to the
first embodiment of the present invention. It is a block diagram which shows the structural
example by the 2nd Embodiment of this invention. It is a block diagram which shows the
structural example by the 3rd Embodiment of this invention. It is a block diagram which shows
the structural example by the 4th Embodiment of this invention. It is a block diagram which
shows the structural example by the 5th Embodiment of this invention. It is explanatory drawing
which showed the example of an output waveform of the conventional speaker. It is explanatory
drawing which showed the example of the signal level of the conventional speaker. It is
explanatory drawing which showed the output characteristic example (a) of an ideal speaker, and
the output characteristic example (b) of the conventional speaker. It is explanatory drawing
which showed the example of the input-output characteristic of the conventional speaker.
Explanation of sign
[0071]
DESCRIPTION OF SYMBOLS 10 ... Audio signal source, 20 ... Amplifier apparatus, 21 ... Audio
signal input terminal, 22 ... Buffer amplifier, 23 ... Transformer, 24 ... Amplifier, 25 ... Active filter,
26 ... Filter, 27 ... Buffer amplifier, 30, 30L, 30R ... speaker device, 31 ... speaker unit, 41 ... analog
to digital converter, 42 ... DSP (digital signal processor), 43 ... digital to analog converter
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