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JP2013255049

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DESCRIPTION JP2013255049
Abstract: [Problem] To provide a channel divider for changing the reproduction sound quality of
a speaker system by appropriately setting the overlapping of reproduction sounds from a woofer
and a tweeter near a crossover frequency. A channel divider includes a low pass filter and a high
pass filter to which an input speech signal is respectively input, and a lower limit cutoff
frequency and a high to which the input speech signal is input and which is equal to the cutoff
frequency of the low pass filter. A bandpass filter for setting an upper limit cutoff frequency
equal to the cutoff frequency of the bandpass filter, a first multiplier and a second multiplier for
changing and outputting the level of the output of the bandpass filter, and a lowpass filter A first
adder for adding the output and the output of the first multiplier, and a second adder for adding
the high pass filter output and the output of the second multiplier, the output of the first adder
being The output signal is used, and the output of the second adder is used as the second output
signal. [Selected figure] Figure 1
Channel divider and audio reproduction system including the same
[0001]
The present invention relates to a channel divider for use in audio signal reproduction by a multiway speaker system and an audio reproduction system including the same, and in particular,
appropriately setting overlapping of reproduced sound from woofer and tweeter near crossover
frequency. The present invention relates to a channel divider capable of changing the playback
sound quality of a multi-way speaker system.
[0002]
09-05-2019
1
In multi-way speaker systems that include a woofer for low range playback and a tweeter for
high range playback, it is common to include a network circuit that divides the audio signal
amplified by the amplifier according to the playback frequency range of each speaker unit. It is.
In recent years, a network system compatible with a woofer and a network circuit compatible
with a tweeter can be independent of each other, and a speaker system compatible with bi-wiring
connection provided with an input terminal connected to each of the circuits has become
widespread. In the bi-wiring connection, bi-amplifier drive using a power amplifier connected to
the network circuit of the woofer and another power amplifier connected to the network circuit
of the tweeter is adopted.
[0003]
On the other hand, as a method of realizing multi-amplifier (bi-amplifier) driving without using
the network circuit of the speaker system, there is a case where a channel divider is provided in
front of the power amplifier and the audio signal is band divided by this channel divider. In the
audio reproduction system of the multi-amplifier multi-way speaker system as described above,
the channel divider divides the input audio signal into at least a low band output signal and a
high band output signal and outputs it to the multi amplifier Do. By using a channel divider, it is
possible to set an LPF (low-pass filter) or HPF (high-pass filter) having a steeper transition band
than the speaker system network, and to set the crossover frequency relatively freely, etc. (For
example, Patent Document 1). Also, when a channel divider is adopted, the amplifier circuit for
the low band and the amplifier circuit for the high band are independent, so the intermodulation
distortion generated by superposing the low sound component and the high sound component is
reduced, and the reproduction sound quality Is said to have the advantage of being superior.
[0004]
In recent years, there have been attempts to provide a DSP with a channel divider function so
that a speaker system not equipped with a network circuit can be connected using an AV receiver
including a DSP and a multi-amplifier, etc. 3). When the channel divider is realized by a digital
filter, it may be by an FIR filter or an IIR filter. In order to use a channel divider, it is necessary to
set the crossover frequency appropriately by measuring the reproduction band of each speaker
unit of the speaker system using a microphone or the like (Patent Document 4 and Patent
Document 5).
09-05-2019
2
[0005]
In some conventional channel dividers, when a crossover frequency is set between the woofer
and the tweeter, this is automatically applied to the cutoff frequency of the low-pass LPF and the
high-pass HPF. Of course, there are also channel dividers that can independently set the cutoff
frequency of the low-pass LPF and the cutoff frequency of the high-pass HPF. However, in use
conditions that do not use network circuits, the bands that can be reproduced by the woofer and
the tweeter often overlap, so the cutoff frequency of the filter that is in charge of these adjacent
frequency bands is in the overlapping band. It is often set to the same set value of frequency.
[0006]
Also, in conventional channel dividers, the low band LPF and high band HPF can often be
selected from several standard filter characteristics, and the low band LPF and high band HPF It
is often difficult to flexibly adjust the overlapping band of. Examples of standard filter
characteristics include various filters such as Butterworth filter, Bessel filter, Linkwitz-Riley filter,
and the like. In these cases, in the setting of the passband of the filter, the stopband, and the
transition zone between them, the passband of the LPF on the bass side and the passband of the
HPF on the treble side do not overlap. It is common to set filter characteristics that overlap only
in the transition area. Also, even if one filter type is determined, ± 12, ± 24, ... ± 96 dB / Oct. In
some cases, it is possible to select the cutoff characteristic in the transition area such as (octave),
and there are many parameters to be set in the filter characteristic setting conditions.
[0007]
However, in these standard filters, even if the same filter setting is selected by the combination of
the low-pass band LPF and the high-pass band HPF, their addition characteristics may not be flat.
This is the relationship between the LPF's transition area and the HPF's transition area from the
relationship between the filter's gain characteristics and the phase characteristics when the
filter's passband, stopband, and transition area between them are set. This is because the addition
may cause the gain characteristic to be larger or smaller than the gain characteristic of the LPF
passband or the HPF passband. For example, in a filter in which the addition characteristic is flat,
dips may occur at the cutoff frequency when addition is performed in the opposite phase. In
addition, in the case of the Linkwitz-Riley filter, although the addition characteristic of the LPF
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3
and the HPF is always flat, it is only the cutoff frequency of the filter that the output of the LPF
and the output of the HPF become the same level, Even if it is attempted to set a wider
superposition band of the low-pass LPF and the high-pass HPF, ± 24 dB / Oct. In the case of
[0008]
On the other hand, when attempting to realize bi-amplifier driving using a multi-way speaker
system and a channel divider, the setting of the filter characteristics and the setting of the
crossover frequency largely change the reproduction sound quality. This is because, in the
frequency band near the crossover frequency, when the filter characteristics change and the
relative relationship between the audio signal supplied to each of the woofer and the tweeter
changes, the reproduced sound wave from the woofer and the reproduced sound wave from the
tweeter are phase interference in space Because it changes. In general, a tweeter for reproducing
high-pitched sound has a smaller aperture of a speaker diaphragm than a woofer reproducing
bass, and even in the case of reproducing the same frequency, the directional characteristics of
the radiated sound pressure differ due to the difference in diaphragm area. That is, when the
setting of the filter characteristic of the channel divider is changed, the directivity characteristic
which is the synthesis characteristic in the vicinity of the crossover frequency of the multi-way
speaker system changes, and as a result, the reproduction sound quality at the listening point
changes. The channel divider preferably allows various filter characteristics and conditions to be
easily set so as to be able to set the user's preferred playback sound quality.
[0009]
However, without microphones and measuring instruments such as level meters and FFT
analyzers, it is difficult for general users to know the unknown crossover frequency, and for
general users, select appropriate filter settings in the channel divider There is a problem that it is
sometimes difficult to set the crossover frequency. Therefore, in the setting of the filter
characteristics of the channel divider, it is low while satisfying the minimum condition that the
addition characteristics of the LPF on the bass side and the HPF on the treble side are flat near
the crossover frequency of the multiway speaker system. It is preferable to be able to flexibly
adjust the superposition band of the LPF on the side of the sound range and the HPF on the side
of the high sound range. This is because peak dips near the crossover frequency are less likely to
occur at the output level of the channel divider, and audio reproduction under inappropriate
conditions can be avoided.
09-05-2019
4
[0010]
JP, 2005-109969, A JP, 2002-111399, A JP, 2005-184149, A Patent No. 4321315 Japanese
Utility Model Application Publication No. 5-39097
[0011]
The present invention has been made to solve the above-mentioned problems of the prior art,
and its object is to provide a channel divider for use in audio signal reproduction by a multi-way
speaker system, in particular, around the crossover frequency. It is an object of the present
invention to provide a channel divider capable of changing the reproduction sound quality of a
multi-way speaker system by appropriately setting the overlap of reproduction sounds from the
woofer and the tweeter.
[0012]
The channel divider of the present invention divides the input audio signal into at least a first
output signal at the high frequency side and a second output signal at the high frequency side of
the first output signal, and respectively divides the first output signal and the second output
signal. A channel divider that outputs to two output terminals, a low-pass filter and a high-pass
filter to which an input speech signal is input, and a lower limit cut equal to the cutoff frequency
of the low-pass filter to which the input speech signal is input A band pass filter that sets an
upper limit cutoff frequency equal to the off frequency and the cutoff frequency of the high pass
filter, a first multiplier and a second multiplier that change and output the level of the output of
the band pass filter, and a low A first adder that adds the output of the low pass filter and the
output of the first multiplier, and a high pass filter output and the output of the second multiplier
It includes a second adder, and the output of the first adder as a first output signal, the output of
the second adder and the second output signal.
[0013]
Preferably, the channel divider of the present invention comprises a plurality of n band pass
filters in which the band pass filters are band split into a plurality of mutually adjacent frequency
bands, and the first multiplier and the second multiplier are a plurality n The first adder adds the
output of the low pass filter and the outputs of the plurality of n first multipliers, respectively,
and the second adder adds the output of the high pass filter. The output and the outputs of the
plurality of n second multipliers are added.
[0014]
Also preferably, in the channel divider of the present invention, the second multiplier multiplies
the coefficient (1-α) when the first multiplier multiplies the coefficient α (0 ≦ α ≦ 1).
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[0015]
Also preferably, in the channel divider according to the present invention, in the case of the
coefficient α = 0.5, the first output signal on the bass side and the second output signal on the
treble side are respectively determined by corresponding band pass filters. Are equally included.
[0016]
Also preferably, the channel divider of the present invention is configured such that the band
pass filter subtracts the output of the low pass filter that passes two adjacent frequency bands
into the pass band, and the high pass filter is an input It is configured to subtract an audio signal
or a signal obtained by delaying an input audio signal and an output of a low pass filter whose
cutoff frequency is the upper cutoff frequency.
[0017]
Preferably, the channel divider of the present invention comprises a level adjustment circuit for
adjusting the level of the first output signal or the second output signal, and a phase inverting
circuit for performing phase inversion of the first output signal or the second output signal; And
a delay circuit for adjusting a delay time of the first output signal or the second output signal.
[0018]
Further, according to the sound reproduction system of the present invention, there is provided a
speaker system including at least the above channel divider, an amplifier including an
amplification circuit corresponding to each output terminal of the channel divider, a woofer and
a tweeter, and an amplifier and bi-wiring connection. And.
[0019]
Hereinafter, the operation of the present invention will be described.
[0020]
The channel divider of the present invention divides the input audio signal into at least a first
output signal on the high frequency band side and a second output signal on the high frequency
band side of the first output signal, and outputs the first output terminal. And output to the
second output terminal.
09-05-2019
6
The channel divider constitutes an audio reproduction system including an amplifier including an
amplification circuit corresponding to each output terminal of the channel divider, and at least a
woofer and a tweeter, and a speaker system capable of bi-wiring connection with the amplifier. .
Therefore, since the user can adjust the channel divider and change the frequency band in which
the woofer and the tweeter are reproduced in duplicate and the reproduction level thereof, there
is an advantage that it is easy to adjust the reproduction sound quality.
In addition, the network circuit of a general speaker system is ± 6 to 18 dB / Oct.
The channel divider LPFs, BPFs, and HPFs have ± 24 to 96 dB / Oct.
The above-mentioned transition zone characteristics are also possible, and by introducing a
channel divider, the attenuation factor of the transition zone and the stop zone can be increased.
[0021]
The channel divider of the present invention has a lower limit cut-off frequency equal to the cutoff frequency of the low pass filter LPF, which is input with the low pass filter LPF and the high
pass filter HPF to which the input voice signal is input and the input voice signal. And a band
pass filter BPF for setting an upper limit cutoff frequency equal to the cutoff frequency of the
high pass filter HPF, and a first multiplier and a second multiplier for changing and outputting
the level of the output of the band pass filter BPF; A first adder that adds the output of the low
pass filter LPF and the output of the first multiplier, and a second adder that adds the output of
the high pass filter HPF and the output of the second multiplier, An output of the first adder is a
first output signal, and an output of the second adder is a second output signal.
[0022]
That is, the channel divider of the present invention divides the input speech signal into three
frequency bands by the low pass filter LPF, the band pass filter BPF, and the high pass filter HPF,
and between the woofer and the tweeter The cut-off frequency of the filter is set such that the
crossover frequency of is included in the pass band of the band pass filter BPF.
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7
Then, the output of the low pass filter LPF and the output of the band pass filter BPF are added
by a first adder to make a first output signal, and the output of the high pass filter HPF and the
band pass filter BPF is a second adder To add the second output signal.
Therefore, the channel divider of the present invention performs band pass by adjusting the
coefficients by which the first multiplier and the second multiplier multiply the first output signal
on the bass side and the second output signal on the treble side, respectively. To change the
playback sound quality of the multi-way speaker system by being able to add the output
component of the filter BPF and relatively freely adjust the overlap of the playback sound from
the woofer and the tweeter near the crossover frequency Can.
[0023]
The channel divider of the invention preferably causes the second multiplier to multiply the
coefficient (1-.alpha.) When the first multiplier multiplies the coefficient .alpha.
(0.ltoreq..alpha..ltoreq.1).
Only by changing the coefficient α (0 ≦ α ≦ 1) in the first multiplier and the second multiplier,
the band component of the pass band of the band pass filter BPF is reproduced from the woofer
(α = 1) or from the tweeter Reproduction (α = 0) or reproduction from the woofer and tweeter
to the same extent (α = 0.5) can be switched and changed substantially steplessly.
Furthermore, in the case of the coefficient α = 0.5, the predetermined frequency band
component of the corresponding band pass filter BPF is equally included in each of the first
output signal on the bass side and the second output signal on the treble side. It will be.
Therefore, the minimum condition that the addition characteristics of the low-pass LPF and the
high-pass HPF are flat is met, so the overlap between the reproduced sound from the woofer and
the tweeter near the crossover frequency is appropriately set. Can change the playback sound
quality of the multi-way speaker system.
The band to be superimposed may be changed by setting the pass band width (lower limit cutoff
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8
frequency to upper limit cutoff frequency) of the band pass filter BPF including the low pass filter
LPF and the high pass filter HPF.
[0024]
Further, the band pass filter BPF may be composed of a plurality of n band pass filters which are
band divided into a plurality of frequency bands adjacent to each other. In this case, a first
multiplier and a second multiplier are respectively provided at the outputs of the plurality of n
band pass filters, and the first adder is provided with the output of the low pass filter and the
plurality of first multiplications. The second adder adds the output of the high pass filter and the
output of the plurality of n second multipliers. That is, if the band pass filter BPF is configured by
a plurality of n band pass filters BPF1 to BPFn, level adjustment is performed for each band
divided into bands, and reproduction from the woofer (α = 1) or reproduction from the tweeter
(α = 0), or the same degree of reproduction from the woofer and tweeter (α = 0.5) can be
changed. When preparing a plurality of n band pass filters BPF1 to BPFn at intervals of 1⁄6 to
1⁄3 octaves, combining the coefficients α in the respective multipliers and changing them, the
level of the overlapping band Not only the bandwidth of the overlapping band can also be
switched and set substantially by changing only the coefficient α. The user can easily change the
overlap of the playback from the woofer and tweeter around the crossover frequency to change
the playback quality of the multi-way speaker system.
[0025]
Note that the channel divider is configured such that the band pass filter subtracts the output of
the low pass filter that passes two adjacent frequency bands into the pass band, and the high
pass filter is the input voice signal or the input voice signal , And the output of a low pass filter
whose cutoff frequency is the upper cutoff frequency may be subtracted. The channel divider
also includes a level adjustment circuit in which the low pass filter LPF and the high pass filter
HPF perform level adjustment of the first output signal or the second output signal, and phase
inversion of the first output signal or the second output signal. And a delay circuit for adjusting
the delay time of the first output signal or the second output signal, respectively, and the range
for adjusting the reproduction sound quality is expanded, and various multi-way speaker systems
are also included. It becomes possible to cope.
[0026]
The channel divider of the present invention can appropriately set the overlapping of the
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9
reproduced sound from the woofer and the tweeter near the crossover frequency to change the
reproduced sound quality of the multiway speaker system.
[0027]
It is a figure explaining the sound reproduction system containing amplifier device 1 by a
desirable embodiment of the present invention.
(Example 1) Sound pressure frequency characteristics of the speaker system 7 constituting the
sound reproduction system according to a preferred embodiment of the present invention and
frequency characteristics of the low pass filter LPF, the high pass filter HPF, and the band pass
filter BPF Is a graph. (Example 1) It is a graph explaining the output characteristic (The 1st
output signal D1 and the 2nd output signal D2 (in the case of (alpha) = 0.5)) of the channel
divider 12 of the amplifier apparatus 1. FIG. (Example 1) It is a graph explaining the output
characteristic (The 1st output signal D1 and the 2nd output signal D2 (in the case of (alpha) =
1.0)) of the channel divider 12 of the amplifier apparatus 1. FIG. (Example 1) It is a graph
explaining the output characteristic (the 1st output signal D1 and the 2nd output signal D2 (in
the case of alpha = 0)) of channel divider 12 of amplifier device 1. FIG. (EXAMPLE 1) FIG. 6 is a
diagram for explaining another filter configuration of the channel divider 12 of the amplifier
device 1 according to a preferred embodiment of the present invention. (Embodiment 2) FIG. 13
is a table for explaining a combination example of gain coefficients a1 to a4 in the channel
divider 12 of the amplifier device 1. FIG. (Example 2) This is a graph for explaining an example of
the output characteristics (the first output signal D1 and the second output signal D2 (in the case
of the overlapping band of 2 to 4 kHz)) of the channel divider 12 of the amplifier device 1.
(EXAMPLE 2) FIG. 6 is a diagram for explaining another filter configuration of the channel
divider 12 of the amplifier device 1 according to a preferred embodiment of the present
invention. (Example 3)
[0028]
Hereinafter, a channel divider according to a preferred embodiment of the present invention, an
audio reproduction system including the same, and a method of setting a crossover frequency of
the channel divider will be described, but the present invention is not limited to these
embodiments.
[0029]
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10
FIG. 1 is a diagram for explaining a sound reproduction system according to a preferred
embodiment of the present invention.
Specifically, the sound reproduction system includes an amplifier device 1 including a channel
divider, and speaker systems 7L and 7R connected to the amplifier device 1, and FIG. 1 is a block
diagram showing an internal configuration of each. FIG. 2 is a graph for explaining the sound
pressure frequency characteristics of the speaker system 7 and the frequency characteristics of
the low pass filter LPF, the high pass filter HPF, and the band pass filter BPF. 5 is a graph for
explaining output characteristics (a first output signal D1 and a second output signal D2) of a
channel divider of the amplifier device 1. In addition, illustration and description are abbreviate |
omitted about the one part structure unnecessary for description, an internal structure, etc. FIG.
[0030]
The sound reproduction system includes the amplifier device 1 and the speaker systems 7L and
7R connected to the amplifier device 1, converts digital signal data adata input to the amplifier
device 1 into stereo audio signals L and R, and amplifies the amplifier It is an audio reproduction
system which reproduces stereo sound by a speaker system 7 consisting of two speakers 7L and
7R after amplification by 1. The amplifier device 1 includes a DSP and a multi-amplifier, and is
capable of multi-amplifier connection operating a channel divider. The speaker system 7 is a twoway bi-wiring SS including the woofer WO and the tweeter TW, and the amplifier device 1 is biwiring connected by a speaker cord. Therefore, the user using the amplifier device 1 can adjust
the channel divider and change the frequency band in which the woofer and the tweeter play
duplicately and the reproduction level thereof, and can adjust the reproduction sound quality of
the speaker system 7 Become.
[0031]
The amplifier device 1 has a DSP (digital signal processor) 10 that processes digital signal data
adata, a D / A converter 2 that receives outputs of four channels of the DSP 10 and converts
them into analog signals, and analog signals of these And at least an amplifier circuit 3 for
amplifying and outputting to the speaker system 7. The stereo audio signals L and R may be
supplied to the DSP 10 via an A / D converter (not shown) as stereo signals (left signal L and
right signal R) supplied in analog. The amplifier device 1 includes a CPU 4 which is a control
circuit that controls the whole, an operation unit 5 connected to the CPU 4 to receive an
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11
instruction input from a user, and a display circuit 6 including a display. Specifically, the
amplifier device 1 can be configured by a DSP compatible with multi-channel audio, an AV
receiver incorporating a multi-channel amplifier circuit, and the like. The operation unit 5
includes an input device such as a switch, a jog dial, or a remote control device. The display
circuit 6 may be a built-in FL display, a liquid crystal display or the like, or may be a display
device connected to another. Of course, the amplifier device 1 may be configured by another
sound reproducing device including the DSP 10, the D / A converter 2, the multichannel
amplifier circuit 3, and the CPU 4 such as a microcomputer. Also, the DSP 10 included in the
amplifier device 1 may be independent as a single channel divider device.
[0032]
The speaker system 7 is a 2-way bi-wiring SS including the woofer WO and the tweeter TW, and
includes an input terminal corresponding to each speaker unit. The woofer WO for low range
reproduction of the left speaker 7L and the right speaker 7R is connected to the input terminal
tL, and the tweeter TW for high range reproduction is connected to the input terminal tH. Since
the speaker system 7 is a speaker system having no network circuit inside, the DSP 10 included
in the amplifier device 1 configures a channel divider to divide an audio signal into bands, and
outputs the band to the input terminals tL and tH.
[0033]
FIG. 2A is a graph for explaining the sound pressure frequency characteristics of the speaker
system 7. In the woofer WO and the tweeter TW of the speaker system 7 of the present
embodiment, the reproduction frequency band is determined from various conditions such as the
area of the diaphragm. In the case of the speaker system 7, the frequency band for mainly
reproducing the sound is not divided by the network circuit, so the reproduction sound of the
speaker system 7 in the vicinity of the illustrated frequency fc is as shown in FIG. In addition, the
reproduction sound from the woofer WO and the reproduction sound from the tweeter TW will
overlap widely. Therefore, the vicinity of the frequency fc where the woofer WO and the tweeter
TW can reproduce at a similar sound pressure level is suitable as the crossover frequency set by
the channel divider. In this sound reproduction system, the woofer WO for low band
reproduction mainly reproduces the frequency band lower than the crossover frequency fc set by
the channel divider, and the tweeter TW mainly reproduces the frequency band higher than the
crossover frequency fc Do. In the case of a 2-way speaker system, the crossover frequency fc is
generally set between about 1 to 8 kHz.
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[0034]
The DSP 10 internally includes a decoder 11 for converting input data adata into stereo signals L
and R, and a channel divider 12 including a digital filter. The DSP 10 outputs the output
terminals (DL 1, DL 2, DR 1, DR 2) for four channels of the channel divider 12 to the D / A
converter 2. The channel divider 12 includes a low pass filter LPF corresponding to the left signal
L and the right signal R, a band pass filter BPF, a high pass filter HPF, a first multiplier 13 and a
second multiplier 14. It includes a first adder 15, a second adder 16, a first output adjusting
circuit 17, and a second output adjusting circuit 18. The filter settings and the like of the low
pass filter LPF, the band pass filter BPF, and the high pass filter HPF of the channel divider 12 of
the DSP 10 are controlled by the CPU 4.
[0035]
The low pass filter LPF, the band pass filter BPF, and the high pass filter HPF of the channel
divider 12 are digital filters configured by an FIR filter or an IIR filter. The low pass filter LPF, the
band pass filter BPF and the high pass filter HPF are preferably Butterworth filters, LinkwitzRiley filters, etc., and may include linear phase characteristics by an FIR filter. As shown in FIG.
2B, the channel divider 12 divides the input audio signal into three frequency bands by the low
pass filter LPF, the band pass filter BPF, and the high pass filter HPF. In the channel divider 12,
as shown in FIG. 2, the cutoff frequencies of the three filters are set such that the crossover
frequency fc between the woofer WO and the tweeter TW is included in the pass band of the
band pass filter BPF. . Specifically, the lower limit cutoff frequency of the band pass filter BPF is
set equal to the cutoff frequency fl of the low pass filter LPF, and the upper limit cutoff frequency
of the band pass filter BPF is the cutoff of the high pass filter HPF It is set equal to the frequency
fh.
[0036]
The first multiplier 13 and the second multiplier 14 change the level of the output of the band
pass filter BPF and output it. The first multiplier 13 multiplies the output of the band pass filter
BPF by the coefficient α (0 ≦ α ≦ 1), and outputs the result to the first adder 15. The second
multiplier 14 multiplies the output of the band pass filter BPF by the coefficient (1−α) and
outputs the result to the second adder 16. The first adder 15 adds the output of the low pass
filter LPF and the output of the band pass filter BPF multiplied by the coefficient α, and inputs
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the result to the first output adjustment circuit 17 as a first audio output signal D1. Output to the
output terminals (DL1, DR1) of the DSP 10. The second adder 16 adds the output of the low pass
filter LPF and the output of the band pass filter BPF multiplied by the coefficient (1-α) and
inputs the result to the second output adjustment circuit 18, The voice output signal D2 is output
to the output terminals (DL2, DR2) of the DSP 10. The first output adjustment circuit 17 and the
second output adjustment circuit 18 expand the range for adjusting the reproduction sound
quality to be compatible with the wide speaker system 7, the first audio output signal D1 and the
second audio output signal D2 Each includes a level adjustment circuit that performs level
adjustment, a phase inversion circuit that performs phase inversion, and a delay circuit that
adjusts delay time.
[0037]
During normal sound reproduction, the channel divider 12 provides a band pass filter BPF
corresponding to the crossover frequency band of the speaker system 7 between the low pass
filter LPF and the high pass filter HPF as shown in FIG. The adjustment of how much the output
of this band pass filter BPF is added to the output of the low pass filter LPF or the high pass filter
HPF is adjusted. That is, the output component of the band pass filter BPF is adjusted by adding
only one coefficient α to each of the first audio output signal D1 on the low frequency side and
the second audio output signal D2 on the high frequency side, It is possible to change the
reproduced sound quality of the multi-way speaker system by relatively freely adjusting the
overlapping of the reproduced sound from the woofer and the tweeter near the over frequency.
[0038]
3 shows the output characteristics of the channel divider 12 of the amplifier device 1 when the
coefficient α of the first multiplier 13 is 0.5 (FIG. 3 (a): second audio output signal D2, FIG. 3 (b):
It is a graph explaining 1st audio | voice output signal D1). The output characteristic of the first
audio output signal D1 is such that the output level of the pass band below the cutoff frequency
f1 is 0 dB and the output level of the pass band is band-limited to the frequencies fl to fh. The
output of the 6 dB band pass filter BPF and the step characteristic shown in the figure are added,
and the cutoff frequency fh or more is the stop band. On the other hand, the output characteristic
of the second audio output signal D2 is band-limited to the output of the high pass filter HPF
whose output level in the passband above the cutoff frequency fh is 0 dB and the frequency fl to
fh. The output of the band pass filter BPF having a level of -6 dB and the step characteristic as
shown in the figure is added, and the cutoff frequency fl or less is the stop band.
09-05-2019
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[0039]
As described above, when the coefficient α is 0.5, the predetermined frequency of the band pass
filter BPF corresponding to each of the first audio output signal D1 on the low band side and the
second audio output signal D2 on the high band side The band components are equally included,
and the superposition band of the first audio output signal D1 on the low band side and the
second audio output signal D2 on the high band side is intentionally set wider than that of other
conventional filters. be able to. When the sound pressure level level of the reproduced sound
wave from the woofer WO and the sound wave level from the tweeter TW is wide, the phase
interference of the sound wave in space widens, so the directivity characteristic of the speaker
system changes and the reproduction sound quality Change. Further, in the channel divider 12, a
flat 0 dB gain characteristic can be obtained by adding the first audio output signal D1 on the low
frequency side and the second audio output signal D2 on the high frequency side. Therefore, in
the vicinity of the crossover frequency fc of the speaker system 7, the gain characteristic does
not increase or decrease, and the superposition band of the LPF on the bass side and the HPF on
the treble side can be flexibly adjusted. .
[0040]
FIG. 4 shows the output characteristic of the channel divider 12 of the amplifier device 1 when
the coefficient α of the first multiplier 13 is 1.0 (FIG. 4 (a): second audio output signal D2, FIG. 4
(b): It is a graph explaining 1st audio | voice output signal D1). The output characteristic of the
first audio output signal D1 is such that the output level in the pass band below the cutoff
frequency fl is 0 dB and the output level of the low pass filter LPF is 0 dB and the output level in
the pass band is 0 dB And the output of the band pass filter BPF as shown in the figure, and the
cutoff frequency fh or more is the stop band. On the other hand, the output characteristic of the
second audio output signal D2 has a characteristic as shown in the figure only of the output of
the high pass filter HPF whose output level in the pass band above the cutoff frequency fh is 0
dB, the cutoff frequency fh The following is the stop zone.
[0041]
Further, FIG. 5 shows an output characteristic of the channel divider 12 of the amplifier device 1
when the coefficient α of the first multiplier 13 is 0 (FIG. 5 (a): second audio output signal D2,
FIG. 5 (b): It is a graph explaining 1st audio | voice output signal D1). The output characteristic of
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the first audio output signal D1 has the characteristic shown in the figure only of the output of
the low pass filter LPF whose output level in the pass band below the cutoff frequency f is 0 dB,
and the cutoff frequency f or higher is blocked Area. On the other hand, the output characteristic
of the second audio output signal D2 is band-limited to the output of the high pass filter HPF
whose output level in the passband above the cutoff frequency fh is 0 dB and the frequency fl to
fh. The output of the band pass filter BPF having a level of 0 dB and the characteristic shown in
the figure are added, and the cutoff frequency fl or less is the stop band.
[0042]
As described above, when the coefficient α is 1.0 or 0, the predetermined frequency band
component of the band pass filter BPF is only the first voice output signal D1 on the bass side or
the second voice on the treble side. Only the output signal D2 is included. The coefficient α is set
by the CPU 4 controlling the DSP 10 and changing it in the range of 0 or more and 1 or less,
between the first audio output signal D1 on the low frequency range and the second audio
output signal D2 on the high frequency range, The superposition band corresponding to the
crossover frequency band of the speaker system 7 can be intentionally adjusted and set to be
distributed more, equal, or less to either the woofer WO or the tweeter TW. In this channel
divider 12, a flat 0 dB gain characteristic can be obtained by adding the first audio output signal
D1 on the low frequency range side and the second audio output signal D2 on the high frequency
range side. Therefore, when the user operates the operation unit 5 by looking at the display
circuit 6 including the display, when the CPU 4 controls the DSP 10 to change the coefficient α
in the range of 0 or more and 1 or less, the substantial crossover of the speaker system 7 The
frequency fc can be changed between the frequencies fl to fh.
[0043]
As in this embodiment, when the cutoff frequencies fl and fh are set so that the crossover
frequency fc settable by the speaker system 7 is included in the pass band of the band pass filter
BPF in the channel divider 12, a basic speaker The sound pressure frequency characteristics of
the system 7 can be adjusted without changing and changing the reproduction sound quality of
the superposition band of the sound reproduction system. For example, when stereo sound is
reproduced in the 2 way speaker system 7, since the reproduction band of the vocal sound of the
singer exists so as to cross the crossover frequency fc, the steep transition area characteristic is
set by the channel divider 12, the woofer WO The interference between the playback sound wave
of tweezers and the sound wave of tweeter TW is substantially reduced, and the sound image is
such that the user makes the singer's vocal size smaller than when channel divider 12 is not
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functioning. You can get a feeling. On the other hand, as in the present embodiment, if it is
possible to intentionally adjust the interference between the reproduced sound wave of the
woofer WO and the reproduced sound wave of the tweeter TW, the user simply points the
speaker system 7 only by changing the coefficient α. The characteristics can be adjusted to
obtain a desired sound image feeling. Of course, it is preferable that the cutoff frequency of the
low pass filter LPF, the band pass filter BPF, and the high pass filter HPF of the channel divider
12 can be set finely, for example, according to JIS standard (or ISO / IEC standard) It may be set
in steps of about 1/3 octave or about 1/6 octave. Further, it is preferable that the band pass of
the band pass filter BPF can be freely set in the range of about 1/6 to 4 octaves.
[0044]
However, the channel divider 12 is not limited to the one applied to the 2-way bi-wiring SS
including the woofer WO and the tweeter TW as in the above embodiment. Channel divider 12 is
a 3-5 way multi-way speaker (not shown) that is a 3-5 way multi-way speaker including
subwoofers and / or midranges and / or super tweeters, 3-5 for 3-5 ways It may be configured to
include band-divided output. Further, the band pass filter BPF may be configured by connecting
another high pass filter HPF or another low pass filter LPF in series to the low pass filter LPF and
the high pass filter HPF.
[0045]
Of course, the channel divider 12 of this embodiment is also effective in the case of a multi-way
speaker including a woofer and a tweeter including a network circuit. Also, when the speaker
system 7 includes a full range speaker, the channel divider 12 is similarly effective. Even when
the substantial crossover frequency fc with other speakers is set corresponding to the level
reduction due to the limit of the reproduced sound pressure frequency characteristic of the full
range speaker or the speaker such as the woofer or tweeter. The band pass filter BPF of the
channel divider 12 can be set according to this.
[0046]
FIG. 6 is a diagram for explaining another filter configuration of the channel divider 12 of the
amplifier device 1 of the above embodiment. FIG. 7 is a table for explaining a combination
example of the gain coefficients a1 to a4 in the channel divider 12. Furthermore, FIG. 8 is a
09-05-2019
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graph for explaining an example of the output characteristics (the first output signal D1 and the
second output signal D2 (in the case of the superimposed band 2k to 4 kHz)) of the channel
divider 12 of the amplifier device 1. The filter configurations on the left signal L side and the
right signal R side are the same, so only one side is shown and the illustration and description on
the other side are omitted.
[0047]
In the channel divider 12 of the amplifier device 1 of this embodiment, the cutoff frequency fl of
the low pass filter LPF is set to 1.6 kHz, and the cutoff frequency fh of the high pass filter HPF is
set to 4 kHz, and the band pass filter The pass band of BPF is set to 1.6 kHz to 4 kHz. Therefore,
the user can set the crossover frequency fc of the speaker system 7 which is the bi-wiring SS in
the range of 1.6 kHz to 4 kHz. Furthermore, the band pass filter BPF is 1/3 Oct. The four band
pass filters BPF1 to BPF4 are divided into four frequency bands adjacent to each other at an
(octave) interval. BPF 1 has a pass band of 1.6 k to 2 kHz, BPF 2 of 2 k to 2.5 kHz, BPF 3 of 2.5 k
to 3.2 kHz, and BPF 4 of 3.2 k to 4 kHz.
[0048]
A first multiplier 13 and a second multiplier 14 are provided at the outputs of the band pass
filters BPF1 to BPF4, respectively. The coefficients a1 to a4 in these first multipliers 13 are
values of 0 or more and 1 or less, respectively, and can be changed independently of each other.
Further, the second multiplier 14 is a numerical value obtained by subtracting the coefficients a1
to a4 in the corresponding first multiplier 13 from one. Furthermore, the first adder 15 adds the
output of the low pass filter LPF and the output of the four first multipliers 13. Also, the second
adder 16 adds the output of the high pass filter HPF and the output of the four second
multipliers 14. The first output adjustment circuit 17 and the second output adjustment circuit
18 respectively include a level adjustment circuit that performs level adjustment, a phase
inversion circuit that performs phase inversion, and a delay circuit that adjusts a delay time.
[0049]
As shown in FIGS. 7 and 8, in the channel divider 12 of this embodiment, the band pass filter BPF
is configured of four band pass filters BPF1 to BPF4, and the level adjustment is performed for
each band divided into bands, and the woofer Reproduction from WO (coefficient a1 to a4 = 1) or
09-05-2019
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reproduction from tweeter TW (coefficient a1 to a4 = 0), or reproduction from Woofer WO and
tweeter TW to the same extent (coefficient a1 to a4 = 0.5) Or you can change the balance and
play from both sides. For example, with the combination of the coefficients a1 to a4 of the first
multiplier 13 as shown in the table of FIG. 7A, the cutoff frequency can be set without providing
a superimposed band reproduced from both the woofer WO and the tweeter TW. This can be
switched at 1/3 octave intervals. For example, when the coefficients a1 = 1 and a2 = a3 = a4 = 0,
the substantial crossover frequency fc of the speaker system 7 can be set to 2 kHz without
providing the overlapping band. Further, when the coefficients a1 = a2 = 1 and a3 = a4 = 0, the
substantial crossover frequency fc of the speaker system 7 can be set to 2.5 kHz without
providing the overlapping band.
[0050]
Next, with the combination of the coefficients a1 to a4 of the first multiplier 13 as shown in the
table of FIG. 7 (b), it is possible to provide a 1/3 octave overlapping band reproduced from both
the woofer WO and the tweeter TW. . That is, in the table of FIG. 7B, when any one of the band
pass filters BPF1 to BPF4 is set as the overlapping band, the coefficients a1 to a4 of the
corresponding first multiplier 13 are set to 0.5, The coefficients of the other first multipliers 13
may be set to 1 or 0. Further, in the combination of the coefficients a1 to a4 of the first multiplier
13 as shown in the table of FIG. 7C, the superposition band reproduced from both the woofer
WO and the tweeter TW is one octave (= 1/3 oct. × 3 bands) can be extended. For example, as
described in the left column of the table of FIG. 7C, the coefficient a4 of the first multiplier 13 of
the band pass filter BPF4 is set to 0, and the coefficients a1 to a3 of the other first multiplier 13
are set to 0. If set to .5, the band components of the superimposed band 1.6 k to 3.2 kHz can be
equally included in the first output signal D1 and the second output signal D2.
[0051]
On the other hand, as described in the right column of the table of FIG. 7C, the coefficient a1 of
the first multiplier 13 of the band pass filter BPF1 is set to 1, and the coefficients a2 and a4 of
the other first multiplier 13 are set. Is set to about 0.3, and the coefficient a3 of the remaining
first multiplier 13 is set to 0.5, as shown in FIG. 8, the overlapping bands of the first output
signal D1 and the second output signal D2 are obtained. It is possible to meet the condition of
intentionally changing the balance of 1.6 k to 3.2 kHz and making the addition characteristic flat.
In the case of the coefficient switching shown in FIGS. 7 and 8, this is only an example, and the
user using the channel divider 12 can easily overlap the reproduced sound from the woofer WO
and the tweeter TW in the vicinity of the crossover frequency fc. The combination of coefficients
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of the multiplier 13 can be changed to change the reproduction sound quality of the speaker
system 7. Although the band pass filter BPF is divided into four bands in the above embodiment,
it may be divided into 3 to 12 bands when the frequency band is expanded or the width of the
divided bands is narrowed.
[0052]
In the present embodiment, not only the level of the overlapping band of the channel divider 12
but also the bandwidth of the overlapping band can be switched and set substantially by
changing only the coefficient α. That is, if the band division characteristics are changed by
combining the coefficients a1 to a4 in the respective first multipliers 13, the filter characteristics
of the low pass filter LPF, the band pass filter BPF, and the high pass filter HPF There is an
advantage that it is almost unnecessary to mute the output sound every time the filter
characteristics are changed, and the audition confirmation can be performed in real time.
Therefore, the user operates the channel divider 12 to change the substantial crossover
frequency fc while reproducing the synthesized sound of the sound reproduced from the woofer
WO of the speaker system 7 and the sound reproduced from the tweeter TW. The sound quality
can be finely adjusted.
[0053]
FIG. 9 is a diagram for explaining another filter configuration of the channel divider 12 of the
amplifier device 1 of the above embodiment. The channel divider 12 of this embodiment is
common except that the specific configurations of the band pass filter BPF and the high pass
filter HPF are different from those of the previous embodiments. Therefore, the description of the
common parts is omitted.
[0054]
The channel divider 12 of this embodiment is the same as the previous embodiment in that the
band pass filter BPF is composed of four band pass filters BPF1 to BPF4. However, the bandpass
filter BPF1 having a passband of 1.6 kHz to 2 kHz is lower than the output of the low pass filter
LPF1 whose cutoff frequency fl is set to 2 kHz and the cutoff frequency fl is set to 1.6 kHz. It is
configured to subtract the output of the low pass filter LPF. Similarly, the bandpass filter BPF2
having a passband of 2 kHz to 2.5 kHz has a cutoff frequency fl set to 2 kHz from the output of
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the low pass filter LPF2 whose cutoff frequency fl is set to 2.5 kHz. The output of the low pass
filter LPF1 is configured to be subtracted.
[0055]
Similarly, the band pass filter BPF3 having a pass band of 2.5 kHz to 3.2 kHz has a cutoff
frequency fl of 2.5 kHz from the output of the low pass filter LPF3 whose cutoff frequency fl is
set to 3.2 kHz. Is configured to subtract the output of the low pass filter LPF2 set to. Similarly,
the bandpass filter BPF4 having a passband of 3.2 kHz to 4 kHz has a cutoff frequency fl set to
3.2 kHz from the output of the low pass filter LPF4 having a cutoff frequency fl set to 4 kHz. It is
configured to subtract the output of the low pass filter LPF3.
[0056]
Further, the high pass filter HPF is configured to subtract the signal obtained by delaying the
input voice signal by the delay circuit Delay and the output of the low pass filter LPF 4 having a
cutoff frequency fl of 4 kHz. The delay time of the delay circuit Delay is set equal to the delay
time of the FIR linear phase filter that constitutes the low pass filter LPF4. In this way, the filter
configuration of the channel divider 12 can be simplified. When the low pass filter LPF4 is
formed of a non-linear phase IIR filter, the input audio signal may be subtracted from the output
of the low pass filter LPF4 without providing a delay circuit. Good. The low pass filter LPF may be
configured to subtract the signal obtained by delaying the input voice signal by the delay circuit
Delay and the output of the other high pass filter HPF.
[0057]
Further, the configuration including the first multiplier 13 and the second multiplier 14 of the
channel divider 12 is not limited to the configuration described and illustrated in the above
embodiment. That is, the coefficient to be multiplied by the second multiplier 14 with the
coefficient α to be multiplied by the first multiplier 13 may not be limited to the case of (1−α).
That is, the output of the low pass filter LPF and the output of the band pass filter BPF are added
by the first adder 15 to form a first output signal, and the output of the high pass filter HPF and
the band pass filter BPF is added second What is necessary is just to add by the unit 16 to make
a second output signal, and to provide both predetermined overlapping bands. The user can
easily change the overlap of the playback from the woofer and tweeter around the crossover
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frequency to change the playback quality of the multi-way speaker system.
[0058]
The channel divider of the present invention is applicable not only to stereo devices that
reproduce stereo audio signals, but also to sound reproduction systems that include multichannel surround sound reproduction devices.
[0059]
REFERENCE SIGNS LIST 1 amplifier device 2 D / A converter 3 amplifier circuit 4 CPU 5
operation unit 6 display circuit 7 speaker system 10 DSP 11 decoder 12 channel divider
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