JP2013255050A - Channel divider and audio reproduction system including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a channel divider that can change reproduced sound quality of a multiway speaker system by appropriately setting an overlap of reproduced sounds from a woofer and a tweeter in the vicinity of a crossover frequency.SOLUTION: The channel divider comprises: a low pass filter and a high pass filter; a bandpass filter for setting a lower limit cutoff frequency equal to a cutoff frequency of the low pass filter and an upper limit cutoff frequency equal to a cutoff frequency of the high pass filter; a first comb filter and a second comb filter for receiving an output of the bandpass filter; a first adder for adding an output of the low pass filter and an output of the first comb filter; and a second adder for adding an output of the high pass filter and an output of the second comb filter. An output of the first adder is a first output signal, and an output of the second adder is a second output signal.

Description

  The present invention relates to a channel divider used for audio signal reproduction by a multi-way speaker system and an audio reproduction system including the channel divider. In particular, the overlap of reproduced sounds from a woofer and a tweeter near the crossover frequency is appropriately set. The present invention relates to a channel divider that can change the playback sound quality of a multi-way speaker system.

  In a multi-way speaker system including a woofer for low-frequency range playback and a tweeter for high-frequency range playback, it is common to include a network circuit that divides the audio signal amplified by the amplifier in accordance with the playback frequency band of each speaker unit. It is. In recent years, a network system corresponding to a woofer and a network circuit corresponding to a tweeter can be independent of each other, and a speaker system corresponding to a bi-wiring connection provided with an input terminal connected to each of them has become widespread. In bi-wiring connection, bi-amp driving 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.

  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 divided into bands by this channel divider. In the audio playback 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-frequency side output signal and a high-frequency side output signal and outputs it to the multi-amplifier. To do. By using a channel divider, LPF (low-pass filter) or HPF (high-pass filter) having a steeper transition band than the network of the speaker system can be set, the crossover frequency can be set relatively freely, etc. (For example, patent document 1). In addition, when a channel divider is used, the low-frequency amplifier circuit and the high-frequency amplifier circuit are independent, reducing the cross-modulation distortion that occurs when the low-frequency component and the high-frequency component are superimposed, reducing the playback sound quality. It is said that there is an advantage that it is excellent.

  In recent years, there has been an attempt to give a DSP a channel divider function so that a speaker system without a network circuit can be connected using an AV receiver including a DSP and a multi-amplifier (Patent Document 2, Patent Document). 3). When the channel divider is realized by a digital filter, an FIR filter or an IIR filter may be used. In order to use the channel divider, it is necessary to appropriately set the crossover frequency by measuring the reproduction band of each speaker unit of the speaker system using a microphone or the like (Patent Documents 4 and 5).

  In some conventional channel dividers, when a crossover frequency is set between a woofer and a tweeter, this is automatically applied to the cut-off frequency between the low-frequency LPF and the high-frequency HPF. Of course, there is also a channel divider that can independently set the cutoff frequency of the LPF on the low sound side and the cutoff frequency of the HPF on the high sound side. However, since the bands that can be reproduced by the woofer and the tweeter are often duplicated under the use conditions without using the network circuit, the cutoff frequency of the filter that handles these adjacent frequency bands is the above-mentioned overlapping band. Often set to the same frequency setting.

  Also, in the conventional channel divider, the LPF on the low frequency side and the HPF on the high frequency side can be selected from several standard filter characteristics, and the LPF on the low frequency range and the HPF on the high frequency range side can be selected. In many cases, it is difficult to flexibly adjust the superimposing band. Specific examples of standard filter characteristics include various filters such as a Butterworth filter, a Bessel filter, and a Linkwitz-Riley filter. In these cases, in setting the pass band of the filter, the stop band, and the transition band between them, the low pass LPF pass band and the high pass HPF pass band do not overlap. It is common to set filter characteristics that are duplicated only in the transition region. Even if one filter type is determined, ± 12, ± 24,... ± 96 dB / Oct. There are cases where the cutoff characteristic in the transition region such as (octave) can be selected, and there are many parameters to be set as the filter characteristic setting conditions.

  However, in these standard filters, even when the same filter setting is selected for the combination of the LPF on the low sound region side and the HPF on the high sound region side, the addition characteristic thereof does not include a flat characteristic. This is because when the filter pass band, the stop band, and the transition band between them are set, the characteristics of the LPF transition band and the HPF transition band are determined from the relationship between the gain characteristics and phase characteristics of the filter. This is because the sum may be larger or smaller than the gain characteristics of the LPF passband or HPF passband. For example, in a filter having a flat addition characteristic, if the addition is performed in reverse phase, a dip may occur at the cutoff frequency. In addition, in the case of the Linkwitz-Riley filter, the LPF and HPF addition characteristics are always flat, but the LPF output and the HPF output are the same level only in the cutoff frequency of the filter. Even if an attempt is made to set a wider overlap band between the LPF on the low sound side and the HPF on the high sound side, ± 24 dB / Oct. It is only the maximum in the case of.

  On the other hand, when the bi-amplifier drive is realized using the multi-way speaker system and the channel divider, the reproduction sound quality greatly changes depending on the setting of the filter characteristic and the setting of the crossover frequency. This is because when the filter characteristics change in the frequency band near the crossover frequency and the relative relationship between the audio signals supplied to the woofer and the tweeter changes, the reproduced sound wave from the woofer and the reproduced sound wave from the tweeter interfere in phase in space. Because it changes. A tweeter that reproduces a high sound range generally has a smaller speaker diaphragm diameter than a woofer that reproduces a low sound range, and even when reproducing the same frequency, the directional characteristics of the radiation sound pressure are different due to the difference in the area of the diaphragm. That is, if the setting of the filter characteristic of the channel divider is changed, the directional characteristic that is the combined characteristic near the crossover frequency of the multi-way speaker system changes, and as a result, the reproduced sound quality at the listening point changes. It is preferable that the channel divider can easily set various filter characteristics and conditions so that the reproduction sound quality preferred by the user can be set.

  However, without a microphone, level meter, FFT analyzer, or other measuring device, it is difficult for the general user to know the unknown crossover frequency. For the general user, the appropriate filter setting is selected by the channel divider. Or, there is a problem that it may be difficult to set the crossover frequency. Therefore, in setting the filter characteristics of the channel divider, while satisfying the minimum condition of flattening the addition characteristics of the LPF on the low frequency side and the HPF on the high frequency side near the crossover frequency of the multiway speaker system, It is preferable that the overlapping band of the LPF on the sound range side and the HPF on the high sound range side can be adjusted flexibly. 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.

JP 2005-109969 A JP 2002-111399 A JP 2005-184149 A Japanese Patent No. 4321315 Japanese Utility Model Publication No. 5-39097

  The present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is a channel divider used for reproducing an audio signal by a multi-way speaker system, particularly in the vicinity of a crossover frequency. It is an object of the present invention to provide a channel divider that can change the reproduction sound quality of a multi-way speaker system by appropriately setting the overlap of reproduction sounds from woofers and tweeters.

  The channel divider according to the present invention divides an input audio signal into at least a first output signal on the low frequency range side and a second output signal on the high frequency range side than the first output signal, and the first output terminal and the first output signal respectively. A channel divider that outputs to two output terminals, a low-pass filter and a high-pass filter that each receive an input audio signal, and a lower limit cut that is equal to the cut-off frequency of the low-pass filter that receives the input audio signal 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 comb filter that receives the output of the band-pass filter, and a first that receives the output of the band-pass filter Two comb filters, a first adder for adding the output of the low-pass filter and the output of the first comb filter, and a high-pass filter It includes a second adder for adding the output of the output and a second comb filter, and the output of the first adder as a first output signal, the output of the second adder and the second output signal.

  Preferably, the channel divider according to the present invention is configured such that the first comb filter and the second comb filter output signals that are 90 ° out of phase and uncorrelated with each other, and the outputs of the first and second comb filters are added to each other. It includes a multiplier that adjusts the level so that the output of the pass filter is reproduced.

  Preferably, in the channel divider according to the present invention, the first comb filter is configured to delay the output signal of the input band-pass filter by branching and delay the output signal of the band-pass filter and the output signal of the delay circuit. And a second comb filter configured to include a delay circuit and a subtracter that subtracts the output signal of the delay circuit from the output signal of the bandpass filter.

  Preferably, in the channel divider of the present invention, the delay time set by the delay circuit appears at the lowest dip frequency appearing in the output characteristics of the first comb filter or in the output characteristics of the second comb filter. The lowest peak frequency is set so that the cut-off frequency of the high-pass filter matches.

  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 makes two adjacent frequency bands pass, and the high pass filter is the input The audio signal or the signal obtained by delaying the input audio signal is subtracted from the output of the low-pass filter having the upper limit cutoff frequency as the cutoff frequency.

  Preferably, the channel divider according to the present invention includes a level adjustment circuit for adjusting a level of the first output signal or the second output signal, a phase inversion circuit for performing phase inversion of the first output signal or the second output signal, A delay circuit for adjusting a delay time of the first output signal or the second output signal.

  In addition, the sound reproduction system of the present invention includes a speaker system that includes at least the above-described channel divider, an amplifier including an amplifier circuit corresponding to each output terminal of the channel divider, and a woofer and a tweeter and is capable of bi-wiring connection with the amplifier. And including.

  The operation of the present invention will be described below.

  The channel divider according to the present invention divides the input audio signal into at least a first output signal on the low frequency range side and a second output signal on the high frequency range side than the first output signal, and each of the first output terminals. And output to the second output terminal. The channel divider constitutes an acoustic reproduction system including an amplifier including an amplifier 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, the user can adjust the channel divider to change the frequency band and the reproduction level in which the woofer and the tweeter are reproduced in an overlapping manner, so that there is an advantage that the reproduction sound quality can be easily adjusted. The network circuit of a general speaker system is ± 6 to 18 dB / Oct. The channel divider LPF, BPF, and HPF are ± 24 to 96 dB / Oct. The above transition region characteristics are also possible, and by introducing a channel divider, the attenuation rate of the transition region and the stop region can be increased.

  The channel divider of the present invention includes a low-pass filter and a high-pass filter to which an input audio signal is input, respectively, a lower-limit cutoff frequency and a high-frequency that are input to the input audio signal and are equal to the cutoff frequency of the low-pass filter A bandpass filter that sets an upper cutoff frequency equal to the cutoff frequency of the pass filter, a first comb filter that receives the output of the bandpass filter, a second comb filter that receives the output of the bandpass filter, A first adder for adding the output of the low-pass filter and the output of the first comb filter; and a second adder for adding the output of the high-pass filter and the second comb filter. Is the first output signal, and the output of the second adder is the second output signal.

  That is, the channel divider of the present invention 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, and between the woofer and the tweeter. The cut-off frequency of the filter is set so that the crossover frequency is included in the passband of the bandpass filter BPF. Then, the output of the band pass filter is input to the first comb filter and the second comb filter, and the output of the low pass filter LPF and the output of the band pass filter BPF that has passed through the first comb filter are input by the first adder. The first output signal is added, and the high pass filter HPF and the output of the band pass filter BPF that has passed through the second comb filter are added by the second adder to obtain the second output signal. Therefore, the channel divider of the present invention can add the output component of the band-pass filter BPF that has passed through the comb filter to each of the first output signal on the low frequency range side and the second output signal on the high frequency range side. The reproduction sound quality of the multi-way speaker system can be changed by relatively freely adjusting the overlap of the reproduction sounds from the woofer and the tweeter near the over frequency.

  The channel divider according to the present invention is preferably configured such that the first comb filter and the second comb filter output signals that are 90 ° out of phase and uncorrelated with each other, and the respective outputs are added together. It includes a multiplier that adjusts the level so that the output of the pass filter is reproduced. That is, the output of the first comb filter and the second comb filter have an uncorrelated relationship in which the output of the flat band-pass filter is reproduced regardless of whether they are added or subtracted. Therefore, the minimum condition of flattening the addition characteristics of the low frequency range LPF and the high frequency range HPF is satisfied, and the phase relationship between the woofer and the tweeter is not related to the normal phase or the reverse phase. The reproduction sound quality of the multi-way speaker system can be changed by appropriately setting the overlap of the reproduction sounds from the woofer and tweeter in the system. The band to be superimposed may be changed by setting the pass band width (lower limit cutoff frequency to upper limit cutoff frequency) of the band pass filter BPF including the low pass filter LPF and the high pass filter HPF.

  The first comb filter may include a delay circuit that branches and delays the output signal of the input bandpass filter, and an adder that adds the output signal of the bandpass filter and the output signal of the delay circuit. The second comb filter may be configured to include a delay circuit and a subtracter that subtracts the output signal of the delay circuit from the output signal of the bandpass filter. Specifically, the delay time set by the delay circuit is the lowest dip frequency that appears in the output characteristics of the first comb filter, or the lowest peak frequency that appears in the output characteristics of the second comb filter, It may be set so that the cut-off frequency of the pass filter matches. The configuration of the first comb filter and the second comb filter can be simplified, and a natural roll-off characteristic using the characteristics of the comb filter can be added to the first output signal and the second output signal. The user can easily change the playback sound quality of the multi-way speaker system by changing the overlap of the playback sound from the woofer and tweeter near the crossover frequency.

  The channel divider is configured such that the band-pass filter subtracts the output of the low-pass filter that makes two adjacent frequency bands pass, and the high-pass filter is the input audio signal or the input audio signal. May be configured to subtract the signal delayed from the output of the low-pass filter having the upper limit cutoff frequency as the cutoff frequency. The channel divider includes a level adjustment circuit in which the low pass filter LPF and the high pass filter HPF adjust the level of the first output signal or the second output signal, and the 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, and the range for adjusting the reproduction sound quality is widened, and can be applied to various multi-way speaker systems. It becomes possible to respond.

  The channel divider of the present invention can change the reproduction sound quality of the multi-way speaker system by appropriately setting the overlap of the reproduction sounds from the woofer and the tweeter near the crossover frequency.

It is a figure explaining the sound reproduction system containing the amplifier apparatus 1 by preferable embodiment of this invention. Example 1 It is a graph explaining the sound pressure frequency characteristic of the speaker system 7 which comprises the sound reproduction system by preferable embodiment of this invention, and the frequency characteristic of the low-pass filter LPF, the high-pass filter HPF, and the band-pass filter BPF. Example 1 It is a figure explaining the filter structure of the channel divider 12 of the amplifier apparatus 1 by preferable embodiment of this invention. Example 1 6 is a graph for explaining gain frequency characteristics and phase frequency characteristics of a first comb filter COM1 and a second comb filter COM2 of the channel divider 12 of the amplifier device 1. Example 1 6 is a graph for explaining output characteristics (first output signal D1 and second output signal D2) of the channel divider 12 of the amplifier device 1; Example 1 It is a figure explaining the other filter structure of the channel divider 12 of the amplifier apparatus 1 by preferable embodiment of this invention. (Example 2)

  Hereinafter, a channel divider, a sound reproduction system including the same, and a method of setting a crossover frequency of the channel divider according to preferred embodiments of the present invention will be described, but the present invention is not limited to these embodiments.

  1 and 3 are diagrams 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 12 and speaker systems 7L and 7R connected to the amplifier device 1, and FIG. 1 and FIG. 3 are blocks showing their internal configurations. 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. FIG. It is a graph explaining the gain frequency characteristic and phase frequency characteristic of filter COM1 and 2nd comb filter COM2. FIG. 5 is a graph illustrating the output characteristics (first output signal D1 and second output signal D2) of the 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.

  The sound reproduction system includes an amplifier device 1 and speaker systems 7L and 7R connected to the amplifier device 1, converts digital signal data data input to the amplifier device 1 into stereo audio signals L and R, and the amplifier device. This is a sound reproduction system for reproducing stereo sound by a speaker system 7 composed of two speakers 7L and 7R after being amplified at 1. The amplifier device 1 includes a DSP and a multi-amplifier, and can be connected to a multi-amplifier that operates a channel divider. The speaker system 7 is a 2-way bi-wiring SS including a woofer WO and a tweeter TW, respectively, and is bi-wiring connected to the amplifier device 1 by a speaker cord. Therefore, the user who uses the amplifier device 1 can adjust the reproduction quality of the speaker system 7 by adjusting the channel divider to change the frequency band and the reproduction level in which the woofer and the tweeter overlap and reproduce. Become.

  The amplifier device 1 includes a DSP (digital signal processor) 10 that performs signal processing of digital signal data data, a D / A converter 2 that receives outputs from the DSP 10 for four channels, and converts them into analog signals, and these analog signals. And an amplifier circuit 3 for amplifying each of the signals and outputting them 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 that is a control circuit that controls the whole, an operation unit 5 that is connected to the CPU 4 and receives an instruction input from a user, and a display circuit 6 that includes a display. Specifically, the amplifier device 1 can be configured by a DSP that supports multi-channel sound, an AV receiver that incorporates 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 a display device connected to another. Of course, the amplifier device 1 may be constituted by another sound reproducing device including the DSP 10, the D / A converter 2, the multi-channel amplifier circuit 3, and the CPU 4 such as a microcomputer. Further, the DSP 10 included in the amplifier device 1 may be independent as a single channel divider device.

  The speaker system 7 is a 2-way bi-wiring SS including a woofer WO and a tweeter TW, and includes an input terminal corresponding to each speaker unit. The woofer WO for low sound region reproduction of the left speaker 7L and the right speaker 7R is connected to the input terminal tL, and the tweeter TW for high sound region reproduction is connected to the input terminal tH. Since the speaker system 7 is a speaker system that does not have a network circuit therein, the DSP 10 included in the amplifier device 1 constitutes a channel divider and band-divides the audio signal and outputs it to the input terminals tL and tH.

  FIG. 2A is a graph for explaining the sound pressure frequency characteristics of the speaker system 7. The reproduction frequency band of the woofer WO and the tweeter TW of the speaker system 7 of this embodiment is determined from various conditions such as the diaphragm area. In the case of the speaker system 7, since the frequency band for audio reproduction is not mainly divided by the network circuit, the reproduction sound of the speaker system 7 near the frequency fc shown in the figure is as shown in FIG. In addition, the reproduced sound from the woofer WO and the reproduced sound from the tweeter TW overlap widely. Therefore, the vicinity of the frequency fc where the woofer WO and the tweeter TW can reproduce at the same sound pressure level is suitable as the crossover frequency set by the channel divider. In this sound reproduction system, the woofer WO for low frequency reproduction mainly reproduces a frequency band below the crossover frequency fc set by the channel divider, and the tweeter TW mainly reproduces a frequency band above the crossover frequency fc. To do. In the case of a 2-way speaker system, the crossover frequency fc is generally set between about 1 to 8 kHz.

  The DSP 10 includes therein a decoder 11 that converts input data data into stereo signals L and R, and a channel divider 12 that includes a digital filter. The DSP 10 outputs the output terminals (DL1, DL2, DR1, DR2) for four channels of the channel divider 12 to the D / A converter 2. The channel divider 12 includes a low-pass filter LPF, a band-pass filter BPF, a high-pass filter HPF, a first comb filter COM1, and a second comb filter COM2 respectively corresponding to the left signal L and the right signal R. A first adder 15, a second adder 16, a first output adjustment circuit 17, and a second output adjustment circuit 18 are included. The CPU 4 controls the filter settings 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.

  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 FIR filters or IIR filters. The low-pass filter LPF, the band-pass filter BPF, and the high-pass filter HPF are preferably Butterworth filters, Linkwitz-Riley filters, and the like, and may include linear phase characteristics by FIR filters. As shown in FIG. 2B, the channel divider 12 divides the input audio signal into three frequency bands by a low-pass filter LPF, a band-pass filter BPF, and a high-pass filter HPF. As shown in FIG. 2, the channel divider 12 sets the cutoff frequencies of the three filters so that the crossover frequency fc between the woofer WO and the tweeter TW is included in the passband of the bandpass 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 set to the cutoff of the high pass filter HPF. Set equal to the frequency fh.

  In the channel divider 12 of the amplifier device 1 of the present embodiment, as shown in FIG. 3, the cutoff frequency fl of the low-pass filter LPF is set to 1.6 kHz, and the cutoff frequency of the high-pass filter HPF. fh is set to 4 kHz, and the pass band of the band pass filter BPF is set to 1.6 kHz to 4 kHz. In FIG. 3, 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.

  The first comb filter COM1 and the second comb filter COM2 to which the output of the band pass filter BPF is input are configured to output two signals that are out of phase with each other by 90 degrees and are uncorrelated with each other. Specifically, as shown in FIG. 3, the first comb filter COM1 and the second comb filter COM2 share the multiplier 13 to which the output of the bandpass filter BPF is input and the delay circuit 14 (Delay). Included. The multiplier 13 adjusts the level and multiplies the coefficient 0.5 so that the output of the bandpass filter BPF is reproduced when the two outputs of the first comb filter COM1 and the second comb filter COM2 are added. The delay circuit 14 delays the output signal of the branched multiplier 13 by a predetermined time and inputs the delayed signal to the adder 19 and the subtracter 20. The adder 19 adds the output of the multiplier 13 that is the output signal of the bandpass filter BPF and the output of the delay circuit 14 and outputs the result to the adder 15. On the other hand, the subtracter 20 subtracts the output of the delay circuit 14 from the output of the multiplier 13 that is the output signal of the bandpass filter BPF, and outputs the result to the adder 16. That is, the first comb filter COM1 and the second comb filter COM2 are configured to add or subtract the delayed input signal to the branched input signal.

  The first adder 15 adds the output of the low-pass filter LPF and the output of the adder 19 and inputs the result to the first output adjustment circuit 17, and outputs the first audio output signal D1 as the output terminal (DL1,. Output to DR1). Further, the second adder 16 adds the output of the low-pass filter LPF and the output of the adder 20 and inputs the result to the second output adjustment circuit 18, and outputs the second audio output signal D2 as the output terminal of the DSP 10 ( DL2, DR2). Note that the first output adjustment circuit 17 and the second output adjustment circuit 18 expand the range for adjusting the reproduction sound quality so as to be compatible with a wide range of speaker systems 7, and 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 the delay time.

  FIG. 4 is a graph illustrating gain frequency characteristics and phase frequency characteristics of the first comb filter COM1 and the second comb filter COM2. As shown in FIG. 4 (a), the output of the first comb filter COM1 is such that the lowest dip frequency that appears matches the cutoff frequency fh (= 4 kHz) of the high-pass filter HPF. The delay time set in is set. On the other hand, as shown in FIG. 4B, the lowest peak frequency that appears in the output of the second comb filter COM2 matches the cutoff frequency fh (= 4 kHz) of the high-pass filter HPF. Further, as can be seen from the graph of the phase characteristics, the output of the first comb filter COM1 and the output of the second comb filter COM2 always have a phase difference of 90 degrees relatively. Therefore, the output of the first comb filter COM1 and the output of the second comb filter COM2 have an uncorrelated relationship in which the output of the flat band-pass filter is reproduced even if they are added or subtracted. The output of the band pass filter BPF is input to the first comb filter COM1 and the second comb filter COM2. In this embodiment, the pass band of the band pass filter BPF is set to 1.6 kHz to 4 kHz, and the roll forms the lowest dip in the first comb filter COM1 and the lowest peak in the second comb filter COM2. Using the off characteristics, each band-divided signal is output.

  In normal audio reproduction, the channel divider 12 is provided with 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. Further, the output of the band-pass filter BPF is input to the first comb filter COM1 and the second comb filter COM2 so as to be uncorrelated with each other, and added to the output of the low-pass filter LPF or the high-pass filter HPF. That is, the crossover is performed by adding the output components of the band-pass filter BPF to 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 in an uncorrelated relationship with each other. The reproduction sound quality of the multi-way speaker system can be changed by relatively widening the overlap of the reproduction sounds from the woofer and the tweeter near the frequency.

  FIG. 5 is a graph for explaining the output characteristics of the channel divider 12 of the amplifier device 1 (FIG. 5 (a): second audio output signal D2, FIG. 5 (b): first audio output signal D1). The output characteristic of the first audio output signal D1 is that the output level of the low-pass filter LPF whose passband output level is 0 dB or less at the cutoff frequency fl and the output level of the passband is limited to the frequencies fl to fh. The output of the band-pass filter BPF having the roll-off of the dip characteristic of the one comb filter COM1 has a characteristic as shown in the figure, and the cutoff frequency fh or higher is the stop band. On the other hand, the output characteristics of the second audio output signal D2 are the output of the high-pass filter HPF having a passband output level of 0 dB or higher at the cutoff frequency fh and the output of the passband that is band-limited to the frequencies fl to fh. The level has a characteristic as shown in the figure obtained by adding the output of the band-pass filter BPF having the roll-off of the peak characteristic of the second comb filter COM2, and the cutoff frequency fl or less is the stop band.

  Thus, the predetermined frequency band component of the corresponding band pass filter BPF is included at a high gain level in each of the first sound output signal D1 on the low sound side and the second sound output signal D2 on the high sound band side. Thus, the superposed band of the first sound output signal D1 on the low sound range side and the second sound output signal D2 on the high sound range side can be set wider than intended by other filters. When the sound pressure level of the reproduced sound wave from the woofer WO and the reproduced sound wave from the tweeter TW becomes wider, the band in which the sound waves interfere in phase becomes wider, so the directional characteristics of the speaker system change and the reproduced sound quality is improved. Change. Further, in this channel divider 12, a flat 0 dB gain characteristic can be obtained by adding or subtracting 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 characteristics do not increase or decrease regardless of the phase characteristics of the woofer WO and the tweeter TW, and the low frequency range side The overlapping band between the LPF and the HPF on the high sound range side can be set wide.

  In the channel divider 12 as in the present embodiment, when the crossover frequency fc that can be set by the speaker system 7 is set so that the cutoff frequencies fl and fh are included in the passband of the bandpass filter BPF, a basic speaker The sound pressure frequency characteristic of the system 7 can be adjusted without changing, and the reproduction sound quality of the superimposition band of the sound reproduction system can be changed. For example, when stereo sound is played back in the 2-way speaker system 7, there is a playback band of the singer's vocal sound across the crossover frequency fc. Therefore, if the channel divider 12 sets a steep transition range characteristic, the woofer WO The sound image is such that the interference between the reproduced sound wave of the tweeter and the reproduced sound wave of the tweeter TW is substantially reduced, and the user can make the vocal size of the singer smaller than when the channel divider 12 is not functioned. A feeling can be obtained. On the other hand, if the interference between the reproduced sound wave of the woofer WO and the reproduced sound wave of the tweeter TW can be adjusted intentionally as in this embodiment, the user only has to change the filter configuration or the crossover frequency setting. It is possible to obtain a desired sound image feeling by adjusting the directivity characteristics of the speaker system 7. Of course, it is preferable that the cutoff frequencies 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, the JIS standard (or ISO / IEC standard) is used. It may be set in steps of about 1/3 octave or 1/6 octave. Further, it is preferable that the band of the band pass filter BPF can be freely set in a range of about 1/6 to 4 octaves.

  In the above embodiment, when the cutoff frequency fh of the high-pass filter HPF is set, the delay times of the delay circuits 14 of the first comb filter COM1 and the second comb filter COM2 are set in conjunction with each other. However, the first comb filter COM1 and the second comb filter COM2 of the channel divider 12 are not limited to those in the above embodiment. The delay time in the delay circuit 14 may be further increased so that a plurality of peaks and dips appear in the pass band of the band pass filter BPF, or no peaks and dips appear in the pass band of the band pass filter BPF. As described above, the delay time in the delay circuit 14 may be further shortened. If the output components of the band-pass filter BPF can be added to the first sound output signal D1 on the low sound range side and the second sound output signal D2 on the high sound range side in an uncorrelated relationship with each other, the first comb shape The configuration of the filter COM1 and the second comb filter COM2 and the setting of the delay time may be independent from the setting of the cutoff frequency of the band pass filter BPF.

  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. The channel divider 12 is a 3-5 way multi-way speaker including a subwoofer and / or a mid range and / or a super tweeter (not shown) to 3-5 for 3-5 way to accommodate bi-wiring SS. A configuration including an output obtained by dividing a band may be used. The band pass filter BPF may be configured by connecting another low pass filter HPF or another low pass filter LPF in series to the low pass filter LPF and the high pass filter HPF.

  Of course, the channel divider 12 of this embodiment is also effective in the case of a multi-way speaker including a woofer including a network circuit and a tweeter. Similarly, the channel divider 12 is effective when the speaker system 7 includes a full range speaker. Even when a substantial crossover frequency fc with other speakers is set in response to a decrease in level due to the limit of the reproduction sound pressure frequency characteristics of full range speakers or speakers such as woofers and tweeters, In accordance with this, the band pass filter BPF of the channel divider 12 can be set.

  FIG. 6 is a diagram illustrating another filter configuration of the channel divider 12 of the amplifier device 1 according to the 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 the previous embodiment. Since the filter configurations on the left signal L side and the right signal R side are the same, only one side is illustrated, and the description of the common part and the illustration and description of the other side are omitted.

  In the channel divider 12 of the amplifier device 1 of the present embodiment, the cut-off frequency fl of the low-pass filter LPF is set to 1.6 kHz, the cut-off 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. However, the band-pass filter BPF having a pass band of 1.6 kHz to 4 kHz is a low-pass filter with a cut-off frequency fl set to 1.6 kHz from the output of the low-pass filter LPF 1 with the cut-off frequency fl set to 4 kHz. The output of the pass-pass filter LPF is subtracted.

  Further, the high-pass filter HPF is configured to subtract the signal obtained by delaying the input audio signal by the delay circuit Delay and the output of the low-pass filter LPF1 having a cutoff frequency fl of 4 kHz. The delay time in the delay circuit Delay is set equal to the delay time of the FIR linear phase filter constituting the low-pass filter LPF1. By doing so, the filter configuration of the channel divider 12 can be simplified. When the low-pass filter LPF1 is composed of a non-linear phase IIR filter, the input audio signal and the output of the low-pass filter LPF1 may be subtracted without providing a delay circuit. Good. Note that the low-pass filter LPF may be configured to subtract the signal obtained by delaying the input audio signal by the delay circuit Delay and the output of another high-pass filter HPF.

  Further, the configuration including the first comb filter COM1 and the second comb filter COM2 of the channel divider 12 is not limited to the configuration described and illustrated in the above embodiment. In other words, the configurations of the first comb filter COM1 and the second comb filter COM2 are not limited to the feedforward type that adds or subtracts the delayed signal and outputs the delayed signal. The feedback type may be a cyclic type. That is, the output of the low-pass filter LPF and one of the outputs of the non-correlated band-pass filter BPF are added by the first adder 15 to form a first output signal, and the band that has been decorrelated with the high-pass filter HPF. The other output of the pass filter BPF may be added by the second adder 16 to form a second output signal, and a predetermined overlapping band may be provided. The user can easily change the playback sound quality of the multi-way speaker system by changing the overlap of the playback sound from the woofer and tweeter near the crossover frequency.

  The channel divider of the present invention can be applied not only to a stereo apparatus that reproduces a stereo audio signal, but also to an audio reproduction system including a multi-channel surround sound reproduction apparatus.

DESCRIPTION OF SYMBOLS 1 Amplifier apparatus 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

Claims (7)

The input audio signal is band-divided into at least a first output signal on the low sound region side and a second output signal on the high sound region side of the first output signal, and output to the first output terminal and the second output terminal, respectively. A channel divider,
A low-pass filter and a high-pass filter to which the input speech signal is input, respectively, a lower-limit cutoff frequency equal to a cutoff frequency of the low-pass filter that is input to the input speech signal, and the high-pass filter A bandpass filter that sets an upper limit cutoff frequency equal to the cutoff frequency, a first comb filter that receives an output of the bandpass filter, a second comb filter that receives an output of the bandpass filter, A first adder for adding the output of the low-pass filter and the output of the first comb filter; and a second adder for adding the output of the high-pass filter and the second comb filter;
The output of the first adder is the first output signal, and the output of the second adder is the second output signal.
Channel divider. The first comb filter and the second comb filter are configured to output mutually uncorrelated signals, and level adjustment is performed so that the output of the band-pass filter is reproduced when the outputs are added to each other. Including multiplier,
The channel divider according to claim 1. A delay circuit for branching and delaying the input output signal of the bandpass filter; and an adder for adding the output signal of the bandpass filter and the output signal of the delay circuit. Configured to include
The second comb filter is configured to include the delay circuit and a subtractor that subtracts the output signal of the delay circuit from the output signal of the bandpass filter.
The channel divider according to claim 1 or 2. The delay time set by the delay circuit is the lowest dip frequency that appears in the output characteristics of the first comb filter, or the lowest peak frequency that appears in the output characteristics of the second comb filter, and the high frequency band Set to match the cutoff frequency of the pass filter,
The channel divider according to claim 3. The band pass filter is configured to subtract the output of a low pass filter that passes two adjacent frequency bands in the pass band;
The high-pass filter is configured to subtract the input audio signal or a signal obtained by delaying the input audio signal and an output of a low-pass filter having the upper limit cutoff frequency as a cutoff frequency.
The channel divider according to any one of claims 1 to 4. A level adjustment circuit for adjusting a level of the first output signal or the second output signal; a phase inversion circuit for performing phase inversion of the first output signal or the second output signal; and the first output signal or the second output signal. A delay circuit for adjusting a delay time of the two output signals;
The channel divider according to any one of claims 1 to 5. A speaker comprising at least a channel divider according to any one of claims 1 to 6, an amplifier including an amplifier circuit corresponding to each output terminal of the channel divider, and a woofer and a tweeter and capable of bi-wiring connection with the amplifier. And a sound reproduction system including the system.

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