JP6015146B2 - Channel divider and audio playback system including the same - Google Patents

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 cutoff frequency of the off-frequency and the high-pass filter, a first multiplier and a second multiplier that output by changing the output level of the band-pass filter, and a low A first adder for adding the output of the pass filter and the output of the first multiplier, and an output of the high pass filter and the output of the second multiplier are added. 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.

  Preferably, the channel divider of the present invention includes a plurality of n bandpass filters in which the bandpass filter is divided into a plurality of frequency bands adjacent to each other, and the first multiplier and the second multiplier are a plurality of n. The first adder adds the output of the low-pass filter and the outputs of the plurality of n first multipliers, and the second adder provides the output of the high-pass filter. The output and the output of the second multiplier of n are added.

  Preferably, in the channel divider of the present invention, when the first multiplier multiplies the coefficient α (0 ≦ α ≦ 1), the second multiplier multiplies the coefficient (1-α).

  Preferably, the channel divider according to the present invention is configured such that when the coefficient α is 0.5, the predetermined bandpass filter corresponding to each of the first output signal on the low frequency side and the second output signal on the high frequency range is provided. Frequency band components are equally included.

  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 LPF and a high-pass filter HPF to which an input audio signal is respectively input, and a lower limit cutoff frequency equal to the cutoff frequency of the low-pass filter LPF to which an input audio signal is input. A band-pass filter BPF that sets an upper limit cutoff frequency equal to the cutoff frequency of the high-pass filter HPF, a first multiplier and a second multiplier that output by changing the output level 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, The output of one adder is a first output signal, and the output of the second adder is a 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 low pass filter LPF and the output of the band pass filter BPF are added by the first adder to form a first output signal, and the outputs of the high pass filter HPF and the band pass filter BPF are added to the second adder. To obtain the second output signal. Therefore, the channel divider according to the present invention adjusts the coefficients to be multiplied by the first multiplier and the second multiplier for the first output signal on the low frequency range side and the second output signal on the high frequency range side, respectively. The output component of the filter BPF can be added, and the reproduction sound from the woofer and tweeter near the crossover frequency can be adjusted relatively freely to change the reproduction sound quality of the multi-way speaker system. Can do.

  The channel divider of the present invention preferably causes the second multiplier to multiply the coefficient (1-α) when the first multiplier multiplies the coefficient α (0 ≦ α ≦ 1). By simply 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. Whether to reproduce (α = 0) or to reproduce from the woofer and the tweeter to the same extent (α = 0.5) can be changed by switching substantially steplessly. Further, when 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 low sound range side and the second output signal on the high sound range side. It will be. Therefore, since the minimum condition of flattening the addition characteristics of the LPF on the low frequency range and the HPF on the high frequency range is satisfied, the overlap of the reproduced sound from the woofer and tweeter near the crossover frequency is set appropriately. Thus, the playback sound quality of the multi-way speaker system can be changed. 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.

  Further, the band pass filter BPF may be composed of a plurality of n band pass filters that divide the frequency band into a plurality of adjacent frequency bands. In this case, a first multiplier and a second multiplier are provided at each of the outputs of the plurality of n bandpass filters, and a first adder outputs the output of the lowpass filter and the plurality of n first multiplications. And the second adder adds the output of the high-pass filter and the outputs 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, the level is adjusted for each band divided and reproduced from the woofer (α = 1) or reproduced from the tweeter (α = 0), or whether playback from the woofer and the tweeter to the same extent (α = 0.5) can be made. When a plurality of n band-pass filters BPF1 to BPFn are prepared at intervals of about 1/6 to 1/3 octave, the level of the band to be superimposed can be changed by combining and changing the coefficient α in each multiplier. In addition, the bandwidth of the overlapping band can be switched and set by changing only the coefficient α. 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 4 is a graph for explaining output characteristics (first output signal D1 and second output signal D2 (when α = 0.5)) of the channel divider 12 of the amplifier device 1; Example 1 4 is a graph for explaining output characteristics (first output signal D1 and second output signal D2 (when α = 1.0)) of the channel divider 12 of the amplifier device 1; Example 1 4 is a graph for explaining output characteristics (first output signal D1 and second output signal D2 (when α = 0)) 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) 6 is a table for explaining an example of combinations of gain coefficients a1 to a4 in the channel divider 12 of the amplifier device 1. (Example 2) 6 is a graph for explaining an example of output characteristics of the channel divider 12 of the amplifier device 1 (first output signal D1 and second output signal D2 (in the case of a superposition band of 2 to 4 kHz)). (Example 2) 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 3)

  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.

  FIG. 1 is a diagram illustrating 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 the internal configuration of each. 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, and FIGS. 4 is a graph for explaining output characteristics (first output signal D1 and 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.

  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 multiplier 13 and a second multiplier 14 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.

  The first multiplier 13 and the second multiplier 14 change the output level of the bandpass filter BPF and output the result. The first multiplier 13 multiplies the output of the bandpass filter BPF by a 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 a 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 the result to the first output adjustment circuit 17 to obtain the 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 sum to the second output adjustment circuit 18. The audio output signal D2 is output to the output terminals (DL2, DR2) of the DSP 10. 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.

  For 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. Then, it is adjusted how much the output of the band pass filter BPF is added to the output of the low pass filter LPF or the high pass filter HPF. That is, by adjusting and adding a single coefficient α to the output component of the bandpass filter BPF to each 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, 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.

  FIG. 3 shows output characteristics of the channel divider 12 of the amplifier device 1 (FIG. 3A: second audio output signal D2, FIG. 3B: when the coefficient α of the first multiplier 13 is 0.5. It is a graph explaining 1st audio | voice output signal D1). The output characteristics of the first audio output signal D1 are that the output level of the low-pass filter LPF whose passband output level is 0 dB or less below the cut-off frequency fl and the output level of the passband that is band-limited to the frequencies fl to fh are − The output of the 6 dB bandpass filter BPF is added to the staircase 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 more above the cutoff frequency fh, and the output of the passband that is band-limited to the frequencies fl to fh. The output of the bandpass filter BPF having a level of −6 dB and a step characteristic as shown in the figure are added, and the cutoff frequency fl or lower is the stop band.

  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 sound output signal D1 on the low sound side and the second sound output signal D2 on the high sound side is obtained. The band components are included equally, and the superimposition band of the first audio output signal D1 on the low frequency side and the second audio output signal D2 on the high frequency side is set wider than intended by other conventional filters. be able to. 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, when the first audio output signal D1 on the low sound side and the second sound output signal D2 on the high sound side are added, a flat 0 dB gain characteristic is obtained. Therefore, in the vicinity of the crossover frequency fc of the speaker system 7, the gain characteristic does not increase or decrease, and the overlapping band of the low-frequency side LPF and the high-frequency side HPF can be flexibly adjusted. .

  FIG. 4 shows the output characteristics of the channel divider 12 of the amplifier device 1 when the coefficient α of the first multiplier 13 is 1.0 (FIG. 4A: second audio output signal D2, FIG. 4B: It is a graph explaining 1st audio | voice output signal D1). The output characteristic of the first audio output signal D1 is that the output of the low-pass filter LPF whose pass band output level is equal to or lower than the cut-off frequency fl is 0 dB, and the output level of the pass band is 0 dB limited to the frequencies fl to fh. The output of the band pass filter BPF is added to the output of the bandpass filter BPF, and the cutoff frequency fh or higher is the stop band. On the other hand, the output characteristic of the second audio output signal D2 has a characteristic as shown only in the output of the high-pass filter HPF whose output level in the pass band equal to or higher than the cut-off frequency fh is 0 dB, and has a cut-off frequency fh. The following is the stopping zone.

  5 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 (FIG. 5A: second audio output signal D2, FIG. 5B: It is a graph explaining 1st audio | voice output signal D1). The output characteristic of the first audio output signal D1 has a characteristic as shown only in the output of the low-pass filter LPF whose output level in the pass band below the cutoff frequency fl is 0 dB, and the cutoff frequency fl or higher is blocked. It is an area. 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 more above the cutoff frequency fh, and the output of the passband that is band-limited to the frequencies fl to fh. The output of the band-pass filter BPF having a level of 0 dB is added to the characteristics shown in the figure, and the cutoff frequency fl or less is the stop band.

  As described above, when the coefficient α is 1.0 or 0, the predetermined frequency band component of the band pass filter BPF includes only the first sound output signal D1 on the low sound side or the second sound on the high sound side. Only the output signal D2 is included. The coefficient α is set by the CPU 4 by controlling the DSP 10, and when the coefficient α is changed within the range of 0 to 1, the low-frequency range first audio output signal D1 and the high-frequency range second audio output signal D2 are: The superimposition band corresponding to the crossover frequency band of the speaker system 7 can be set to be more or equal to or less distributed to either the woofer WO or the tweeter TW, or can be adjusted with intention. In the channel divider 12, when 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 are added, a flat 0 dB gain characteristic is obtained. Therefore, when the user operates the operation unit 5 while looking at the display circuit 6 including the display, the CPU 4 controls the DSP 10 to change the coefficient α in the range of 0 to 1, so that the substantial crossover of the speaker system 7 is achieved. The frequency fc can be changed between the frequencies fl to fh.

  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 intentionally adjusted as in this embodiment, the user can change the orientation of the speaker system 7 only by changing the coefficient α. It is possible to obtain a desired sound image feeling by adjusting the characteristics. 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.

  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. FIG. 7 is a table for explaining examples of combinations of gain coefficients a1 to a4 in the channel divider 12. Further, FIG. 8 is a graph for explaining an example of output characteristics of the channel divider 12 of the amplifier device 1 (first output signal D1 and second output signal D2 (in the case of the superposed band 2k to 4 kHz)). 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 illustration and description on 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. Therefore, the user can set the crossover frequency fc of the speaker system 7 that is the bi-wiring SS in the range of 1.6 kHz to 4 kHz. Further, the band pass filter BPF is 1/3 Oct. It is composed of four band pass filters BPF1 to BPF4 that divide the frequency band into four frequency bands adjacent to each other at (octave) intervals. BPF1 uses 1.6k to 2kHz, BPF2 uses 2k to 2.5kHz, BPF3 uses 2.5k to 3.2kHz, and BPF4 uses 3.2k to 4kHz.

  A first multiplier 13 and a second multiplier 14 are provided at the outputs of the bandpass filters BPF1 to BPF4, respectively. The coefficients a1 to a4 in these first multipliers 13 are numerical values of 0 or more and 1 or less, and can be changed independently of each other. The second multiplier 14 is a numerical value obtained by subtracting the coefficients a1 to a4 in the corresponding first multiplier 13 from 1. Further, the first adder 15 adds the outputs of the low-pass filter LPF and the outputs of the four first multipliers 13. The second adder 16 adds the outputs of the high-pass filter HPF and the outputs of the four second multipliers 14. The first output adjustment circuit 17 and the second output adjustment circuit 18 each include 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.

  As shown in FIG. 7 and FIG. 8, in the channel divider 12 of the present embodiment, the band pass filter BPF is composed of four band pass filters BPF1 to BPF4, and the level is adjusted for each band divided into woofers. Playback from WO (coefficients a1 to a4 = 1), playback from tweeter TW (coefficients a1 to a4 = 0), playback from woofer WO and tweeter TW to the same extent (coefficients a1 to a4 = 0.5) Or you can change the balance and play from both. For example, when the combination of the coefficients a1 to a4 of the first multiplier 13 as shown in the table of FIG. 7A is used, the cut-off 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 a superposition band. 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 a superposition band.

  Next, when a combination of the coefficients a1 to a4 of the first multiplier 13 as shown in the table of FIG. 7B is used, a 1/3 octave can be provided for the 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 bandpass filters BPF1 to BPF4 is set to the superposition band, the coefficients a1 to a4 of the corresponding first multiplier 13 are set to 0.5, The coefficient of the other first multiplier 13 may be set to 1 or 0. Further, when the combination of the coefficients a1 to a4 of the first multiplier 13 as shown in the table of FIG. 7C is used, the superposed band reproduced from both the woofer WO and the tweeter TW is set to 1 octave (= 1/3 Oct. × (3 bands) can be provided. For example, as described in the left column of the table of FIG. 7C, the coefficient a4 of the first multiplier 13 of the bandpass filter BPF4 is set to 0, and the coefficients a1 to a3 of the other first multipliers 13 are set to 0. When set to .5, the first output signal D1 and the second output signal D2 can include the band components of the superposed band 1.6 k to 3.2 kHz equally.

  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 bandpass filter BPF1 is set to 1, and the coefficients a2 and a4 of the other first multipliers 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 first output signal D1 and the second output signal D2 are overlapped with each other. It is possible to satisfy the condition that the balance between 1.6 k and 3.2 kHz is intentionally changed and the addition characteristic is flat. 7 and 8 are merely examples, and the user who uses the channel divider 12 can easily overlap the reproduced sounds from the woofer WO and the tweeter TW near the crossover frequency fc. The reproduction sound quality of the speaker system 7 can be changed by changing the combination of the coefficients of the multiplier 13. In the above embodiment, the band pass filter BPF is divided into four bands. However, when the frequency band is widened or the width of the band to be divided is narrowed, it may be divided into 3 to 12 bands.

  In this embodiment, not only the level of the band to be superimposed by the channel divider 12 but also the bandwidth of the band to be superimposed can be switched and set by changing only the coefficient α. That is, if the characteristics of band division are changed by combining the coefficients a1 to a4 in the first multipliers 13, the filter characteristics of the low-pass filter LPF, the band-pass filter BPF, and the high-pass filter HPF. This eliminates the need to mute the output sound every time the filter characteristics are changed, and has the advantage that the audition can be confirmed in real time. Therefore, the user operates the channel divider 12 to check the synthesized sound of the sound reproduced from the woofer WO of the speaker system 7 and the sound reproduced from the tweeter TW, while changing the substantial crossover frequency fc. The sound quality can be finely adjusted.

  FIG. 9 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. Therefore, description of common parts is omitted.

  In the channel divider 12 of the present embodiment, the band pass filter BPF is common to the previous embodiment in that it 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 low in the cutoff frequency fl being set to 1.6 kHz from the output of the lowpass filter LPF1 having the cutoff frequency fl being set to 2 kHz. The output of the pass-pass filter LPF is subtracted. Similarly, the band-pass filter BPF2 having a passband of 2 kHz to 2.5 kHz has the cutoff frequency fl set to 2 kHz from the output of the low-pass filter LPF2 whose cutoff frequency fl is set to 2.5 kHz. The output of the low-pass filter LPF1 is subtracted.

  Similarly, the bandpass filter BPF3 having a passband of 2.5 kHz to 3.2 kHz has a cutoff frequency fl of 2.5 kHz from the output of the lowpass filter LPF3 in which the cutoff frequency fl is set to 3.2 kHz. The output of the low-pass filter LPF2 set to is subtracted. Similarly, in the band pass filter BPF4 having a pass band of 3.2 kHz to 4 kHz, the cutoff frequency fl is set to 3.2 kHz from the output of the low pass filter LPF4 in which the cutoff frequency fl is set to 4 kHz. The output of the low-pass filter LPF3 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 LPF 4 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 LPF4. By doing so, the filter configuration of the channel divider 12 can be simplified. When the low-pass filter LPF4 is configured by a non-linear phase IIR filter, the input audio signal and the output of the low-pass filter LPF4 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 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 that is multiplied by the second multiplier 14 with respect to the coefficient α that is multiplied by the first multiplier 13 is not limited to (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 be a first output signal, and the output of the high-pass filter HPF and the band-pass filter BPF are second-added. What is necessary is just to add together the predetermined | prescribed superimposition zone | band by adding in the device 16 as a 2nd 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 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 (6)

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 multiplier that multiplies the output of the bandpass filter by a coefficient α (0 ≦ α ≦ 1), and an output of the bandpass filter A second multiplier that multiplies the output by a coefficient (1-α), a first adder that adds the output of the low-pass filter and the output of the first multiplier, the output of the high-pass filter, and A second adder for adding the outputs of the second multiplier,
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 bandpass filter is composed of a plurality of n bandpass filters that divide a band into a plurality of adjacent frequency bands;
The first multiplier and the second multiplier are provided at the outputs of the plurality of n band-pass filters, respectively, and the first adder outputs the output of the low-pass filter and the plurality of n first filters. Adding the outputs of the multipliers, and the second adder adds the outputs of the high-pass filter and the outputs of the plurality n of the second multipliers,
The channel divider according to claim 1. When the coefficient α is 0.5, the first output signal on the low frequency side and the second output signal on the high frequency side equally include the predetermined frequency band component of the corresponding bandpass filter. ,
The channel divider according to claim 1 or 2 . 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 3 . 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 4 . A channel divider according to any one of claims 1 to 5, each of the amplifier including an amplifier circuit corresponding to the output terminal, woofer and at least includes the amplifier and the bi-wiring connection can speaker and tweeter of the channel divider And a sound reproduction system including the system.

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