JPS63300700A - Time difference correcting device for audio system - Google Patents

Abstract

PURPOSE:To prevent an arrival difference in sound by providing plural delay circuits for each split frequency band and adjusting the delay time of each delay circuit in response to the arrangement of speakers thereby allowing sound waves from the speakers to arrive at a listener at the same time. CONSTITUTION:An inputted digital audio signal is inputted in parallel with filters 51, 52, 53 consisting of band split circuits and split into frequency bands by the characteristic of each filter. The signal subjected to band split is given to digital delay circuits DLY 61, 62, 63, and retarded by a delay time decided by the signal from a control block 7 and sent to a digital synthesis circuit MIX 8. the MIX 8 combines the signal inputted in parallel into one channel signal and sends it to the next stage. A D/A converter DAC 5 converts the input into an analog signal to eliminate excess frequency components caused by the conversion at the LPF 6, the result is amplified by a power amplifier P, AMP3 and outputted to a speaker system 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a time difference correction device in an audio system, particularly in an audio system for multi-speakers.

[Summary of the invention]

This invention provides an audio system that includes speakers with different characteristics depending on the frequency band of the audio signal, in which the audio signal is divided into a plurality of frequency bands depending on the characteristics of each speaker, and a delay circuit is provided for each frequency band. ,
By adjusting the delay time of each delay circuit according to the placement of each speaker, the difference in arrival time of sound waves from each speaker to the listener is corrected, and disturbances in frequency characteristics due to sound misalignment and interference between each speaker are prevented. It was made so that it could be done.

[Conventional technology]

Generally, the reproducible sound range of a single speaker is narrower than the human audible range (20 Hz to 20 KHz).

A large diaphragm is necessary to efficiently reproduce low-frequency sounds (hereinafter referred to as "bass sounds"), but when high-frequency sounds (hereinafter referred to as "treble sounds") are reproduced with such a diaphragm, the piston movement becomes unstable. When it becomes stable, split vibrations occur, and the sounds interfere with each other, making the frequency characteristics irregular and not flat.

Furthermore, even if the frequency characteristics are flat, if high and low tones are reproduced simultaneously, it is impossible to avoid Doppler distortion (a type of cross-modulation distortion) in which the high tones are modulated by the low tones and the sound becomes muddy.

Conventionally, a multi-speaker system has been proposed as a way to solve these drawbacks and obtain wide and flat frequency characteristics with little distortion, in which multiple speakers each having different frequency characteristics share the playback according to the frequency band of the audio signal. there were.

For example, as shown in FIG. 5, a power amplifier (P.

A dividing circuit (DN) 40 that divides the output from the AMP)'3 into a bass range, a midrange range, and a treble range, and a large-diameter speaker (hereinafter referred to as "
41 (also referred to as "woofer"), a medium-diameter speaker (hereinafter also referred to as "squawka j") 42 that reproduces midrange, and a small-diameter speaker (hereinafter also referred to as "tweeter") 43 that reproduces high-frequency range. way speaker system (
SP system) 4 is available.

FIG. 6 is an explanatory diagram showing an example of the frequency characteristics of the signal divided into each band by the dividing circuit 40, where , M, and H are characteristic curves of the bass range, middle range, and treble range, respectively. In this figure, the intersection point P1. of adjacent characteristic curves. P2 is a crossover point, and the frequency f′′2 corresponding to each intersection is a crossover frequency.

[Problem that the invention seeks to solve]

In such a multi-speaker system, as shown in FIG. 7, the sound source centers 41c, 42c, and 43c of the three speakers 41, 42, and 43 are at the same distance from the listener 45, that is, in the same circular arc centered on the listener 45. When they are on the same spherical surface, the sound waves Su and S from each speaker
Since s and St reach the listener 45 at the same time, there is no problem.

However, generally, as shown in FIG. 8, these speakers 41, 42, 4; are often attached to a single baffle plate 46 or the front plate of the same speaker box. In this case, the sound source centers 41c, 42c of the speakers 41, 42, 43.

Since 43c is not equidistant from the listener 45, the sound waves Su,
The arrival times of Ss and St to the listener 45 are shifted.

In addition, in a speaker system using a horn speaker as shown in FIG. 9, the woofer 41h, squawker 42h, and tweeter 43h generally have significantly different horn lengths, so the sound waves Su, Ss, and St from each speaker are In many cases, the difference in arrival time to the listener 45 becomes large.

If there is a difference in arrival time in this way, a sound shift or a sound phase shift occurs, especially at the crossover point P1 shown in FIG. P
2, the difference in arrival time is the crossover frequency f□
When the frequency becomes approximately an odd multiple of the half period of rfz, interference of sound waves occurs, causing a valley in the frequency characteristics of the synthesized sound, as shown by the broken line in FIG.

Particularly in the case of stereo playback, there is a problem in that if there is such a sound shift or valley in the frequency characteristics in the midrange, the localization of the sound source will be greatly affected.

This invention aims to solve these problems.

[Means for solving problems]

In order to solve the above problems in an audio system for multi-speakers as described above, the present invention provides a band division circuit that divides an audio signal into a plurality of frequency bands according to the characteristics of each speaker, and a band division circuit that divides an audio signal into a plurality of frequency bands according to the characteristics of each speaker. This system includes a plurality of delay circuits that delay audio signals for each divided frequency band, and a delay time adjustment means for adjusting the delay time of each delay circuit according to the arrangement of each speaker.

[For production]

By inserting this time difference correction circuit into the audio signal processing system of the audio system described above and adjusting the delay time of each delay circuit according to the arrangement of each speaker, the sound waves from each speaker reach the listener at the same time. As a result, sound deviation and sound interference can be eliminated.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 to 3 are block diagrams of embodiments in which the time difference correction device according to the present invention is provided in the signal processing circuit of a digital audio system, and FIG. 4 in the signal processing circuit of an analog audio system, respectively. 1 is an input terminal for audio signals, and 2 is an output terminal.

In the first embodiment shown in FIG. 1, the input digital audio signal is filtered through a digital low-pass filter (hereinafter also referred to as "digital LPFJ") constituting a band division circuit.
51. Digital bandpass filter (hereinafter referred to as “Digital B”)
The signals are input in parallel to a 52° digital bypass filter (hereinafter also referred to as "digital HPFJ") 53, and are divided into frequency bands according to the characteristics of each filter.

The three-channel digital audio signal band-divided by each of these filters is sent to each digital delay circuit (DLY) 61, 82 . E); and is delayed by a delay time determined by the signal from the control block (CONT BLK) 7 and sent to the digital synthesis circuit (MIX) 8.

The digital synthesis circuit 8 synthesizes the three channel signals input in parallel again into a one channel digital audio signal, and outputs the signal from the output terminal 2 to the next stage.

The digital audio signal output from output terminal 2 is
After being converted into an analog audio signal by a digital-to-analog converter (DAC) 5, it passes through a low-pass filter (LPF) 6 to remove extra frequency components generated by the conversion, and is amplified by a power amplifier 3 and sent to a speaker system 4. Output.

The control block 7 includes each of the digital filters 51 and 52 described above.
．． 53 frequency bands and each digital delay circuit 81, 62
．． It is a circuit block that outputs a digital signal indicating the delay time of 63, and has the function of delay time adjustment means,
These digital signals are determined by the set values of variable resistors VRI to VR5.

Variable resistors VRI, VR2, and VR3 are each connected to a digital delay circuit E31. This is to adjust the delay time of E32 and E83. The variable resistor VR4 controls the low frequency side of the digital BPF52 and the cutoff frequency of the digital LPF51.
5 is the high frequency side of digital BPF52 and digital HPF5;
Determine the cutoff frequency of each.

The switch (sw) 71 and the gate (GATE) 72 operate synchronously with the clock from the switch controller (SW CONT) 73, and each digital filter 51 to
53 and digital delay circuits 61-63.

When the switch 71 selects one of the variable resistors VRI to VR5, the set value (analog) is digitized by an analog-to-digital converter (ADC) 74 and sent to an address recorder (ADR, REC) 75. The address recorder 75 reads code information according to the digital signal input from the memory (ROM) 7B,
The signal is sent through the gate 72 to the circuit corresponding to the variable resistor selected by the switch 71.

In this way, the delay time of each channel can be adjusted by the variable resistors VRI to VR3 according to the arrangement of the speakers sharing each band, and the difference in arrival time of sound waves can be set to O. Variable resistance VRI.

VH2 is provided to match each speaker and each delay circuit by matching the passbands of digital filters 51 to 53 to the assigned bands of each speaker.

The delay time of each channel is relative, and the delay time of the channel corresponding to the farthest speaker can be set to O. If the speaker whose center is the farthest apart is known in advance, the delay circuit for the channel corresponding to that speaker can be omitted.

The same applies to the following examples.

The second embodiment shown in FIG. 2 is the same as the first embodiment shown in FIG. 1 except that an amplifier system dedicated to the woofer 41 is provided separately, and the same parts are given the same reference numerals and explanations will be omitted. .

Among the three channels of digital audio signals delayed by the digital delay circuits 61 to 6B, the low-frequency digital audio signal output from the digital delay circuit 61 is sent from the output terminal 2a to the digital-to-analog converter 5a and the low-pass filter. 6a and a power amplifier 3a to drive a woofer 41.

The other two channels, namely the digital delay circuit 82.6
The mid-range and high-range digital audio signals delayed by 3 are synthesized into a 1-channel digital audio signal by the digital synthesis circuit 8, and then output to the output terminal 2b.
The signal passes through a digital-to-analog converter 5b, a low-pass filter 6b, and a power amplifier 3b to drive the squawker and tweeter of the speaker system 4.

Similarly, the amplifier system for tweeters is a woofer.

Even if it is provided separately from the amplifier system that also serves as the squawker, the present invention can be implemented in the same way.

The third embodiment shown in FIG. 3 is different from the second embodiment shown in FIG. 2 in that a dedicated amplifier system is provided for each of the squawker 42 and the tweeter 43 = 11-. are given the same reference numerals.

In this case, a digital synthesis circuit is no longer necessary, and the band-divided three-channel digital audio signals are delayed by digital delay circuits 61, 62 and 63, respectively, and then passed through respective output terminals 2a, 2b, and 2c. ,
Digital-to-analog converters 5a, 5b, 5c, low-pass filter F3 a +5b, 5c, and power amplifier 3
a, 5b, and 3c, each of which is amplified by a dedicated amplifier system, and woofers 41. Skouka 42. Towita 4
3, respectively.

In this way, even if each speaker is connected to an independent dedicated amplifier system, it is still a multi-speaker system.

The fourth embodiment shown in FIG. 4 is an example in which a signal from an analog audio source or a digital audio signal is converted into an analog signal by a digital-to-analog converter and a low-pass filter, and then time difference correction is performed.

An analog audio signal input from the input terminal 1 passes through a buffer amplifier (BUF AMP) 9 and is then divided into three channels by frequency band by filters 55 to 57.

The low frequency signal that has passed through the low pass filter 55, the mid frequency signal that has passed through the band pass filter 56, and the high frequency signal that has passed through the bypass filter 57 are each processed by changing the delay time of an analog delay element such as a BBD element. Analog delay circuit (ADLY) 65.86.
After being delayed by 87, the analog synthesis circuit (AMIX
)10.

After being synthesized again into a single-channel analog audio signal by this analog synthesis circuit 10, the signal is inputted from the output terminal 2 to the power amplifier 3, where it is amplified and drives the speakers for each band of the speaker system 4.

Variable resistors VRI, VR2, and VR3 are used to adjust the delay time of analog delay circuits 85, 86, and 87, respectively.

Further, VR4' is the cutoff frequency of the low-pass filter 55 and the low-frequency side of the band-pass filter 56, and VR5' is the high-frequency side of the band-pass filter 56 and the bypass filter 57.
The interlocking variable resistors are used to adjust the cutoff frequency of each speaker in conjunction with each other in accordance with the characteristics of each speaker, but depending on the design, it may be possible to adjust the cutoff frequency of each speaker independently.

Even in such an analog audio system, a dedicated amplifier system may be provided for each frequency band, as in the example of the digital audio system shown in FIGS. Of course, it is possible to apply

Above, an example of a 3-way speaker system consisting of a woofer, a squawker, and a tweeter has been described, but a 2-way speaker system consisting of a woofer and a tweeter, or a 4-way speaker system in which a super woofer for heavy bass is added to a 3-way speaker system has been described. Even in the case of a way speaker system, etc., it is sufficient to increase or decrease the filter for band division, the delay circuit, and the variable resistor for adjusting the delay time.

〔Effect of the invention〕

As described above, by using the time difference correction device according to the present invention, it is possible to eliminate the difference in arrival time of sound waves due to the arrangement of each speaker in a multi-speaker audio system.

[Brief explanation of the drawing]

1 to 3 are block diagrams showing first to third embodiments in which the present invention is applied to a digital audio system, respectively. FIG. 4 shows a fourth embodiment in which the present invention is applied to an analog audio system. Block diagram, Fig. 5 is a block diagram showing an example of a multi-speaker system, Fig. 6 is an explanatory diagram showing an example of the playback range of each speaker and the overall sound field level in a 3-way speaker system, Figs. 7 to 9 These are model diagrams showing different examples of the arrangement of each speaker of a 3-way speaker system and the progress state of the sound waves. 1...Input terminals 2.2a, 2b, 2c"' Output terminals 3.5a, 3b, 3c"'Power amplifier 4...Speaker system 41...Woofer 42...Squawker 43...
Tweeter 5.5a, 5b, 5c...Digital-to-analog converter 6.8a, 6b, 5c...Low pass filter 7...
Control block (delay time adjustment means) 8...Digital synthesis circuit 9...Buffer amplifier 10...Analog synthesis circuits 51 to 53/Digital filter (band division circuit) 61
~63...Digital delay circuit 55-57...Analog filter (band division circuit) 6
5-67...Analog delay circuit VRI-VR5...Variable resistor Fig. 5 Fig. 7 Fig. 6 f1f2 - Frequency Fig. 8

Claims (1)

[Claims] 1. A band division circuit that divides an audio signal into a plurality of frequency bands according to the characteristics of each speaker in an audio system including a plurality of speakers having different frequency characteristics depending on the frequency band of an audio signal. , a plurality of delay circuits that delay audio signals for each frequency band divided by the band division circuit, and a delay time for adjusting the delay time of each delay circuit according to the arrangement of each of the speakers. 1. A time difference correction device comprising: adjustment means.