JPH0449320B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a stereo playback device, and more particularly to a stereo playback device that can provide a sufficient stereo feeling even at a position away from the midpoint between left and right speakers that play back stereo signals.

In the case of a stereo reproduction device, a good stereo effect can be obtained at an intermediate position between the left and right speakers (a position on the bisector of the left and right speakers), but a sufficient stereo effect cannot be obtained outside this position.
Especially for car stereos, the location of the listener (driver's seat,
(passenger seat), it may not be possible to position it between the left and right speakers, making it impossible to obtain a sufficient stereo feeling.

For this purpose, for example, as shown in FIG. 1, a plurality of speakers 3 are arranged between the left and right speakers 1 and 2, and left and right stereo signals are distributed and supplied to these speakers 3 by an impedance element 4. A stereo playback device configured as follows has been proposed.

However, in the above-mentioned stereo playback device, unless the installation interval between speakers 1, 2, 3, etc. is widened, the sense of spaciousness of the sound will decrease due to the volume from the middle speaker 3, which is similar to a car stereo, etc. This is not suitable for use as a stereo playback device that is used in small spaces. In addition, when implementing the stereo playback device with the above configuration using three speakers, the stereo feeling at a position closer to either one of the left and right speakers 1 and 2 (hereinafter referred to as an offset position) is In order to improve this, if the volume of the speaker 3 located at the center is increased, the sound image that should be localized at the center will be moved slightly closer to the center, but the sense of spaciousness will deteriorate.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a stereo playback device that provides a sufficient stereo sound without deteriorating the sense of spaciousness even when the left and right speakers are offset from each other. .

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a block diagram showing an example of the stereo reproduction apparatus of the present invention. Reference numerals 5 and 6 in the figure indicate all-pass filters that have flat amplitude-frequency characteristics over the entire signal band, larger phase delays for lower frequency components, and smaller phase delays for higher frequency components. A phase shifter, 7 and 8 are power amplifiers, and 9 and 10 are left and right speakers.

The phase shifter 5 gives the left channel signal L a larger phase delay for lower frequency components, and the left channel signal L given such a frequency-dependent phase delay is supplied to the left speaker 9 by the power amplifier 7. . The phase shifter 6 gives the right channel signal R a larger phase delay for lower frequency components, and the right channel signal R given such a frequency-dependent phase delay is supplied to the left speaker 10 by the power amplifier 8. .

Further, 11 is an adder, 12 is an attenuator, 13 is a power amplifier, and 14 is a center speaker.

The adder 11 adds the right channel signal R and the left channel signal L in the same phase before being subjected to the frequency-dependent phase delay by the phase shifters 5 and 6 described above. These added left and right channel signals L and R
is attenuated by a predetermined attenuation amount At by the attenuator 12, and then transmitted to the left and right speakers 9, via the power amplifier 13.
The signal is supplied to a center speaker 14 located between the speakers 10 and 10.

FIG. 3 shows the phase shifters 5 and 6 that can be used in the present invention.
This is a circuit diagram showing an example of a phase shift circuit 1 in which the amplitude frequency characteristic is flat and the phase frequency characteristic is delayed from 0 to π.
5 are connected vertically in the required number. This phase shift circuit 15 is composed of an operational amplifier 16, a resistor R, and a capacitor C. Frequency ₀ at which the phase delay is π/2 is expressed by the following equation.

₀ = 1/2πRC _{The 0} of the phase shift circuit 15 of each stage is set to an appropriate frequency (for example, in the case of 10 stages, from 100 Hz to 1 KHz every 100 Hz) to obtain the necessary phase delay characteristic. Note that ₀ may be the same.

Next, the operation of the embodiment shown in FIG. 3 will be explained.

The left and right speakers 9 and 10 respectively output the reproduced sounds of the left and right channel signals L and R, in which the lower frequency components are given a larger phase delay as described above, and the center speaker 14 adds the left and right channel signals L and R. The reproduced sound of the added signal without any phase delay is output.

As a result, the reproduced sound in the mid-range and low-temperature range, which determines the sound image localization in the sound reproduced from the center speaker 14, is ahead of the reproduced sound in the mid-range and low-temperature range reproduced by the left and right speakers 9 and 10. Since the sound is played back in phase, the listener feels that the sound played from the center speaker with no phase delay arrives before the sound played from the left and right speakers 9 and 10 due to the preceding sound effect.

Therefore, the sound image C to be formed at the center can be localized approximately at the center of the left and right sound images A and B without increasing the volume of the reproduced sound reproduced from the center speaker 14.

At this time, the reproduced sound in the high frequency range, which is unrelated to the sound image localization, is reproduced in the same phase by the center speaker 14 and the left and right speakers 9, 10, so that the sense of spaciousness does not decrease and the listener is placed in a lopsided position. You can get a good stereo feeling even when

Now, if the signal voltage of the central sound image C is e _C and the signal voltages of the left and right channel signals L and R are e _L and e _R , then e _L = e _R = e _C /2.

On the other hand, for example, the signal voltage e _l of the leftmost sound image A is e _L
= e _l , e _R =0, and the signals are distributed to the left and right channels.

The voltage applied to speakers 9, 10, 14
Assuming that e' _L , e' _R , e' _C and the attenuation amount At are k = 10-At/20, for the central sound image C, e' _R = e _C /2, e' _C = K・(e _R +e _L ) = Ke _C , e′ _L = e _C
/
It becomes 2.

For the sound image A at the left end, e′ _R =0, e′ _C =K·(e _R +e _L )=K· _el , and e′ _L = e _l .

If K≒0.32, that is, At=10 dB, for the central sound image C, e'c is 4 dB smaller than e'L,
Also, for sound image A on the left, e′c is greater than e′L.
10dB smaller. That is, although the sound image C in the center is radiated at a level 4 dB lower on the leading sound side, the sound image can be localized near the speaker 14 due to the leading sound effect. Regarding the sound image A at the left end, since the level of the speaker 9 is 10 dB higher than that of the speaker 14, this level difference exceeds the preceding sound effect, so that the sound image can be localized near the speaker 9. Similarly, for sound image B on the far right, the level of speaker 10 is different from that of speaker 14.
10dB higher, and due to this level difference, speaker 1
It is possible to localize the sound image near 0.

The phase lag of the left and right channel signals L and R is adjusted depending on the position of the listener.If the phase lag of the left and right channel signals L and R is made the same, it will be the same whether the listener is at a position off to the right or to the left. You can get a stereo feeling. The phase delay can be easily adjusted, for example, by simply short-circuiting the capacitor C of a predetermined phase shift circuit 15 among the plurality of phase shift circuits 15.

Note that if no phase delay is given to the left and right channel signals L and R, and if no attenuation is given to the sum signal of the left and right channel signals L and R, the two points in Figure 2 indicate that the listening position is to the left. As shown by the chain line, the sound image B at the right end is shifted to the left, and the sound image C at the center is also shifted to the left and the level increases, resulting in reproduced sound that does not provide a sense of spaciousness and stereo as a whole.

Figure 4 shows the overall phase delay amount when 12 stages of phase shift circuits 15 as described above are connected in cascade, which delay the phase by 0 to π depending on the frequency, and the conversion of this phase delay amount into delay time. This figure shows the phase delay amount, which has a total delay amount of 12π due to the 12-stage phase circuit.
In order to shorten the length of the top and bottom of the figure, it is shown folded every 2π.

When converting this phase delay amount into delay time, for example, for a signal with a frequency of 100Hz, it is 2π, that is,
With a delay time of 10ms, which corresponds to the time of one cycle,
Further, the phase delay amount of 8π for the 1KHz signal component becomes a delay time of 1ms×4=4ms, which corresponds to 4 cycles.

As is clear from this figure, the phase delay is larger for lower frequency components, such as approximately 10 ms at a frequency of 100 Hz and approximately 4 ms at a frequency of 1 KHz, and approximately 1 ms or less at high frequencies of 5 KHz or higher for higher frequency components. has a small amount of phase delay.

By the way, since the frequency that determines sound image localization is predominant in the midrange or below, a phase delay time of 4 ms or more in the midrange/low temperature range below 1KHz is a sufficient value to localize the sound image.

On the other hand, sounds played with the same delay time in the high frequency range do not form a composite sound image, but are perceived as two sounds with a time difference, which increases the auditory sense of unnaturalness.
Compared to the case where a signal having a uniform time delay is reproduced regardless of frequency, a more natural sound field can be formed with the configuration of the present application.

FIG. 5 shows the localization data of the central sound image when the pulse waveform is input for each frequency when the delay time is set to 6ms, 8ms, and 10ms. The listening position is near the right speaker 10, as shown in FIG. Also, among each frequency, data 1 indicates where the sound image C that should be localized in the center is actually localized by inputting the left and right channel signals L and R, and data 2 indicates where the right channel signal R is input. The actual localization position of sound image B, which should be localized to the right of the time, is shown.

As is clear from the figure, the sound image C is located approximately at the center. Note that the symbol Γ-〇 in the data indicates that it is localized in the section between the small-diameter Γ mark and the large-diameter 〇 mark, but it is strongly localized on the large-diameter 〇 mark side. For example, when the input frequency is 2 KHz, data 2 shows that the sound is localized in the area between the speaker 14 and the speaker 10, but it is localized strongly toward the speaker 10, that is, to the right.

In the above embodiment, the operational amplifier 16 is used to configure the phase shift circuit 15, but the operational amplifier 16
By using transistors or converting the entire device into ICs, it is possible to reduce costs and make it more compact.

The present invention is not limited to car stereos, but can also be applied to ordinary stereos.

As explained above, in the present invention, by giving a phase delay to the reproduced sound below the middle range that determines the sound image localization of the left and right channels compared to the reproduced sound from the center speaker, the installation interval of these speakers is A special effect is achieved in that a sense of spaciousness can be obtained without increasing the width, and a good stereo feeling can be obtained without deteriorating the sense of spaciousness even when listening from a lopsided position.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional stereo playback device, FIG. 2 is a block diagram showing an embodiment of the present invention, and FIG.
FIG. 4 is a circuit diagram showing an example of a phase shifter, FIG. 4 is a phase delay time characteristic diagram, FIG. 5 is a diagram showing sound image localization data, and FIG. 6 is a diagram showing trial listening positions. 5, 6... Phase shifter, 9, 10... Left and right speakers, 11... Adder, 12... Attenuator, 14...
Center speaker, 15... Phase shift circuit, L, R...
...Left and right channel signals, A, B, C...sound image.

Claims (1)

[Claims] 1. In a stereo reproduction device that includes speakers that reproduce left and right channel signals independently and a center speaker between these left and right speakers, the left and right channel signals are frequency-dependent so that the lower the frequency, the larger the phase delay. The signal is supplied to the corresponding left and right speakers through a phase shifter that causes a phase delay, and the added signal obtained by adding the signals of the left and right channels in the same phase is supplied to the center speaker through an attenuator. A stereo playback device featuring: