JPH0740760B2 - In-car stereo audio system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to an in-vehicle stereo sound device in which a total of four speakers are arranged in front of and in the rear of a vehicle such as a passenger car and for reproducing stereo sound in the vehicle. Regarding

(Summary of the Invention) The present invention has a total of four speakers arranged in front of and behind the vehicle in the left and right, of which a left signal and a right signal are transmitted to the left and right speakers, which are relatively large and have sufficient bass reproduction capability. In the in-car stereo sound device that forms a sound field surrounding the listener by supplying a delayed version of the difference signal of, the low-frequency component below the predetermined frequency of the left and right original signals is extracted, and this low-frequency component is In addition to the delayed difference signal of (3), it is supplied to the rear left and right speakers having a relatively large size and a sufficient bass reproduction capability so that a sufficiently powerful bass sound is reproduced.

(Prior Art) A total of 4 to the left and right in the front and rear of passenger cars and the like.
As one method of an in-vehicle stereo sound device in which three speakers are arranged to reproduce stereo sound in the vehicle, left and right original signals are slightly different from the left and right original signals in the front left and right speakers. Is added to form a natural sound field in which the sound image is localized in the front, and the left and right speakers in the rear are delayed by the difference signal between the left signal and the right signal, or left It has been considered that a signal obtained by delaying the difference signal between the signal and the right signal with some left and right original signals added thereto to form a sound field surrounding the listener.

(Problems to be Solved by the Invention) Except for special vehicles such as buses, passenger cars generally have an engine room and a dashboard in the front of the vehicle, and a trunk room and a trunk in the rear of the vehicle. -The structure has a partition wall between the room and the living space. Due to the structure, a total of four speakers are installed on the left and right in the front and rear of the vehicle. The speaker can be an embedded type or a box type with a size of 16 to 20 cm, which is relatively large and has a sufficient bass reproduction capability, while the left and right front speakers are, for example, a door embedded type with a size of 10 to 13 cm. However, it is unavoidable that the bass reproduction performance is relatively small.

Therefore, as described above, the left and right front speakers are supplied with the original signal or a signal to which a slight difference signal is added, and the left and right rear speakers are delayed with the difference signal or When a signal obtained by adding a small amount of the original signal to the delayed signal is supplied, the low-frequency components below the certain frequency of the left and right original signals are mainly monaural signal components, and the difference signal contains the left and right original signals. Since low-frequency components below a certain frequency are hardly included, the low-frequency sound is hardly reproduced from the left and right rear speakers to which delayed signals of the difference signal are mainly supplied, and the low-frequency sound of the rear left and right speakers is sufficiently low. Reproduction ability will not be exhibited. On the other hand, the front left and right speakers are supplied with an original signal containing a sufficient low-frequency component, but the front left and right speakers are relatively small and have poor bass reproduction capability, so that the front left and right speakers also produce low frequencies. Hardly played. Therefore, as described above, the conventional in-vehicle stereo audio system of the type which supplies the delayed left and right speakers mainly with the delayed difference signal has an advantage that a sound field surrounding the listener is formed. However, there is an inconvenience that the reproduced sound becomes lacking in power with almost no bass.

In view of such a point, the present invention provides a total of four speakers on the front and rear of the vehicle in the left and right, and a left signal and a right signal to the rear left and right speakers, which are relatively large and have sufficient bass reproduction capability. In the in-vehicle stereo sound device that forms a sound field surrounding the listener by supplying a delayed version of the difference signal, the low-pitched sound with sufficient power is reproduced.

(Means for Solving Problems) According to the present invention, a total of four speakers are arranged in front and rear left and right in the vehicle, and in the left and right rear speakers having a relatively large size and sufficient bass reproduction capability. An in-vehicle stereo sound device that supplies a delayed difference signal between the left signal and the right signal to form a sound field surrounding the listener, and in addition to the left and right original signals, the difference signal is added to the left and right front speakers. A low-frequency component of the left and right original signals with a frequency lower than a predetermined frequency is taken out, the low-frequency component is added to the above-mentioned delayed difference signal, and is relatively large and has sufficient bass reproduction capability. To the left and right speakers.

(Operation) In the in-vehicle stereo audio device according to the present invention configured as described above, the low-frequency components below the constant frequency of the left and right original signals are provided to the left and right speakers behind, which are relatively large and have sufficient bass reproduction capability. Is sufficiently supplied, the bass is sufficiently reproduced from the rear left and right speakers, and a sufficiently powerful reproduced sound of the bass is obtained.

(Embodiment) FIG. 1 and FIG. 2 are each an example of an in-vehicle stereo audio system according to the present invention. In both cases, the difference signal is delayed in the rear left and right speakers by switching the switch. A mode in which a low frequency component of a predetermined frequency or lower is added to the original signal, and a signal to which the difference signal is added to the original signal is supplied to the front left and right speakers (hereinafter,
Bass-enhanced surround mode) and a mode in which the left and right original signals are simply supplied to the left and right rear speakers and the front left and right speakers (hereinafter referred to as simple mode)
This is the case where either of the above can be selected.

In the example of FIG. 1, left and right input terminals 10L and 10R are supplied with left and right original signals L and R obtained from a vehicle-mounted cassette tape recorder, a compact disc player, or the like.

The left and right original signals L and R obtained at the input terminals 10L and 10R are supplied to the subtraction circuit 21, and the left and right original signals L and R are supplied from the subtraction circuit 21.
Difference signal L-R is obtained. This difference signal LR is at terminal c
Is supplied to the terminal n of the mode changeover switch 22 which is switched to either side of the terminal n and the terminal f, and in the bass enhancing surround mode, the terminal c of the switch 22 is switched to the side of the terminal n and the terminal of the switch 22 is changed. The difference signal L-R is taken out at c.

The difference signal L-R obtained at the terminal c of the switch 22 is supplied to the low-pass filter 23, and the low-pass filter 23 produces a component (LR) x below the frequency of the difference signal L-R, which will be described later.
Is obtained. The difference signal (LR) x is supplied to the delay circuit 24 composed of a BBD (bucket brigade device), and the clock is supplied from the clock generation circuit 25 to the delay circuit 24. The difference signal (LR) x is delayed, the output of the delay circuit 24 is supplied to the low-pass filter 26, and the delayed difference signal (LR) d is obtained from the low-pass filter 26. The low-pass filter 23 is provided in order to prevent malfunction of the BBD that constitutes the delay circuit 24.
The band of the input signal of BD is limited, and the low-pass filter 26 is for reducing clock noise due to BBD.

The delay time of the delay circuit 24 is set to about 15 to 30 msec, for example, 20 msec. To use a BBD with a capacity of 512 bits and set the delay time to 20 msec, the clock frequency should be set to 25.6 kHz, in which case the BBD can play a band of 1 to 3
Therefore, the cutoff frequency of the low-pass filters 23 and 26 is set to, for example, 2 kHz.

The delayed difference signal (L
-R) d is supplied to the inverting circuit 27, and the delayed difference signal (RL) d in the inverted state with respect to the delayed difference signal (LR) d is obtained from the inverting circuit 27, The delayed difference signal (L-
R) d and (RL) d are supplied to the adding circuits 28L and 28R.

Further, the left and right original signals L and R obtained at the input terminals 10L and 10R are supplied to the low-pass filters 29L and 29R, and the low-pass components Ll below the predetermined frequency of the left and right original signals L and R are supplied from the low-pass filters 29L and 29R. , Rl is taken out.

Considering the reproduction of vocals, the low frequency components Ll and Rl to be supplied to the rear left and rear right speakers as described later.
If the band is relatively wide (300 to 400 Hz or less), the sound image will not be localized in the front, so the low frequency components Ll, Rl
The band is set to 250 Hz or less. Therefore, it is desirable to set the cutoff frequency of the low pass filters 29L and 29R to 250 Hz. However, if the forward localization of the sound image is not a problem, the band of the low frequency components Ll and Rl may be set to 300 to 400 Hz or less. The level of the low frequency components Ll, Rl is the above-mentioned delayed difference signal (LR) d, (RL) to which the low frequency components Ll, Rl are added.
It does not have to be the same as the level of d, but rather the low frequency component L
It is desirable to increase the levels of l and Rl.

250Hz obtained from this low-pass filter 29L, 29R
The following left and right low-frequency components Ll, Rl are supplied to the adder circuits 28L, 28R, and in the bass boost surround mode, the adder circuit 28L,
The difference signal (LR) d, (RL) delayed at 28R
The left and right low-frequency components Ll and Rl are added to d, and addition circuits 28L and 28R are added.
Is supplied to the respective terminals n of the mode changeover switches 31L and 31R similar to the switch 22 described above. Also,
Left and right original signals L and R obtained at input terminals 10L and 10R are switches
It is supplied to each terminal f of 31L and 31R.

On the other hand, the left and right original signals L and R obtained at the input terminals 10L and 10R are supplied to the adding circuits 32L and 32R. Further, in the bass boost surround mode, the difference signal LR obtained at the terminal c of the switch 22 is supplied to the inverting circuit 33, and the difference signal LR from the inverting circuit 33 is inverted with respect to the difference signal LR. The signal RL is obtained, and the difference signals LR and RL are supplied to the attenuation circuits 34L and 34R, and the difference signals a (LR), a of some level are supplied from the attenuation circuits 34L and 34R. (RL) is obtained, and this difference signal a
(LR), a (RL) is supplied to the adder circuits 32L, 32R, and difference signals a (LR), a (R-R) are added to the left and right original signals L, R in the adder circuits 32L, 32R. L) is added.

Between the terminal c of the switch 31L and the terminal c of the switch 31R, and between the output end of the adder circuit 32L and the output end of the adder circuit 32R, interlocking for adjusting the balance of the rear and front left and right reproduction outputs. The level adjusters 41 and 42 that are adjusted by the control circuit are connected to the left and between the output end of the adder circuit 32L and the terminal c of the switch 31L and between the output end of the adder circuit 32R and the terminal c of the switch 31R. The level adjusters 43 and 44, which are adjusted in conjunction, are connected for adjusting the balance of the front and rear reproduction outputs.

Then, the signals obtained at the respective terminals c of the switches 31L and 31R pass through the output amplifier circuits 51L and 51R, and the rear left and rear right speakers are relatively large and have a sufficient bass reproduction capability.
The signals supplied to the 61L and 61R and obtained from the adder circuits 32L and 32R are smaller than the rear left and rear right speakers 61L and 61R through the output amplifier circuits 52L and 52R, and the bass reproduction capability is inferior. It is supplied to the right speakers 62L and 62R.

In the above configuration, when the bass boost surround mode is set, the terminals c of the switches 22 and 31L, 31R are switched to the respective terminals n side, and the rear left and rear right speakers 61L, 61R are The delayed difference signal (LR) d, (R) obtained from the low-pass filter 26 and the inverting circuit 27.
-L) d is added with the left and right low-pass components Ll, Rl obtained from the low-pass filters 29L, 29R, and
The front left and front right speakers 62L, 62R have input terminals 10L, 1
A signal obtained by adding difference signals a (LR) and a (RL) of a slight level to the left and right original signals L and R obtained at 0R is supplied. Therefore, not only a sound field surrounding the listener but also the rear left and rear right speakers 61L, 61
R creates a powerful sound field that produces a sufficient low tone.

Also, when switching to the simple mode, switch 22 and 31L,
The respective terminals c of the 31R are switched to the respective terminals f side, the left and right original signals L and R are obtained at the respective terminals c of the switches 31L and 31R, and the left and right original signals are also obtained from the adder circuits 32L and 32R. L and R are obtained, so rear left and rear right speakers 6
The left and right original signals L and R are respectively supplied to the 1L and 61R and the front left and front right speakers 62L and 62R, so that a sound field in which left and right sounds are simply obtained from the rear and the front is formed.

In the example of FIG. 2, the left and right original signals L and R obtained at the input terminals 10L and 10R are supplied to the adder circuit 11, and the adder circuit 11 obtains the sum signal L + R of the left and right original signals L and R, This sum signal L +
R is supplied to the low-pass filter 29, and from the low-pass filter 29, the sum signal L + R has a predetermined frequency or less, for example, 250 Hz.
The following low-frequency component Ml is extracted, and this low-frequency component Ml is the first
In the example of the figure, instead of the left and right low-pass components Ll and Rl obtained from the low-pass filters 29L and 29R, they are supplied to the adder circuits 28L and 28R, respectively, and the delayed difference signals (L -R) d and (R-L) d are added respectively, and the others are the same as in the example of FIG.

The low-frequency components Ll and Rl in the example of FIG. 1, which are low-frequency components below the predetermined frequency of the left and right original signals L and R, are mainly monaural signal components, so the low-frequency component Ml obtained from the low-pass filter 29 is The low-frequency components Ll and Rl in the example of FIG. 1 are almost the same, and the operation of the example of FIG. 2 is similar to that of the example of FIG. 1 and the same effect is obtained.

Although not shown, difference signals L-R and RL of left and right original signals L and R are obtained from left and right original signals L and R, and these difference signals L-R and RL are separated. Alternatively, the delayed difference signals (LR) d and (RL) d, which are delayed by the delay circuit of FIG.

In the above example, it is premised that the left and right rear speakers are relatively large and have sufficient bass reproduction capability due to the structure of the car, and the left and right front speakers are relatively small and inferior in bass reproduction capability. It is what

(Effects of the Invention) According to the present invention, the left and right loudspeakers at the rear, which are relatively large and have a sufficient bass reproduction capability, have a difference between the left signal and the right signal and a difference between the left and right original signals. Since a low-frequency component below a predetermined frequency is added, the bass is sufficiently reproduced from the rear left and right speakers that are relatively large and have sufficient bass reproduction capability, and a sufficiently powerful bass reproduction sound is produced. can get.

[Brief description of drawings]

1 and 2 are connection diagrams showing an example of an in-vehicle stereo sound device according to the present invention. In the figure, 10L and 10R are input terminals for the left and right original signals, 22 and 31
L and 31R are mode selector switches, 24 is a delay circuit, 29L, 29R and 29 are low-pass filters, and 61L, 61R, 62L and 62R are rear left, rear right, front left and front right speakers.

Claims (1)

[Claims] 1. A front left and right speaker, which is respectively arranged on the left and right in front of the vehicle, and a rear left and right speaker, which is larger than the front left and right speaker and is excellent in low-frequency sound reproduction capability, arranged on the left and right behind the vehicle, respectively. A first circuit for obtaining a difference signal between the left signal and the right signal from the first circuit, a second circuit for delaying the difference signal obtained from the first circuit, and a low-frequency component of a predetermined frequency or less of the left and right original signals. A third circuit for taking out, and a fourth circuit for reducing the level of the difference signal obtained from the first circuit and adding to the left and right original signals, and supplying the added signal to the front left and right speakers. A fifth circuit that adds the low-frequency component obtained from the third circuit to the delayed difference signal obtained from the second circuit and supplies the obtained addition signal to the rear left and right speakers. Equipped with In-vehicle stereo sound system.