JPS62258599A - On-vehicle surrounding device - Google Patents

Abstract

PURPOSE:To prevent the feeling of deficient low frequency sound by inserting a high pass filter to the prestage of an attenuator so that the frequency range of components subtracted from signals L, R is limited to the middle and high frequency sound. CONSTITUTION:The on-vehicle 4-speaker system consists of front side speakers FL, FR and rear side speakers RL, RR and high pass filters HPF1, HPF2 are inserted to the prestage of attenuators ATT1, ATT2. The input resistor R1 is used for the high pass filter HPF1 and the cut-off frequency fc is expressed as fc<10>=1/2piC1'R1. When the f'c is 200Hz, C1' is 7.96X 10<-8>, it is realized by the capacitor of 0.0082muF. In using the circuit, no subtraction is executed at a low sound frequency below 200Hz. Even when the rear side speakers RL, RR with excellent low sound reproduction capability are used, the low frequency sound is not deficient.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a vehicle-mounted surround device with improved bass range.

[Conventional technology]

A typical four-speaker system for cars has two speakers on each side of the front instrument panel and two speakers on each side of the rear package tray board. When an in-vehicle surround system is configured using this four-speaker system, the front speakers play back the signal that determines the sound image localization direction of the original signal, and the rear speakers play the surround signal that gives a sense of encirclement and widening. can be played.

Figure 5 is an example, where FL and FR are left and right front speakers, RL and RR are left and right rear speakers, and OP +
, OP2 is a subtraction circuit using an operational amplifier, and ATT + and ATT2 are attenuators for attenuation.

Considering the performance difference between the front and rear sides of the vehicle interior, one of the biggest differences is bass reproduction ability. The front side speakers FL and FR are generally small, about 10 cm due to space constraints, and the panfuru effect is insufficient on both sides of the instrumental panel, and as shown in Figure 4 (al) The bass reproduction ability of the following is often inferior.On the other hand, the rear speaker RL.

In RR, it is often possible to install up to a relatively large one such as 16 (about 1), and if the trunk room is used as a back cavity, the same figure price can be used, and it is possible to sufficiently reproduce bass frequencies of 100 Hz or less. .

On the other hand, in the surround system shown in Fig. 5, the surround signals L-kR and R-kL are created by subtracting two signals from the R signal from a normal two-channel stereo signal, but at this time, the frequency of the general music source is 100 to 200 Hz or less. Because there is relatively little level difference or phase difference between the two signals in the bass range,
Due to the subtraction, the energy in this band is reduced (and, since this surround signal is reproduced from the rear speakers RL and RR, which originally have excellent bass reproduction ability, compared to when performing normal 2-channel stereo reproduction as a whole) There is a problem that the bass range is insufficient.

[Problem that the invention seeks to solve]

The above-mentioned problem is caused by the input method of the subtraction circuit used in conventional surround sound devices. Figure 6 is a circuit diagram of the main parts of this surround device.R1 and R3 are the input resistances of the subtraction circuit OP+, R2 is the sweeping resistance, R4 is the bias resistance, and C+
, C= is a coupling capacitor, and Va is a bias voltage. The amount of subtraction is determined by the values of R1-R4.

In this figure, the transfer function G (51) seen from the R input side that provides the signal to be subtracted is expressed by the following equation.

Also, the cutoff frequency fc is fo=...song...(2
)2πC+R+. Generally, fc is often set to a low frequency. For example, if G (S) at a sufficiently high frequency is about 0°7 and R2 = 6.8 (KΩ), then R+ = 10 (
K, Q). Here, in order to make fc less than 10 (R2), it becomes as follows, so 2.2 μF is used for C+ as a component.

The reason why fc is set to a low frequency in this way is that it is intended to be outside the audible frequency band. Therefore, since even such a low range is subject to subtraction, the problem of insufficient low range occurs as described above. The present invention attempts to improve this point.

[Means for solving problems]

FIG. 1 is a basic configuration diagram of the present invention, where FL and FR are front speakers, RL and RR are rear speakers, OPI, O
F2 is a subtraction circuit, ATT+, ATT2 is an attenuator, H
PF+ and HPF2 are bypass filters.

[Effect]

The surround device in Figure 1 is connected to the attenuator ATT in Figure 5.
+, bypass filter HPFI in front of ATT2,
This is the one with HPF2 inserted. Therefore, the frequency ranges of the components kR and kL to be subtracted from the signal R are limited to the middle and high ranges, and the low ranges that do not pass through the filters HPFI and HPF2 are not subject to subtraction. Therefore, the feeling of lack of low frequency range caused by using a surround device can be eliminated.

〔Example,〕

FIG. 2 is a circuit diagram of a main part showing an embodiment of the present invention.
kR) shows the subtraction circuit on the side that obtains the output (the same goes for the other side). In this example, the coupling capacitor C1 in FIG. 6 is replaced with a capacitor C+' which is passed through to form a bypass filter HPF+. This filter H
PF + uses an input resistor R1, and has a cutoff frequency fc. If this fc' is 200Hz, C,'== = 7.96x
1O-8(F)2r x 200 x 10 x 1
03, which can be realized with a 0.0082 (μF) capacitor.

If this circuit is used, subtraction will not be performed in the low frequency range below 200 Hz. Therefore, even if the rear speakers RL and RR, which have excellent bass reproducing ability, are used for surround sound, there will be no shortage of bass. In addition, bypass filters HPF+, HPF2
may be formed independently, but if it is constructed from the input impedance RI of the subtracting circuit and the coupling capacitor C+', there is an advantage that the number of parts is reduced and C+' can have a small capacitance.

FIG. 3 is a block diagram showing a modification of the present invention. This example is a method of performing delayed signal processing on one system of surround signals, but in this case as well, if a bypass filter HPF is placed in front of the negative input side of the subtraction circuit OP, the same effect as in the above-mentioned example can be expected. can.

〔Effect of the invention〕

As described above, according to the present invention, (1) in an in-vehicle surround device, even if the rear speakers with excellent bass reproduction ability are used for surround sound, there will be no lack of bass; (2) the input of the subtraction circuit; If the HPF is configured with an impedance and a compensating capacitor, there is an advantage that a coupling capacitor with a smaller capacity than the conventional one can be used.

[Brief explanation of drawings]

Fig. 1 is a basic block diagram of the present invention, Fig. 12 is a main circuit diagram showing an embodiment of the invention, Fig. 3 is a block diagram showing a modification of the invention, and Fig. 4 is a car speaker. Figure 5 is a block diagram of a conventional surround device, Figure 6 is a frequency characteristic diagram of
The figure is a circuit diagram of the main part. In the figure, OP, OPI, and OP2 are subtraction circuits, ATT +
, ATT2 is an attenuator, HPF, HPF +. HPF 2 is a bypass filter, C+' is a coupling capacitor, RI is an input resistor, FL and FR are front speakers, and RL and RR are rear speakers. Applicant: Fujitsu Ten Ltd. Representative Patent Attorney Minoru Aoyagi June Basic Pro Tsukuy Diagram 1 ↓ We fc=Cho Shibon 5! Schematic diagram of Akinomi #'l Figure 2 Unexploded August t Responsibility 1 blow 7 diagram ω) Front side + oo + KIOKIJ 1n IζΣ) Father (Hz) (b)
The IIT side speaker's praises +! ! Mouth Figure 4

Claims (2)

[Claims] (1) In a car surround device equipped with a subtraction circuit that creates a surround signal by subtracting one of the stereo signals from the other, the signal is applied to the subtraction side input of the subtraction circuit through a bypass filter. Features of car surround equipment. (2) The in-vehicle surround device according to claim 1, wherein the bypass filter is formed by an input impedance on the subtraction side of the subtraction circuit and a coupling capacitor.