JPH0328638Y2 - - Google Patents

Description

[Detailed description of the invention] <Industrial application field> With the recent spread of video tape recorders (VTRs), video discs (VDs), and project-type televisions into general households, they have been used as so-called home entertainment, or as There is a strong tendency for people to enjoy theatrical movies at home as a home theater. The present invention relates to a matrix four-channel decoder that reproduces four channels using two transmission systems in a surround stereo sound reproduction system that is often used for sound field reproduction in such cases.

<Prior art and its problems> A very common type of surround 4-channel system is a discrete 4-channel system that combines a 4-channel decoder and 4-channel playback with 4 speakers and 4 amplifiers. However, this system not only requires four amplifiers (four channel amplifiers), but also requires a complicated control circuit to overcome poor channel separation, making the entire system extremely expensive.

Therefore, from an economical point of view, speaker matrix type 4 channel decoders have come into widespread use because they can provide matrix 4 channel reproduction by simply connecting speakers. An example of this is the book published by Nikkan Kogyo Shimbun on October 20, 1971, pages 53 to 4 channel stereo.
It is described on page 54. As shown in Fig. 5, the left and right front speakers LF and RF are directly connected to the channel output terminals +L, -L and +R, -R of the decoder D, respectively, and the left and right rear speakers LB and RB , connect the same polarity terminals of one of them and connect their common connection point Y
is connected to the connection point X between the output terminals -L and -R of the decoder D via a blend resistor VR for varying the matrix coefficient of the rear channel. When the resistance value of the blend resistor VR is set to infinity (open), reproduction close to a pseudo 4 channel can be performed in which difference signal components such as L-R and R-L are output from the rear speakers LB and RB. , the matrix coefficient of the rear channel approaches -1. On the other hand, if the resistance value of the blend resistor VR is decreased so that it approaches zero, the matrix coefficient of the rear channel will also approach zero, and the same sound as the front channel will be produced, resulting in channel separation between the front and rear channels. becomes worse. In other words, the overall sound image localization is poor. In addition, in many recording systems, the low frequency components have recording characteristics close to monaural, so conventional speaker matrices 4 with the above-mentioned configuration where the volume of the rear channel is originally smaller than the volume of the front channel. As for the channel decoder, the reproduction of bass frequencies from the rear speakers LB and RB was extremely insufficient, which had the drawback of significantly detracting from the sense of realism.

In other words, in the case where only the blend resistor VR is connected, the frequency characteristic of the decoder output is
As shown by the dotted line in the figure, the level remains flat from the bass to the treble range, and the level only changes depending on the value of the blend resistance VR. Therefore, as mentioned above, if you play back a recorded source with the bass level suppressed, a lot of the high frequency range will be played from the rear speakers LB and RB, and most of the low frequency range will be played from the front speakers LF and RF. As a result, the overall balance between high and low frequencies was disrupted, leaving the listener feeling unsatisfied.

In view of these circumstances, the present invention is economical, allows the rear speakers to reproduce a sufficiently rich range of bass frequencies, and reduces noise in the treble range, resulting in 4-channel playback with an overall sense of realism. The purpose is to provide a possible decoder.

<Means for solving the problems> The matrix 4-channel decoder according to the present invention devised to achieve the above purpose has the following features:
As shown in Fig. 1, the example is the connection of the output terminals -L, -R of each channel output terminal +L, -L and +R, -R to which the left and right front speakers LF, RF are directly connected, respectively. Point It is characterized by its structure.

<Operation and Effects of the Invention> When using the matrix 4 channel decoder of the present invention having such a characteristic configuration, the high frequency range is attenuated due to the frequency/impedance characteristics of the series resonant circuit of the capacitor C and the coil L. The sound range peaks around a certain frequency, and both higher and lower frequencies exhibit a characteristic of attenuation with a slight degree of attenuation, but overall the bass range exhibits characteristics that are enhanced (low boost). I will do it. Incidentally, the characteristic curve shown by solid lines 1 to 5 in Figure 2 is the case when a series resonant circuit with coil L = 8.44 mH / 1.75 Ω and capacitor C = 500 μF is used, and the resistance value of blend resistor VR is changed in 5 steps. The output frequency characteristics of the decoder of this invention have a maximum value around 80Hz, and frequencies higher than that,
A characteristic of attenuation of about 3 dB per octave is obtained on either side of the low frequency. Therefore, by inputting the selectively boosted output, such as around 80 Hz, to the rear speakers LB and RB, sufficient low frequency reproduction from the rear speakers LB and RB can be achieved. At the same time, by changing the resistance value of the blend resistor VR, the output of the treble range can be adjusted considerably, making it possible to effectively reproduce the treble range, where noise is particularly problematic, while sufficiently suppressing noise. It is.

Overall, the present invention maintains the economical effect of requiring only a simple speaker connection, while providing a sufficiently rich bass range reproduction and noise reduction, even if the recording is close to monaural. By reproducing the high frequency range, we were able to reliably achieve realistic 4-channel stereophonic sound reproduction.

FIG. 3 shows another embodiment, in which two of the series resonant circuits of a coil L and a capacitor C are connected.
Both are connected in parallel to the blend resistor VR. In this case, the coil L of one circuit is 8.44 mH/1.75Ω, the capacitor C is 500 μF, and the coil L ₁ of the other circuit is 8.57 mH/ 1.81Ω,
If capacitor C ₁ = 1.650μF, blend resistance
The output frequency characteristics when the resistance value of VR is changed to five levels are shown in Figure 4. As is clear from FIG. 4, by using two or more series resonant circuits, there is an effect of not only boosting the bass range but also flattening the reproduction characteristics of the boosted bass range.

[Brief explanation of the drawing]

Figure 1 is a conceptual diagram showing one embodiment of the present invention;
The figure is an output-frequency characteristic diagram when Lch and Rch in-phase input is applied, FIG. 3 is a conceptual diagram showing another embodiment, and FIG. 4 is an output-frequency characteristic diagram when Lch and Rch in-phase input is the same as shown in FIG. FIG. 5 is a conceptual diagram of the conventional one. LB, RB...Rear speaker, LF, RF...Front speaker, VR...Blend resistance, C...
...Capacitor, L...Coil, X...Output terminal -
Connection point of L and -R, Y... Common connection point of same polarity terminals of rear speakers.

Claims (1)

[Scope of claim for utility model registration] Each channel output terminal + to which the left and right front speakers LF and RF are directly connected, respectively.
L, -L and +R, -R same polarity output terminal -L,
-R or +L, +R connecting point A speaker matrix 4-channel decoder connected via VR, and between both connection points
A matrix 4-channel decoder characterized in that a series resonant circuit consisting of a capacitor C and a coil L for enhancing low frequency range is connected in parallel to the VR. A matrix four-channel decoder according to claim 1, which is provided with a plurality of series resonant circuits each including the capacitor C and the coil L.