GB2099664A

GB2099664A - Device for producing a multi- channel signal from a stereo signal

Info

Publication number: GB2099664A
Application number: GB8134182A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-11-12
Filing date: 1981-11-12
Publication date: 1982-12-08
Also published as: GB2099664B

Abstract

A device for producing a multi- channel signal from a stereo signal consists of an electric base part (1), e.g. a coil, resistor, or capacitor, or a combination thereof, across which a stereo signal (L, R) is connected to act, and a plurality of taps (5) which are connected to the base part and from which output signals for speakers (2) are taken. The taps, whose number is arbitrary, can be connected to the base part at arbitrary spacings. The location of the loudspeakers in the listening space is also arbitrary, individual instruments appearing most strongly at the tap where their L and R channel signals are cophasal, whereby the location of the instruments in an orchestra can be imitated and a three- dimensional effect be obtained. Amplifiers may be connected between the taps and the speakers (2). <IMAGE>

Description

SPECIFICATION Device for producing a multi-channel signal from a stereo signal The present invention relates to a device for producing a multi-channel signal from a stereo signal, said device being applicable with stereophonic sound reproduction systems.

A general object in the development of sound reproduction systems is to obtain a more natural reproduction. This object is aimed at, on one hand, by improving the technical properties of devices and, on the other hand, by developing different reproduction systems. An established reproduction system is a two-channel, i.e. a stereophonic sound reproduction system in which the signal is reproduced through two individual channels.

The basic starting point in a stereo system is that the music is received with two microphones whereby the signals from the individual instruments arrive at the microphones at slightly different times because of the different distances between the instruments and the microphones.

When the signals so received then are reproduced through two loudspeakers located in the base point of an isosceles triangle and belonging to a conventional stereo system, a listener positioned at the apex point of this triangle hears these sounds also at slightly different times whereby he has the perception that the sound comes from a point between the loudspeakers. However, such a conventional stereo system contains factors which impair the naturalness of the sound reproduction. One essential disadvantage is the small size of the area at the apex point of said triangle where the stereophonic reproduction impression is obtained. Another disadvantage is that the two-channel system, even though said channels would contain all essential sound signals, limits the signals to two sound reproduction paths whereby weak signals tend to become subdued by louder signals.

In order to eliminate the above-mentioned disadvantages various solutions have been developed, for example, a four-channel system and a system utilizing also the difference signals from the stereo channels. The four-channel system, which of course improves the naturalness of sound reproduction, is not widely used because of the complicated and expensive devices it requires. In fact, it requires in principle twice as many devices as a stereo system. Moreover, the four-channel system does not offer any substantial advantages as compared to a conventional stereo system when aiming at a natural sound reproduction.

A somewhat more natural end result has been obtained in a sound reproduction system in which three loudspeakers are used and in which a mono signal produced by combining the stereo signal channels is fed to the loudspeaker of the highest efficiency and the difference signals between the channels are fed to the two smaller loudspeakers located at the sides of the listening space. Neither is the listening space in such a system as limited as in a conventional stereo system. Yet even this system does not produce a sound reproduction that could be called natural.

Thus, the object of the present invention is to provide a device which, starting from a stereophonic sound signal, provides a sound reproduction system which produces a very natural reproduction and eliminates the disadvantages and limitations associated with the above-mentioned systems and a conventional stereo system.

This has been accomplished by means of a device according to the invention for producing a multi-channel signal from a stereo signal, said device being characterized in that it consists of an electric base part, over which a stereo signal is connected to act, and of a plurality of taps which are connected to the base part and from which output svgnals are taken.

As the electric base part can be used, e.g., a coil, a resistor, or a capacitor, over which the channel signals of the stereophonic system are connected to act. The multi-channel signals are obtained from between the taps connected to this base part and ground. These taps can be connected to the base part at arbitrary spacings, and because the number of taps is not limited, the number of channels produced in arbitrary.

The construction and operation of the present invention will be described in more detail in conjunction with the accompanying drawings in which Figure 1 shows a connection in which the electric base part is a resistor or a coil, and Figure 2 shows a connection in which the base part is connected to the stereo system before the output stage.

In Figure 1, electric base part is indicated with reference numeral 1, and to its poles are connected the left L and the right R signal channel of a stereophonic system. In this embodiment, loudspeakers 2 are connected directly between taps 5 connected to a resistor or to a coil 1 and the minus pole of the channels L and R.

In Figure 2, the base part also comprises a coil or a resistor 1 which is positioned in the stereo system before the output stage whereby each signal channel produced has its own amplifier 3 which amplifies the signal before it is fed to the loudspeaker 2.

The operation of the invention is based on the fact that, in a stereophonic signal, as stated already earlier, the signal of the same instrument has a minor time difference between the channels.

When these signals are fed to the devices according to Figures 1 and 2, the result is that these signals are cophasal at some point of the base part which corresponds to the location of the instrument in the recording situation whereby this signal can be transferred to the output channel connected to this point. When these channels, the number of which can be arbitrary, either directly or amplified are fed to the loudspeakers 2, which are positioned in a semi-arch resembling of the positioning of the orchestra, this amplified signal will be heard louder from a certain point in this semi-arch than from elsewhere. In this way, the signals from the individual instruments contained in the stereo signal can be distributed to the various points in the semi-arch in a manner corrresponding to the location of the instruments in the original playing situation.This results in an extremely natural sound reproduction which is quite independent of the point of listening.

This impression can be further improved, especially, if the location of the individual instruments in the original playing situation is known, by positioning the loudspeakers in a corresponding manner closer to or farther away from the listener whereby a three-dimensional effect is produced. Such a location of the loudspeakers is very advantageous in bigger rooms and is particularly well applicable to symphonic music because the positioning of instruments in a symphony orchestra is quite constant.

The device according to the invention can be connected to any point in a stereophonic sound reproduction system in which the channels for the stereophonic signal already are spaced apart.

However, most preferably, it is positioned after the output stage because in this case separate output stages are not required for each signal produced. By appropriately dimensioning the device according to the invention it is also easy to adapt the impedance of the device such that it does not interfere with the operation of the end amplifiers. When high outputs are required, it is, however, necessary to amplify each channel produced separately, as shown in Figure 2.

Claims

1. A device for producing a multi-channel signal from a stereo signal, characterised in that it consists of an electric base part, over which, in operation, a stereo signal is connected to act, and of a plurality of taps which are connected to said base part and from which output signals are taken.

2. A device as claimed in claim 1, characterised in that said base part is a coil, a resistor or a capacitor, or a combination thereof.

3. A device as claimed in claim 1 or 2, characterised in that said taps are located at arbitrary spacings.

4. A device as claimed in claim 1, 2 or 3, characterised in that the number of said taps and channels so produced is arbitrary.

5. A device as claimed in any preceding claim, characterised in that said taps are connected to loudspeakers either directly or through amplifiers.

6. A device as claimed in claim 5, characterised in that the location of said loudspeakers in the listening space is arbitrary, whereby the location of the instruments in an orchestra can be imitated and a three-dimensional effect be obtained.

7. A device for producing a multi-channel signal from a stereo signal, substantially as hereinbefore described with reference to Figure 1 of the accompanying drawings.

8. A device for producing a multi-channel signal from a stereo signal, substantially as hereinbefore described with reference to Figure 2 of the accompanying drawings.