GB1604766A

GB1604766A - Sound reproduction systems

Info

Publication number: GB1604766A
Application number: GB2269078A
Authority: GB
Original assignee: ARD TECH ASS ENG
Current assignee: ARD TECH ASS ENG
Priority date: 1978-05-25
Filing date: 1978-05-25
Publication date: 1981-12-16

Description

(54) IMPROVEMENTS IN OR RELATING TO SOUND REPRODUCTION SYSTEMS (71) We, A.R.D. TECHNICAL ASSIS TANCE & ENGINEERING SERVICES INTER NATIONAL ANSTALT, of P.O. Box 34613, 9490 Vaduz, Leichtenstein, a body corporate organised and existing under, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to a sound reproduction system.

The invention is concerned with the provision of a sound reproduction system capable of providing stereophonic sound, in which means is provided for diminishing the possibility of a split sound image due to spaced loudspeaker stations.

In accordance with the invention there is provided a sound reproduction system comprising means for reproducing left and right hand stereophonic signals as sound over substantially the entire audio frequency range at respective ones of a pair of spaced apart outer loudspeaker stations, and means for reproducing as sound only the lower frequency portions of the signals at respective ones of a pair of inner loudspeaker stations.

The invention also provides a method of reproducing stereophonic signals extending over substantially the entire audio frequency range as sound, the method comprising the steps of supplying substantially the entire signals to respective ones of a pair of spaced apart outer loudspeaker stations, and supplying the lower frequency part of the signals only to respective ones of a air of inner loudspeaker stations located et- ween the outer pair.

The invention is further explained below, by way of example with reference to the accompanying schematic drawing, in which: Figure 1 shows a first sound reproduction system embodying the invention; and Figure 2 shows a second sound reproduction system embodying the invention.

In the system of Figure 1, two electric sound signals stereophonically representing an original sound source are reproduced as sound by means of four loudspeaker stations positioned as shown, with loudspeaker stations 1 and 2 spaced well apart' for example, with their centres two or three metres apart, and loudspeaker stations 3 and 4 grouped together at a position midway or approximately midway between stations 1 and 2.

The stereophonic signals are supplied to the loudspeaker stations I and 2 from a source 5, which may be any appropriate source of such signals, for example, a phonographic source, a tape deck or a stereophonic radio receiver. lhe source may contain appropriate control and amplification means for the signals, but such means can be additionally or alternatively located in or adjacent the loudspeaker stations.

To minimise the sensation of spaced sound sources which can result from the basic stereophonic arrangement so far described, sound in the lower part of the audio frequency range only is reproduced in the central region between the loudspeaker stations 1 and 2, by means of the loudspeaker stations 3 and 4. The signals obtained from the source 5 will normally cover substantially the whole of the audio frequency range, and the "gap" effect resulting from the spacing of the stations 1 and 2 cannot be overcome by reproducing the whole of this frequency range centrally without destroying the stereophonic effect.

By reproducing only signals in the lower part of the frequency range, say, below 300 Hz, centrally, the stereophonic effect is preserved, because the lower frequency sounds have much less distinctly directional characteristics than sounds in the upper part of the frequency range. Accordingly, the signals from the source 5 are supplied to the loudspeaker stations 3 and 4 through respective passive or active filters 6, 7 so that these two central loudspeaker stations reproduce substantially only signals below a predetermined frequency.

The limltation of the sound output of the loudspeaker stations 3 and 4 can of course be achieved in other ways, for example by arranging that the loudspeaker units at those stations are capable of reproducing only sounds in the lower frequency range; the signals supplied to the stations 1 and 2 can then be supplied directly also to the stations 3 and 4 respectively.

The system of Figure 1 of course reproduces the lower frequency portion of each of the stereophonic signals at both the inner stations 3 and 4 as well as at both stations 1 and 2.

Figure 2 shows a second sound reproduction system in accordance with the invention in which a source 15 provides stereo signals to respective spaced loudspeaker stations 11. 12. As in the system of Figure 1, these signals are passed through passive or active filters 16 and 17 respectively, so that the lower frequency range only is supplied to respective loudspeaker stations 13, 14 positioned generally centrally between the stations 11, 12. However, in Figure 2 a fifth loudspeaker station 18 is positioned between the loudspeaker stations 13, 14 and the source 15 supplied to this station 18 a third signal to be reproduced as sound by the station 18 alone.

The third signal can be derived from the sound source that provided the two stereophonic signals, for example, from a soloist or group of soloists performing with an orchestra, the sound of which is mainly carried by the stereophonic signals. If so, there will normally be parts of the third signal present in each of the stereophonic signals and vice versa. Instead, the third signal may be from a separate source, for superimposition on the sound obtained from the stereophonic signals. In either event, the provision of the third channel through the loudspeaker station 18 permits the reproduction of the third signal to be controlled independently of the stereophonic signals; appropriate control means are provided at tie source or in association with the source 15 and/or at the loudspeaker stations or some of them.

In the system of Figure 2, the source 15 will not normally be conventional, in as far as it has to produce three signals which however related are essentially different.

The third signal can of course be multiplexed with one or other of the stereophonic signals, but can of course be derived from a special track on a magnetic tape.

Although in Figure 2, the loudspeaker stations it, 14, 18 are shown as separate cabinets positioned side by side, the loudspeaker units of these stations can be housed in a single cabinet or the cabinets differently arranged for example so that the cabinet of station 18 overlies those of stations 13 and 14.

Each of the loudspeaker stations mentioned so far can comprise at a minimum a single suitably mounted speaker unit. At least the loudspeaker stations 1, 2 and 11, 12 however, in order that they shall adequately reproduce sound over substantially the whole audio frequency range, preferably comprise a plurality of loudspeaker units to which the incoming respective stereophonic signal can be distributed through a crossover network. It is however preferred to eliminate the distortions inherent in the use of crossover networks by the use of a multi-channel system, by which each signal is divided into at least two sub-signals each extending substantially only within a respective frequency range, the sub-signals being supplied to respective loudspeaker units within the associated inner and/or outer loudspeaker stations.The third signal can be treated similarly, the loudspeaker station 18 having an appropriate plurality of separate loudspeaker units.

Reference is made to Application 8 100 235, (Serial No. 1 604 767), divided from the present application.

WHAT WE CLAIM IS: 1. A sound reproduction system comprising means for reproducing left and right hand stereophonic signals as sound over substantially the entire audio frequency range at respective ones of a pair of spaced apart outer loudspeaker stations, and means for reproducing as sound only the lower frequency portions of the signals at respective ones of a pair of loudspeaker stations.

2. A system as claimed in claim 1 wherein the pair of inner loudspeaker stations are positioned in adjacency.

3. A system as claimed in claim 1 or 2 wherein the inner pair of loudspeaker stations are positioned symmetrically between the outer pair of loudspeaker stations.

4. A system as claimed in claim 1, 2 or 3 having a multi-section filter arranged to divide each stereophonic signal into at least two subsignals each extendmg substantially only within a respective frequency range, the sub-signals being supplied to respective loudspeaker units at the associated inner and/or outer loudspeaker stations.

5. A system as claimed in claim 1, 2 or 3 wherein each loudspeaker station comprises a single loudspeaker unit.

6. A system as claimed in any preceding claim having means for reproducing as sound at an additional loudspeaker station positioned between the outer pair of stations a third signal representing sound related to or forming a art of an original sound source from which the stereophonic signals were derived.

7. A system as claimed in claim 6 wherein the additional loudspeaker station is located centrally between the outer pair of loudspeaker stations.

8. A system as claimed in claim 6 or 7 including a multi-section filter for dividing the third signal into at least two signals each extending substantially only within a respec

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. the signals supplied to the stations 1 and 2 can then be supplied directly also to the stations 3 and 4 respectively. The system of Figure 1 of course reproduces the lower frequency portion of each of the stereophonic signals at both the inner stations 3 and 4 as well as at both stations 1 and 2. Figure 2 shows a second sound reproduction system in accordance with the invention in which a source 15 provides stereo signals to respective spaced loudspeaker stations 11. 12. As in the system of Figure 1, these signals are passed through passive or active filters 16 and 17 respectively, so that the lower frequency range only is supplied to respective loudspeaker stations 13, 14 positioned generally centrally between the stations 11, 12. However, in Figure 2 a fifth loudspeaker station 18 is positioned between the loudspeaker stations 13, 14 and the source 15 supplied to this station 18 a third signal to be reproduced as sound by the station 18 alone. The third signal can be derived from the sound source that provided the two stereophonic signals, for example, from a soloist or group of soloists performing with an orchestra, the sound of which is mainly carried by the stereophonic signals. If so, there will normally be parts of the third signal present in each of the stereophonic signals and vice versa. Instead, the third signal may be from a separate source, for superimposition on the sound obtained from the stereophonic signals. In either event, the provision of the third channel through the loudspeaker station 18 permits the reproduction of the third signal to be controlled independently of the stereophonic signals; appropriate control means are provided at tie source or in association with the source 15 and/or at the loudspeaker stations or some of them. In the system of Figure 2, the source 15 will not normally be conventional, in as far as it has to produce three signals which however related are essentially different. The third signal can of course be multiplexed with one or other of the stereophonic signals, but can of course be derived from a special track on a magnetic tape. Although in Figure 2, the loudspeaker stations it, 14, 18 are shown as separate cabinets positioned side by side, the loudspeaker units of these stations can be housed in a single cabinet or the cabinets differently arranged for example so that the cabinet of station 18 overlies those of stations 13 and 14. Each of the loudspeaker stations mentioned so far can comprise at a minimum a single suitably mounted speaker unit. At least the loudspeaker stations 1, 2 and 11, 12 however, in order that they shall adequately reproduce sound over substantially the whole audio frequency range, preferably comprise a plurality of loudspeaker units to which the incoming respective stereophonic signal can be distributed through a crossover network. It is however preferred to eliminate the distortions inherent in the use of crossover networks by the use of a multi-channel system, by which each signal is divided into at least two sub-signals each extending substantially only within a respective frequency range, the sub-signals being supplied to respective loudspeaker units within the associated inner and/or outer loudspeaker stations.The third signal can be treated similarly, the loudspeaker station 18 having an appropriate plurality of separate loudspeaker units. Reference is made to Application 8 100 235, (Serial No. 1 604 767), divided from the present application. WHAT WE CLAIM IS:

1. A sound reproduction system comprising means for reproducing left and right hand stereophonic signals as sound over substantially the entire audio frequency range at respective ones of a pair of spaced apart outer loudspeaker stations, and means for reproducing as sound only the lower frequency portions of the signals at respective ones of a pair of loudspeaker stations.

tive frequency range, the divided signals being supplied to respective loudspeaker units at the additional loudspeaker station.

9. A sound reproduction system substantially as herein described with reference to Figure 1 of the accompanying drawing.

10. A method of reproducing stereophonic signals extending over substantially the entire audio frequency range as sound, the method comprising the steps of supplying substantially the entire signals to respective ones of a pair of spaced apart outer loudspeaker stations, and supplying the lower frequency part of the signals only to respective ones of a pair of inner loudspeaker stations located between the outer pair.

11. A method of reproducing as sound recorded electric signals substantially as herein described with reference to Figure 1 of the accompanying drawing.

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