GB1604767A - Recording of sound - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO THE RECORDING OF SOUND (71) We, A.R.D. TECHNICAL ASSISTANCE AND ENGINEERING SERVICES INTERNATIONAL AN STALT, of P.O. Box No. 34.613, 9490 Vaduz, Liechtenstein, a body corporate organised under the laws of Liechtenstein, 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 method of recording sound, to a record medium produced by the method, and to a method and apparatus for reproducing sound from such a medium.

The invention accordingly provides a method of recording on a record medium sound from an extended first source and from a concentrated second source separate from the first source, the method comprising providing and recording on the medium two stereophonic signals only representing sound at least predominantly from the extended first source and a third, monophonic signal representing sound at least predominantly from the concentrated second source, each of the signals extending over substantially the entire audio frequency range.

The invention also provides a record medium produced by Quch a method, and a method of reproducing as sound the signals recorded on the medium, the latter method comprising reproducing the stereophonic recorded signals as sound at respective spaced apart first and second loudspeaker stations and reproducing the monophonic recorded signal as sound at a third loudspeaker station located between the first and second loudspeaker station.

The invention also provides a sound reproducing apparatus comprising a record medium means for deriving the recorded signals from the medium, first and second amplifying means for amplifying respective ones of the stereo phonic signals, means for supplying each amplified signal to a respective one of spaced apart first and second loudspeaker stations, means for amplifying the monophonic signal and means for supplying the amplified monophonic signal to a single third loudspeaker station located between the first and second loudspeaker stations.

The invention can therefore be embodied in a record medium, for example, a phonograph record or a magnetic tape, having recorded thereon two stereophonic signals, which are derived from an extended sound source for example an orchestra, and a third signal, derived from relatively concentrated source, typically a soloist. This technique is not however limited to sound sources comprising a soloist or an orchestra but can be employed for recording a solo singer accompanied by a pianoforte. In any event, the concentrated and extended sound sources can be reproduced in a relationship which is selectively adjustable during recording and reproduction.

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

In the system of Figure 1, two recorded sound signals steriophonically representing an extended sound source are reproduced as sound by means of four loudspeaker stations positioned as shown, with loudspeaker stations 11 and 12 spaced well apart, for example, with their centres two or three metres apart, and loudspeaker stations 13 and 14 grouped together at a position midway or approximately midway between stations 11 and 12. The steriophonic signals are supplied to the loudspeaker stations 11 and 12 from a source 15, which may be any appropriate source of such signals, for example, a phonographic source, a tape deck or a stereophonic radio receiver. The source 15 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 such a basic stereophonic arrangement, sound in the lower part of the audio frequency range only is reproduced in the central region between the loudspeaker stations 11 and 12, by means of the loudspeaker stations 13 and 14. The signals obtained from the source 15 will normally cover substantially the whole of the audio frequency range, and the "gap" effect resulting from the spacing of the stations 11 and 12 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, be- cause the lower frequency sounds have much less distinctly directional characteristics than sounds in the upper part of the frequency range. Accordingly, the stereophonic signals from the source 15 are supplied to the loudspeaker stations 13 and 14 through respective passive or active filters 16, 17 so that these two central loudspeaker stations reproduce substantially only signals below a predetermined frequency.

The limitation of the sound output of the loudspeaker station 13 and 14 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 11 and 12 can then be supplied directly also to the stations 13 and 14 respectively.

The system of Figure 1 of course reproduces the lower frequency portion of each of the stereophonic signals at both the inner stations 13 and 14 as well as at both stations 11 and 12.

Instead, the signals from the source 15 can be divided by suitable filter means into upper frequency parts which are supplied to the outer loudspeaker stations 11 and 12 only, and lower frequency parts, fed only to the stations 13 and 14. A fifth loudspeaker station 18 is positioned between the loudspeaker stations 13, 14, and the source 15 supplies to this station 18 a third signal to be reproduced as sound by the station 18 alone.

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 the source or in association with the source 15 and/ or at the loudspeaker stations or some of them.

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 1, the loudspeaker stations 13, 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 11 & 12 however, in order that they shall adequately reproduce sound over substantially the whole audio frequency range or the under part of it, preferably comprise a plurality of loudspeaker units to which the incoming respective stereophonic signal can be distributed through a cross-over network. It is however preferred to eliminate the distortions inherent in the use of cross-over networks by the use of multi-channel processing system. The sound reproduction system of figure 2 shows an example of this.

The system of figure 2 has a sound source 21 supplying stereophonic signals respectively to loudspeaker stations corresponding in function generally to that of the loudspeaker stations 11 and 12 of figure 1. However in figure 2, only the right hand station 22 of these two stations is shown. The figure 2 system also includes stations 23, 24 and 25 corresponding respectively in function generally to the stations 13, 14 and 18 of figure 1; the arrangement will be understood to be essentially symmetrical as with the arrangement of figure 1. To the loudspeaker station 25, the source 21 supplies a third signal in generally the same way as the source 15 supplied a third signal to the station 18.

In the system of figure 2, the outer station 22 and the corresponding outer station on the other side reproduce substantially only signals above a predetermined frequency, whilst the inner loudspeakers 23 and 24 reproduce substantially only signals below this frequency.

The division of the signal from the source 21 is effected in a multisection filter 26 which provides eight outlet lines carrying signals respectively in the frequency ranges above 12 k.Hz, 6 k.Hz - 12 k.Hz, 3 k.Hz - 6 k.Hz, 300 Hz - 3 k.Hz, 160 Hz - 300 Hz, 80 Hz - 160 Hz, 40 Hz - 80 Hz and 20 Hz - 40 Hz. The signals of lines 27-32 are supplied to respective loudspeaker units or groups of units all appropriately mounted, as within respective compartments, in the loudspeaker station 22. Signals on lines 33 and 34 are fed to respective loudspeaker units, or groups of units, similarly housed in compart ments of the loudspeaker station 24. The third signal supplied to the loudspeaker station 25 can be treated similarly, where the station is provided with a plurality of loudspeaker units.

It will be evident that the system described in connection with figure 2 can be modified in a variety of ways. For example each of the stereophonic signals can be supplied to a pair of multi-section filters located respectively at the stations 22, 24, for providing signals in the frequency ranges appropriate to the loud speaker units provided at those stations. The circuit can include compensation means to provide a fixed or variable amount of compensation for the characteristics of the loudspeaker units at the stations.The stereophonic signals may be divided by a multisection filter similar to the filter 26, to provide relative adjustment of the amplitude of the respective outputs at the station, after which the adjusted signals are recombined, for example into two signals, so that these can be fed respectively to the stations 22 and 24 for division at those stations by means of appropriate further multisection filters.

Reference is made to UK Application 22 690/78 (Serial No. 1,604,766) from which the present application was divided.

WHAT WE CLAIM IS: 1. A method of recording on a record medium sound from an extended first source and from a concentrated second source separate from the first source, the method comprising providing and recording on the medium two stereophonic signals only representing sound at least predominantly from the extended first source and a third, monophonic, signal representing sound at least predominantly from the concentrated second source, each of the signals extending over substantially the entire audio frequency range.

2. A method as claimed in claim 1 wherein the sound represented by the third signal is independent of the sound represented by the two stereophonic signals.

3. A method of recording sound substantially as herein described.

4. A record medium produced by the method of claim 1, 2 or 3.

5. A record medium as claimed in claim 4 in which the recorded monophonic signal is multiplexed with one of the recorded stereophonic signals.

6. A record medium substantially as herein described.

7. A method of reproducing as sound the signals recorded on a record medium as claimed in claim 4, 5 or 6 comprising reproducing the stereophonic recorded signals as sound at respective spaced apart first and second loudspeaker stations and reproducing the monophonic recorded signal as sound at a third loudspeaker station located between the first and second loudspeaker stations.

8. A method as claimed in claim 7 having the steps of dividing the stereophonic signals and/or the monophonic signal into at least two sub-signals each extending substantially only within a respective frequency range and reproducing each sub-signal as sound by means of a respective loudspeaker unit at the associated loudspeaker station.

9. A sound reproducing apparatus comprising a record medium as claimed in claims 4, 5 or 6, means for deriving the recorded signals from the medium, first and second amplifying means for amplifying respective ones of the stereophonic signals, means for supplying each amplified signal to a respective one of spaced apart first and second loudspeaker stations, means for amplifying the monophonic signal and means for supplying the amplified monophonic signal to a single third loudspeaker station located between the first and second loudspeaker stations.

10. An apparatus as claimed in claim 9 having multi-section filter means for dividing the stereophonic signals and/or the monophonic signal into at least two sub-signals each extending substantially only within a respective frequency range, and means for supplying each sub-signal to a respective loudspeaker unit at the associated loudspeaker station.

11. A sound reproducing apparatus substantially as hereinafter described with reference to Figure 2 of the accompanying drawing.

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

Claims (11)

**WARNING** start of CLMS field may overlap end of DESC **. speaker units provided at those stations. The circuit can include compensation means to provide a fixed or variable amount of compensation for the characteristics of the loudspeaker units at the stations. The stereophonic signals may be divided by a multisection filter similar to the filter 26, to provide relative adjustment of the amplitude of the respective outputs at the station, after which the adjusted signals are recombined, for example into two signals, so that these can be fed respectively to the stations 22 and 24 for division at those stations by means of appropriate further multisection filters. Reference is made to UK Application 22 690/78 (Serial No. 1,604,766) from which the present application was divided. WHAT WE CLAIM IS:

1. A method of recording on a record medium sound from an extended first source and from a concentrated second source separate from the first source, the method comprising providing and recording on the medium two stereophonic signals only representing sound at least predominantly from the extended first source and a third, monophonic, signal representing sound at least predominantly from the concentrated second source, each of the signals extending over substantially the entire audio frequency range.

2. A method as claimed in claim 1 wherein the sound represented by the third signal is independent of the sound represented by the two stereophonic signals.

3. A method of recording sound substantially as herein described.

4. A record medium produced by the method of claim 1, 2 or 3.

5. A record medium as claimed in claim 4 in which the recorded monophonic signal is multiplexed with one of the recorded stereophonic signals.

6. A record medium substantially as herein described.

7. A method of reproducing as sound the signals recorded on a record medium as claimed in claim 4, 5 or 6 comprising reproducing the stereophonic recorded signals as sound at respective spaced apart first and second loudspeaker stations and reproducing the monophonic recorded signal as sound at a third loudspeaker station located between the first and second loudspeaker stations.

8. A method as claimed in claim 7 having the steps of dividing the stereophonic signals and/or the monophonic signal into at least two sub-signals each extending substantially only within a respective frequency range and reproducing each sub-signal as sound by means of a respective loudspeaker unit at the associated loudspeaker station.

9. A sound reproducing apparatus comprising a record medium as claimed in claims 4, 5 or 6, means for deriving the recorded signals from the medium, first and second amplifying means for amplifying respective ones of the stereophonic signals, means for supplying each amplified signal to a respective one of spaced apart first and second loudspeaker stations, means for amplifying the monophonic signal and means for supplying the amplified monophonic signal to a single third loudspeaker station located between the first and second loudspeaker stations.

10. An apparatus as claimed in claim 9 having multi-section filter means for dividing the stereophonic signals and/or the monophonic signal into at least two sub-signals each extending substantially only within a respective frequency range, and means for supplying each sub-signal to a respective loudspeaker unit at the associated loudspeaker station.

11. A sound reproducing apparatus substantially as hereinafter described with reference to Figure 2 of the accompanying drawing.