GB2347600A

GB2347600A - Hi-Fi sound reproduction system

Info

Publication number: GB2347600A
Application number: GB9904996A
Authority: GB
Inventors: David Ernest Hendren
Original assignee: Individual
Current assignee: Individual
Priority date: 1999-03-04
Filing date: 1999-03-04
Publication date: 2000-09-06
Also published as: GB9904996D0

Abstract

An audio enhancement device for providing a more accurate imaging hi-fi system includes means for correction of frequency response to compensate for left to right ear time delay inter-aural distortion, a dividing network for producing additional left and right channel signals and supplying these via a control module (figure 1 not shown) to control intensity and amplification to a predetermined array of loudspeakers. The arrangement may be adjusted for the specific acoustic qualities of a particular room by independently adjusting the intensity of the various channels to provide a more accurate imaging hi-fi system i.e. not affected by the listener's position. The arrangement shown includes circuits A, B, C for producing various combinations of left, right channels which are filtered and applied to dividing networks to obtain additional left, right channel signals in addition to a centre channel C. Surround left, right channel signals may be applied in addition to the following module.

Description

HI-FI SOUND REPRODUCTION SYSTEM The present invention relates to a hi-fi sound reproduction system which seeks to provide a more accurate imaging high fidelity system for audio sound reproduction which will not be affected by the listener's position.

Attempts have been made in the past to improve the quality of sound reproduction by electronic means to improve (stereo) quality. An article entitled"Improve your image"by Richard Brice in Electronics World, October 1998, Vol. 104, No. 1750, pages 830-836 discusses the problem and puts forward some simple proposals, including a modified microphone technique for producing the original recording. However, relying upon correction applied at the microphone is effective only in respect of future recordings and does not provide any benefit for existing recordings. As such, it is preferable to perform such corrections when reproducing the sound, rather than when producing the recording.

According to the present invention there is provided an interaural phase and intensity correction system for enabling variable adjustment of parameters for a plurality of loudspeakers, comprising: input means for receiving left and right channel signals and combining such in a variety of combinations to provide output signals representing left, centre and right channels; respective filter means for receiving said left, right and centre channels, the centre channel being output unmodified from its respective filter; respective dividing network modules for receiving the filtered left and right channel signals, which modules each provide an additional left and right signal for output together with said unmodified centre channel signal.

Preferably, the output signals are input to a control module providing individually variable intensity outputs for a plurality of loudspeakers.

The control module preferably provides for wireless remote switching, pre-amplification and remote intensity/volume control for the various channels and a master volume control.

The signals may additionally include surround signals for surround sound type systems, which front signals are filtered then are fed directly into the control module with rear signals and then to amplifiers and to loudspeakers.

The present invention will be described further with reference to the accompanying drawings in which: Figure 1 illustrates a sound reproduction system of the present invention; Figure 1A illustrates in more detail the arrangement of module A of Figure 1; and Figure 2 illustrates the positioning of the loudspeakers within a room when used with the system of the present invention.

Referring firstly to Figure 1, the left and right signals (L, R) of a stereo signal are input into module A and where a centre signal is available from, for example a surround sound type system or the like, such may additionally be input.

Further rear surround sound signals (SR and SL) may also be provided, although such are not subject to processing by module A.

The respective signals are each applied to differential and summation amplifier modules A, B and C of module A (see Figure 1A), differential amplifier A producing an output representing left-right (L-R), whilst differential amplifier B provides an output which is the sum of the left and right channels (L+R) and differential amplifier C provides an output which is the difference right-left (R-L). The output of such differential amplifiers are applied to respective active filters. The outputs of the filters associated with amplifiers A and C are then output to respective dividing network modules, whilst the output of the filter associated with summation amplifier B is output directly. The dividing network modules respectively produce an outside left and an inside left output signal and an outside right and an inside right signal.

The two left signals blend together with the left part of the centre signal to produce on blending of the right signals the acoustic parameters on reproduction.

These five outputs are then input to module B (Figure 1) into which, if available, the surround signals SL and SR are also input. As mentioned above, module B provides for function switching pre-amplification and intensity/volume control for the channels as well as a master volume control for adjusting the listening level overall and provides outputs to the loudspeakers. If desired, the circuit may be duplicated for rear surround applications rather than utilising the normal surround signals SL and SR.

Additionally, provision can be made for the addition of"sub- woofer"low frequency loudspeakers with or without correction.

The arrangement of the present invention enables adjustment of intensity and phase which may be an analogue or surround digital/analogue signal. The phase signal is a fixed signal 6db per octave low pass filter signal which is flat from 2khz to 20khz. All channels have provision for some more differential processing and all five channels are required to be adjusted in intensity independently to enable a precise volume level to be provided to each of five loudspeakers by means of module B, which additionally includes the master volume control, as referred to above. This provides volume adjustment without altering intensity correction settings.

The system loudspeakers, for optimum performance, should have the following characteristics and may be arranged as set out in Figure 2. The centre loudspeaker is a narrow dispersion speaker, whilst the left and right inner and outer speakers are wide dispersion. These are the only parameters required, all other loudspeaker parameters being unaffected by this system.

The two left and right pairs of speakers, by varying driver axis, independently provide further acoustic correction to allow for different locations.

The frequency response in the lower frequencies is corrected by 6db's per octave to compensate for left to right ear time delay inter aural distortion together with inter-aural intensity distortion, which is the image blurring anomaly present in all sound reproduction systems that utilise loudspeakers. The system and multiple speaker arrangement disclosed provides an image which is stable, independent of the listening position of a listener within the room.

The centre channel option in Figure 1 also provides compatibility with home cinema and surround sound type systems.

The system of the present invention may be provided as a stand-alone unit or may be incorporated in the preamplification circuits of a preamplifier surround sound processor, a studio effects processor or a mixing desk. It may be utilised with any sound reproducing system which at present utilises stereophonic or multichannel sound, including recording studios, film and audio, domestic use TV, concert halls, film theatres or even military applications, i. e., any application where it is deemed desirable to reproduce an exact replica of the original sound recorded image or real-time image in the forward plane or surround sound through loudspeakers.

Claims

CLAIMS 1. An inter-aural phase and intensity correction system for enabling variable adjustment of parameters for a plurality of loudspeakers, comprising: input means for receiving left and right channel signals and combining such in a variety of combinations to provide output signals representing left, centre and right channels; respective filter means for receiving said left, right and centre channels, the centre channel being output unmodified from its respective filter; respective dividing network modules for receiving the filtered left and right channel signals, which modules each provide an additional left and right signal for output together with said unmodified centre channel signal.
2. A system as claimed in claim 1 in which said left and right channel signals and said centre channel signal are provided as inputs to a control module for providing individually variable intensity outputs for a plurality of loudspeakers.
3. A system as claimed in claim 2, in which said control module provides for wireless remote switching, preamplification and remote intensity/volume control for the various channels and a master volume control.
4. A system as claimed in any preceding claim in which surround signals for surround sound type systems are additionally provided to supplement said left, right and centre channel signals.
5. A system as claimed in claim 2, in which additional surround signals for surround sound type signals are provided, in which front signals are filtered then fed into said control module together with rear signals, and then fed to amplifiers and suitable loudspeakers.
6. An inter-aural phase and intensity correction system as claimed in any preceding claim and substantially as hereinbefore described with reference to the accompanying drawings.