Abstract: A signal processor for a sound reproduction system which is arranged to perform processing of a sound recording so as to provide input signals for an array of distributed loudspeakers, such that the sound field generated by the loudspeakers results in cross-talk cancellation in respect of multiple listener positions at substantially all frequencies reproduced by the loudspeakers, and wherein the sound field so generated is an approximation of a sound field produced by an Optimal Source Distribution, OSD.

Abstract: A sound reproduction system includes an electro-acoustic transducer and a transducer driver for driving the electro-acoustic transducer. The transducer drive includes a filter which is configured to reproduce at a listener's location an approximation to the local sound field that would be present at the listener's ears in recording space, taking into account the characteristics and intended position of the electro-acoustic transducer relative to the listener's ears. The electro-acoustic transducer includes a first sound emitter which provides an intermediate sound emission channel, and second and third sound emitters providing respective left and right sound emission channels. The first sound emitter is located intermediate of second and third sound emitters. Higher frequencies from at least one of the second and third sound emitters are transmitted closer to the first sound emitter while lower frequencies are transmitted away from the first sound emitter.

Abstract: A sound reproduction system includes an electro-acoustic transducer and a transducer driver for driving the electro-acoustic transducer. The transducer drive includes a filter which is configured to reproduce at a listener's location an approximation to the local sound field that would be present at the listener's ears in recording space, taking into account the characteristics and intended position of the electro-acoustic transducer relative to the listener's ears. The electro-acoustic transducer includes a first sound emitter which provides an intermediate sound emission channel, and second and third sound emitters providing respective left and right sound emission channels. The first sound emitter is located intermediate of second and third sound emitters. Higher frequencies from at least one of the second and third sound emitters are transmitted closer to the first sound emitter while lower frequencies are transmitted away from the first sound emitter.

Abstract: Sound recordings are played through a closely-spaced pair of loudspeakers with a predetermined listener position having an included angle of between 6° and 20°, and filter means being employed in creating said sound recordings, the filter means having characteristics such that when the sound recordings are played, the need to provide a virtual imaging filter means at the inputs to the loudspeakers to create virtual sound sources is avoided, the sound recording being such that when played through the loudspeakers a phase difference between vibrations of the two loudspeakers results where the phase difference varies with frequency from low frequencies where the vibrations are substantially out of phase to high frequencies where the vibrations are in phase, the lowest frequency at which the vibrations are in phase being determined approximately by a ringing frequency, f0.

Abstract: A sound reproduction system has pairs of sound emitters that subtend different angles ?, the span angle, at the listener position. The pairs of sound emitters are arranged to be excited by different frequency bands of the signal output from an inverse filter means (Hh, Hl). The operational span-frequency range of the pairs of sound emitters is determined by an equation (I) where the transducer span ? is the angle subtended at the listener by a pair of transducers, where O<n<2. c0: is the speed of sound, and ?r: is the equivalent distance between the ears. The sound emitters may be discrete speaker units, the different pairs of units being positioned at different span angles, or they be constituted by area portions of an extended transducer (FIG. 10). When discrete speaker units are employed a cross-over filter (FIG. 28) is used to provide drive signals in the different frequency bands to the different speaker pairs.

Abstract: Sound recordings are played through a closely-spaced pair of loudspeakers with a predetermined listener position having an included angle of between 6° and 20°, and filter means being employed in creating said sound recordings, the filter means having characteristics such that when the sound recordings are played, the need to provide a virtual imaging filter means at the inputs to the loudspeakers to create virtual sound sources is avoided, the sound recording being such that when played through the loudspeakers a phase difference between vibrations of the two loudspeakers results where the phase difference varies with frequency from low frequencies where the vibrations are substantially out of phase to high frequencies where the vibrations are in phase, the lowest frequency at which the vibrations are in phase being determined approximately by a ringing frequency, f0.

Abstract: A method of recording sound for reproduction by a plurality of loudspeakers, or for processing sound for reproduction by a plurality of loudspeakers, is described in which some of the reproduced sound appears to a listener to emmanate from a virtual source which is spaced from the loudspeakers. A filter means (H) is used either in creating the recording, or in processing the recorded signals for supply to loudspeakers, the filter means (H) being created in a filter design step in which: a) a technique is employed to minimise error between the signals (w) reproduced at the intended position of a listener on playing the recording through the loudspeakers, and desired signals (d) at the intended position, wherein: b) said desired signals (d) to be produced at the listener are defined by signals (or an estimate of the signals) that would be produced at the ears of (or in the region of) the listener in said intended position by a source at the desired position of the virtual source.

Abstract: A sound reproduction system comprises a plurality of loudspeakers (S1, S2) spaced from a listener at a location (M1, M2), and a loudspeaker drive means (H) for driving the loudspeakers (S1, S2) in response to a plurality of channels of a sound recording (x) of the type being suitable for playing normally through a plurality of reference speakers that are optimally positioned at locations that are displaced from the actual positions of the loudspeakers (S1, S2). The loudspeaker drive includes a filter (H), having a filter characteristic selected by minimising the difference between a desired sound field that would be created by playing the unfiltered sound recording (x) through the reference speakers and sound field reproduced at the listener location (M1, M2) by playing the recording through the speakers (S1, S2).

Abstract: A method of recording sound for reproduction by a plurality of loudspeakers, or for processing sound for reproduction by a plurality of loudspeakers, is described in which some of the reproduced sound appears to a listener to emmanate from a virtual source which is spaced from the loudspeakers. A filter means (H) is used either in creating the recording, or in processing the recorded signals for supply to loudspeakers, the filter means (H) being created in a filter design step in which: a) a technique is employed to minimise error between the signals (w) reproduced at the intended position of a listener on playing the recording through the loudspeakers, and desired signals (d) at the intended position, wherein: b) said desired signals (d) to be produced at the listener are defined by signals (or an estimate of the signals) that would be produced at the ears of (or in the region of) the listener in said intended position by an source at the desired position of the virtual source.

Abstract: A stereophonic sound reproduction system is aimed at synthesizing at a multiplicity of points (L) in the listening space. An auditory effect obtaining at corresponding points (K) in the recording space, to compensate for crosstalk (C.sub.21, C.sub.12) between the loudspeakers, the acoustic response of the listening space, and imperfections in the frequency response of the speaker channels. Each speaker channel incorporates a digital filter (H) with the characteristics of which are adjusted in response to measurements of the reproduced field. The digital filters are provided by an inverse filter matrix (H) of which the matrix elements (H.sub.ij) are determined by a least squares technique, applied so as to minimize the sum of the squared errors resulting from the difference between the actual system impulse response and a desired impulse response. A full bandwidth signal is transmitted by a bypass route for combination with the output signal (9) from the filter, the bypass route including a delay means (F).