Abstract: An audio enhancement system and method for use receives a group of multi-channel audio signals and provides a simulated surround sound environment through playback of only two output signals. The multi-channel audio signals comprise a pair of front signals intended for playback from a forward sound stage and a pair of rear signals intended for playback from a rear sound stage. The front and rear signals are modified in pairs by separating an ambient component of each pair of signals from a direct component and processing at least some of the components with a head-related transfer function. Processing of the individual audio signal components is determined by an intended playback position of the corresponding original audio signals. The individual audio signal components are then selectively combined with the original audio signals to form two enhanced output signals for generating a surround sound experience upon playback.

Abstract: A stereo enhancement system processes the difference signal component generated from a pair of left and right input signals to create a broadened stereo image reproduced through a pair of speakers or through a surround sound system. Processing of the difference signal component occurs through equalization characterized by amplification of the low and high range of auditory frequencies. The processed difference signal is combined with a sum signal, generated from the left and right input signals, and the original left and right input signals to create enhanced left and right output signals.

Abstract: An acoustic correction apparatus processes a pair of left and right input signals to compensate for spatial distortion as a function of frequency when said input signals are reproduced through speakers in a sound system. The sound-energy of the left and right input signals is separated and corrected in a first low-frequency range and a second high-frequency range. The resultant signals are recombined to create image-corrected audio signals having a desired sound-pressure response when reproduced by the speakers in the sound system. The desired sound-pressure response creates an apparent sound image location with respect to a listener. The image-corrected signals may then be spatially-enhanced to broaden the apparent sound image.

Abstract: Spatially enhanced sound is produced by vertically radiating a first sound from a left speaker by a first transducer. The first sound includes a sum component and a left difference component. A left difference sound is horizontally radiated from the left speaker by a second transducer. The left difference sound from the first transducer and the left component sound from the second transducer acoustically combine. A second sound is vertically radiated from a right speaker by a third transducer. The second sound includes a sum component and a right difference component. A right difference sound is horizontally radiated from the right speaker by a fourth transducer. The right difference sound from the third transducer and the right component sound from the fourth transducer acoustically combine and the sum component from the right speaker and the sum component from the left speaker acoustically combine.

Abstract: A stereo enhancement system processes the difference signal component generated from a pair of left and right input signals to create a broadened stereo image reproduced through a pair of speakers or through a surround sound system. Processing of the difference signal component occurs through equalization characterized by amplification of the low and high range of auditory frequencies. The processed difference signal is combined with a sum signal, generated from the left and right input signals, and the original left and right input signals to create enhanced left and right output signals.

Abstract: A loudspeaker (34,134) excites a quarter wave resonant air column that is folded forward on itself. The column is closed at one end and has an output port located at the other. The output port (20,120) is in line with the speaker so that the one speaker can excite air both at the output port and at the closed end of the resonant column. At resonance, the column loads the speaker, and the speaker regeneratively drives the column output. At other frequencies output from the port is partially from vibration of the air column and partially from the speaker. At resonance the direct speaker output regeneratively reinforces and combines with the output of the resonant column, which has a length of one-quarter of the wavelength of sound propagated in air at the resonant frequency.

Abstract: In a stereo system having sum and difference signals that are processed for stereo image enhancement, apparent directivity of the stereo sound is increased by the use of servo systems (40,44) for the left and right processed difference signals (L-R).sub.p, (R-L).sub.p. Each of the left and right servos (40,44) responds to the respective left or right stereo input signal (L.sub.in, R.sub.in) and amplifies increases in the respective left or right processed difference signals. The amount of amplification is controlled by feeding back the amplified or directivity enhanced difference signal (L-R).sub.pe, (R-L).sub.pe, first comparing it with the processed difference signal (L-R).sub.p, (R-L).sub.p before directivity enhancement, and then combining it with the input signal (L.sub.in, R.sub.in) in a preselected ratio so as to control the amount of amplification of the processed difference signal that is provided for directivity enhancement.

Abstract: A stereo image enhancement system, in which difference signal components in relatively quieter difference signal frequency bands are boosted to provide an improved stereo image, is provided with a stereo input that is synthetically derived from monaural signal (L+R). Simulated sum (L+R).sub.s and simulated difference (L-R).sub.s signals are provided from a monaural input (L+R) by sending the input through a phase shifter and splitter (12) that provides 0.degree. and 90.degree. outputs with a constant 90.degree. phase separation between the two at all audio frequencies. The leading one of the two output signals from the phase shifter is employed as a simulated sum signal, and the other as a simulated difference signal. The simulated difference signal has different frequency components, each delayed by different amounts relative to corresponding components of like frequency of the simulated sum signal.

Abstract: A wide dispersion baffle for a vertically oriented loudspeaker includes a first semi-conical reflective section that is concave toward the speaker and has a semicircular rim positioned at the periphery of the speaker. It extends at an angle of about 45.degree. to the radiation axis of the speaker to its apex on the speaker axis. A second semi-conical reflective section is convex toward the speaker and extends from the apex of the first semiconical section at substantially the same 45.degree. angle with respect to the speaker radiation axis. Sound emanating from the vertically directed speaker is reflected by both the concave and convex semi-conical reflector sections in a pattern centered about a substantially horizontal plane, but the sound is reflected through widely diverging angles in such horizontal plane. Baffle arrangements can provide horizonal dispersion patterns of any angular width between about 180.degree. and 360.degree..

Abstract: Direct field sound, represented by the sum of left and right stereo input signals, is projected in a narrow dispersion pattern from a front radiating speaker 28,32 and reverberant field sounds, represented by difference between left and right stereo input signals, is projected from speakers 26,30 having a wide dispersion pattern. Direct field and reverberant field sounds are acoustically combined in space to create an improved representation of stereo sound.

Abstract: A stereo enhancement system (300) is disclosed which provides an enhanced wider stereo image and a wider listening area, and further provides perspective correction for achieving correct stereo sound perspective with speakers at different locations and with headphones. The stereo enhancement system includes a stereo image enhancement system (100, 10, 110) which includes circuitry (11, 13, 111, 113) for generating sum and difference signals based on left and right stereo signals, circuitry (17, 18, 19, 22, 30, 115, 125, 129, 40) for selectively altering the relative amplitudes of the difference signal components, circuitry (17, 21, 30, 117, 127, 40) for selectively altering the relative amplitudes of the sum signal components, and circuitry (23, 25, 27, 119, 121, 123) for combining the processed sum and difference signals with the original left and right stereo signals to produce enhanced left and right stereo signals.

Abstract: A loudspeaker horn has a conical section adapted to receive the driver assembly of a speaker system at the small cone end. An exponential section secured to the large cone end, concentrically with the cone longitudinal axis, flares outwardly to terminate in a square cross-section horn mouth. A raised lip secured around the periphery of the horn mouth diffracts sound symmetrically through a dispersion angle of about 120.degree. with a drop of about six decibels or less.