In a sound reproduction system of the type which enables the listener to distinguish sound from sources extending over 360.degree. of azimuth, compensation is provided for the asymmetry arising when four loudspeakers are located at the corners of a non-square rectangle. Compensation is also provided...http://www.google.de/patents/US3997725?utm_source=gb-gplus-sharePatent US3997725 - Multidirectional sound reproduction systems
