Apparatus for reproducing sound having an expanded acoustic image is used in a stereophonic sound reproduction system having a left channel output and a right channel output, which need not be binaural. A right main speaker and a left main speaker are disposed at right and left main speaker locations,...http://www.google.de/patents/US4497064?utm_source=gb-gplus-sharePatent US4497064 - Method and apparatus for reproducing sound having an expanded acoustic image
