The Sound Retrieval System (SRS) is a patented psychoacoustic  3D audio processing technology originally invented by Arnold Klayman in the early 1980s.  (The original SRS patents are US patents 4,866,774, 4,748,669, and 4,841,572, which expired in 2006 and 2008 depending on the patent.  Patents may apply in other countries. ) The SRS technology applies head-related transfer functions (HRTFs) to create an immersive 3D soundfield using only two speakers, widening the "sweet spot," creating a more spacious sense of ambience, and producing strong localization cues for discrete instruments within an audio mix.  SRS is not a Dolby matrix surround decoder but works with normal stereo recordings.

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