This article is from the Ambisonic Surround Sound FAQ, by Martin Leese with numerous contributions by others.
Domestic Ambisonic decoders feature a Super Stereo button for decoding
stereo sources. This uses the rear part of the sound field to
reinforce the location of sounds in front of the listener. In
addition, any ambience present in the source will be directed all
around the listener, although the effectiveness of this depends
greatly on the recording technique that was used. The Super Stereo
mode also includes a stereo width control which allows the stereo
image to be compressed to mono-like or expanded into a horseshoe
around the listener.
 
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