Calanctus...All the matrix multichannel schemes involved out-of-phase signal being emphasized in the rear channels, and deemphasized in the fronts, with the exact ratios varying somewhat between systems. The SQ LP system also involved some plus and minus 90 degree phase shifting which allowed a SQ decoder to provide better separation. All systems work best when the recorded material was encoded for the particular kind of decoder used for playback, but there is enough commonality between schemes that decent results may be achieved with differing schemes.
DSP (Digital Signal Processing) uses delay and recirculating signal to create an artificial echo that simulates hall acoustics. Usually the playback system includes a way to select different amounts of this echo effect, so as to simulate large and small halls. Outboard equipment for DSP were the first consumer applications of digital technology to audio, and replaced metal spring devices that were previously used. Many present-day surround sound processors include DSP...why not, because it is easy to implement since the signal is already in digital format. My Rotel SS processor has DSP, but I rarely use it. If I want to do multichannel playback of two channel material I usually use Dolby Prologic II. PLII has a useful three channel mode that gets me a signal for the center front speaker without any rears. DTS sends less to the rears.
DSP (Digital Signal Processing) uses delay and recirculating signal to create an artificial echo that simulates hall acoustics. Usually the playback system includes a way to select different amounts of this echo effect, so as to simulate large and small halls. Outboard equipment for DSP were the first consumer applications of digital technology to audio, and replaced metal spring devices that were previously used. Many present-day surround sound processors include DSP...why not, because it is easy to implement since the signal is already in digital format. My Rotel SS processor has DSP, but I rarely use it. If I want to do multichannel playback of two channel material I usually use Dolby Prologic II. PLII has a useful three channel mode that gets me a signal for the center front speaker without any rears. DTS sends less to the rears.