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How to get multichannel sound from a CD?

I was at a friend's place recently and heard him play CDs through his new Linar multichannel amp, which has the ability to direct part of the stereo signal to the back speakers. The effect was surprisingly good: spatiality and power increased, without any apparent damage to sound quality (as long as the rears were not too loud!).

This got me thinking: Rather than wait forever for the major labels to start releasing good quality multichannel recordings in SACD or DVD-A, why not explore ways to get extra spatiality out of my existing large CD collection?

So I'm looking to find out what options exist for doing this. I'm just gathering info at this point, so any tips you have are of interest--a bonus would be your comments on how good it sounds, but just hearing about an option is good too.

Note that I do care very much about sound quality issues such as timbre, tonality, musicality. The best options for converting CD to multichannel will do minimal/no damage to essential sound quality, but will add spatiality.

So far I know about the following:
-The Linar amps, and maybe other multichannel amps, that just direct the sound to the back
-the Meridian 861 processor has a mode for this. Super expensive, supposed to be good.
-the McCormack universal player has a mode also. Stereophile seemed to like it a bit less than the Meridian for this purpose, but it costs a lot less.
-I think DTS has a processing mode in some receivers which can do this (I'm not much of a home theater guy, no receiver in my system, so I'm sure many of you will know more than I about this).

Any others you guys know about?
calanctus

Showing 2 responses by eldartford

eldartford
4,262 posts
 
What we are talking about is "matrix multichannel". With most any surround decoding system, Dolby, DTS, etc. signal that is out of phase between the two channels goes to the rear speakers. This is very damatic if you play a Test rrecording that has material recorded inphase, and out-of-phase for phasing check purposes.

The effectiveness when playing music depends entirely on how the particular recording was mixed. Some stereo recordings that were never intended for multichannel playback are, by accident, dramatic. Most don't work very well. There is no way to tell except to try them.
eldartford
4,262 posts
 
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.
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