Do surround modes alter Left/Right signals for 2ch sources?

If he used the Lexicon mode 'Music Surround' on his DC-2 it wouldn't touch the L/R channels either.

"If I configure my processor (in my case an 861v4) to not use a center channel for two channel music, do the better surround modes (say Trifield, PL2x Music, and/or MusicLogic)"

Depends upon the mode. PL2X will steer surround material out of L/R and I think Meridian's 'MusicLogic' would as well. With Trifield I think the surround channel is basically a passive matrix so it might not change the front channel content.

Easy enough to try this on your Meridian. Configure it for no center but with surround channels and turn off surrounds amps. Compare the various modes against Stereo and see if you hear a difference other then possible level changes. Also use something like the in phase/out of phase test tracks on many discs to listen to this.

Shawn

I believe classic Trifield alters the levels of the front channels to maintain constant sound energy. There may be some filtering, but definitely no steering.

You can read more about Linkwitz's setup here:

http://www.linkwitzlab.com/surround_system.htm

"2 - Refinement of ambience recovery" talks about this setup. I'm kind of surprised that he did this, but maybe Music Surround isn't explained well enough in the manual?

--Andre

Andre,

"but maybe Music Surround isn't explained well enough in the manual?"

Maybe, the DC-2 manual itself doesn't go into much detail but it is spelled out pretty clearly in the Theory and Design book.


In the Music Surround effect, the front left and right outputs are attenuated
by the volume and balance controls, but are otherwise unaltered by the
processor. This absence of main front steering is ideal for playing stereo
classical music, where the original stereo signals are reproduced from the
front speakers with absolutely no alterations. The Music Surround effect
really shines on this material — the center speaker adds a little stability to
the front image without being at all obvious, while the side and rear
speakers add a tremendous amount of ambience.

Shawn

It depends on the particular mode, but most do yes. I believe DTS Neo6 did not, though Roger Dressler at Dolby informed me that there were multiple versions of neo 6 and that some did and some didn't. I don't know about proprietary modes from Meridian and Lexicon and the like, you'd have to consult their literature to know what they're doing.

However, I would offer that if you want to leave the main channels unchanged, I would just listen in stereo. Because if you want to extract directional info and the like for ambiance, you want to remove that from the mains and place that elsewhere in the room, not just duplicate it other places redundantly. So while I understand the instinct to leave the main channels undisturbed, it's not necessarily going to make things better or more accurate. However, I am myself biased towards leaving stereo sources in stereo, so others who appreciate using surround modes or adding center channels or the like for stereo sources might have a different perspective.

my .02