Doug, you're really giving me a test here, but that's okay, I enjoy it. Okay, let's get into it:

1a&b) Yes, that's what I meant. I'm not claiming that I know that to be what Lexicon, et al, and their engineers had in mind with the Logic-7 decoding, just that it seems 'logical' to me. I do remember reading it somewhere, though.

By the way, in any case, when I mention side-positioned speakers, I'm referring to a position directly to the sides, not to the rear even a little bit.

If I were keeping my surrounds to the rear, I'd want a side speaker to fill in the 'gap', the way a center fills in for a pair of fronts to reinforce the 'sweet spot' for anybody off-center. In the exact center seating position, there is, theoretically, no difference between having and not having a center speaker (caveat: assuming proper recording, mixing, maintaining relative phase, high-quality and proper setup of the playback system, etc.)

Side note: When stereo began, there were THREE speakers, not two; the usual full-range two- or three-way unit, and a pair of satellites. (I'm not sure how the sound was steered, whether discrete or encoded, etc.) You should be able to understand the need for maintaining phase relationships, even though you can't form a 'phantom center' using one ear.

2) I don't know, you'd have to ask Lexicon. However, properly mixed and encoded surround sound should be able to approximate it. This is another reason I'd rather place the surrounds to the sides, even if there is no separate rear speaker. Plus, if you have a room that is wider than it is deep, the side position is a perfectly legitimate place for the surrounds.

3) My guess would be a 'spatializer' circuit of some sort. What these do is exaggerate the steering of the stereo difference, so sounds panned or located left sound farther left, etc. You could certainly try placing these front-effects speaker to the side.

4) Again, with any speakers to the rear of the main seating position, the sides should be directly to the side, not the back corners (not the best place for a speaker, anyway; too many early reflections). Also, all of my speakers, while not 'direct-radiating, are bi-polar, not di-polar, so they are closer to directional than not. The difference between the two is merely electrical, not physical; it depends on whether the drivers are wired + to + and - to - , or + to - and - to + .

For an explanation of the various speaker types, see: [Link: remotecentral.com]

About 'tri-polar': I haven't read anything about it, but I would guess it refers to a speaker with drivers on three sides. Still, as in the di-vs-bi wiring, the two (or two sets of) outer drivers could be wired bi-polar (in phase) or di-polar (out of phase).

However, the third, center-mounted driver must be wired in one direction or the other, and since there is no 'third phase', there really is no such thing as a 'tri-polar' speaker. Either all three faces are in phase (direct, bi-polar, or 'mono' all apply), the two outer in (bi-polar) and the center out (di-polar), or one face and the center in phase and the other out (di-polar).

Larry
www.fineelectricco.com