2 bookshelves for a center

Separating them farther does not eliminate the interference, it simply extends it down into lower frequencies (frequencies whose 1/2 wavelength is less than the distance between the drivers).

Your suggestion of using them one above and one below (both aimed at the listener) is a good one if one must use two. This would have the interference patterns confined mostly to the vertical plane giving the listeners in the seating plane a better soundfield and some ability to move around.

"Still, I think having a "BETTER center speaker" is usually going to be the better answer!" Ditto.

Kal

"Separating them farther does not eliminate the interference, it simply extends it down into lower frequencies (frequencies whose 1/2 wavelength is less than the distance between the drivers)." (kr4)

Yes, indeed. However, running the center channel as "small" or 80hz region should help allow one to keep the speakers a reasonable enough distance apart, that there shouldn't be a problem. I would think that affecting the upper bass/mid frequencies would be the critical range to not be "filtering" but I could be wrong here. (as bass is very important to remain intact, as much as possible, I understand)

I guess I should do the math, just to know that range if ever needed.
Lol - yes, better center sounds better to me too...

Do the math. Remember, there will be interference of all frequencies ABOVE the one whose 1/2 wavelength equals the separation. Therefore, a low cut is irrelevant.

Kal

Kr4, really? maybe my thinking is backwards. Because from what you're invering, if you place the speakers, say 100 feet appart, than ALL the frequencies are filtered between the speakers, and you'd be canceling out frequencies across the board - as you stood in front of one speaker, or closer in proximity, etc!! So, this can't be right, can it?
My understanding is that any frequencies, who's 1/2 wavelength distance between the two drivers playing the same mono info between them, was LESS than the 1/2 wave length distance, then you'd run into some phase cancellation issues in that case (so, for instance, basically the tweeters would only cancel each other in certain frequencies it covered if both tweeters were too close to each other, and you got off axis on one or both - like in a THX speaker arrangement - and your saying any mono info between two tweeters spread apart will comb, yes?).
Am I looking at this wrong? Because if that's the case, then what you're saying is that most ANY L/R speaker stereo setup, where you listen off-axis, would be filtering frequencies across a large portion of the frequency range!!!
(which should make the sound "horrible if you sat off axis)
Well I'll definitely do some research now, either way - lol