Placement of centre channel

Sadly, both positions have problems, as you've noted. Placing the speaker on a shelf above the TV might be better. Having to look up because the TV is too high can cause a sore neck. Whichever you choose, the speaker should be tilted so that its tweeter points toward ear-height at the listening position.

Post some pircutures please. Meantime you may look at my setup (in my sig) where I have all 3 fronts (LCR) above the TV. All are tilted and nudged off the shelf by about an inch. Tilting them is important so as to be on-axis with the seated listening position coz speakers have their widest frequency response and highest SPL (Sound Pressue Level) when on-axis. There's another factor called toe-in or angling. This is mostly important for the Front L&R speakers. Whether to do it or not should always depend on the maker's suggestion. Look up the manual of your speakers to see what they recommend. In my case Dali does not recommend angling, so as you can see my Front L&R speakers are parallel with the front wall. The Center speakers is also tilted facing the MLP (Main Listening Position) at seated ear height.
Edited by mogorf - 12/6/12 at 1:58pm

Any way for you to get the AV combo out of the corner and set it up against the adjacent front wall?

Corner placement is not a bad thing acoustically.

Yup. I've used firing the audio across the room diagonally to obtain a more favorable acoustic environment in the past.

I don't think it's really necessary to suggest that one of the above posts is, uh, technically incorrect, besides being nearly incomprehensible and non responsive.

OP if you can find a non-destructivem inexpensive way to try both, it could be worthwhile. My center is below my TV, but the TV is not TOO high. Some have stated, IIRC,that they found above the video to provide a more seamless experience. But tilting the speakers, in either situation, can be important. Because the wavelengths are so short at typical tweeter crossover frequencies, a relatively few degrees off axis can significantly change the frequency response in that crossover region, causing frequencies that were supposed to add together from both tweeter and woofer/midrange to subtract from each other because they're not in the correct relative phase at the listening position.

Assuming the CC's big enough, it's easier to put the TV on top of a CC so why not try that first? You may find the bass is a little heavy as the stand and screen act like walls to reinforce low frequencies. You'd hear a lesser effect if mounted above, but one room correction SW can deal with.

Conversely, if the CC's too small to fit under the TV... you need a larger CC! Just my opinion there, but a valid one... CC's should not be small speakers!

HAve fun,
Frank

But if the CC is acting as a stand, its top surface has to be horizontal, so its tweeter can't be tilted up to point toward the ears of the viewer.

With some speakers that'll be OK, but in others, there'll be a significant loss in the audibility of high frequencies.

Agree.

Those with a projector and a screen can easily solve the problem by installing acoustically transparent screens, so the placement of their Center speaker can be right behind the screen for best dialog intelligibility in harmony with the picture itself.

But us, regular mortals, with flat screen TVs have to take careful measures when it comes to Center speaker placement. The two choices we have are: above or below the screen.

Below needs tilt up, above needs tilt down, all this, of course, to be done in order to face seated ear height for improved dialog intelligibility.

Owing to the fact that our human ears are most sensitive for vertical directionality of sounds at an angle from our eyes down to the ground, and loose this sensitivity when looking/facing upward, the placement of the Center above the screen is more advisable than below, coz in this case picture and sound integration as regards directionality will be smoother. This sensitivity issue derives from evolution when the cavemen had to have sensitive ears to spot those things that wanted to eat them, usually coming vis-a-vis on the ground. Nothing changed in our hearing mechanism for this matter ever since.

In some TV viewing rooms, where the seating is all centered and some distance from the speakers, another option is to eliminate the center speaker entirely. Sometimes such a "phantom center speaker" can be quite effective. If seating is scattered around the room, though, a center speaker is needed to "anchor" the sound, especially dialog, at the TV. Otherwise it'll seem to come from the speaker closest to the seating.