Two mono center TV speakers out of phase?


I would like to use two mono center speakers with one over, and one under the TV to make the sound image appear to come from the TV, not above or below it. My home theater dealer said that he has talked to experts on the subject who told him not to do that because the sound will be out of phase. To me that makes no sense at all, because the mono signal to both speakers is the same, the two speakers are the same, and the two amps are the same. I would much rather hear the sound coming from the center of the TV, but what would cause the sound to be out of phase, or what other problem would this setup cause? This mono center channel is created from the left and right signals and is not a separate third center channel.
redwoodgarden
"There is no difference between a pair of stereo signals with identical left and right content (or in this case, top and bottom), and a mono signal fed to two identically placed speakers."

This is correct. A stereo signal with identical content left and right is, essentially, a mono signal. And of course, you should get a centre image if everything is set up properly as you would with a stereo pair. Therefore, upon reflection of my earlier comment, I would say that Almarg is correct about the imaging issue. However, proper distancing so that the two mono signals are not interfering with one another remains an issue to watch (or rather, listen) for.
Thanks for your comments. I still don't see why two mono speakers equal distant to the sweet spot using two identical amps will cause a problem. I'm using a 52 inch TV screen so I don't think that distance between the speakers should play a role. Perhaps connecting the two speakers to the same amp in series may have this negative effect, but I'm just guessing. I wouldn't do that anyway. I'll take Cyclonicman's suggestion and just do it.