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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

Showing 3 responses by almarg

almarg's avatar
almarg
9,670 posts
 
Just guessing, but maybe he is referring to phase differences of reflections off of the wall behind the tv set. The path length from one center speaker (say the top one) to that wall and back to that speaker is different than the path length from the bottom center speaker to that wall and then to the top center speaker. Perhaps that could result in some degree of frequency response irregularity.

Regards,
-- Al
almarg's avatar
almarg
9,670 posts
 
Just guessing, but maybe he is referring to phase differences of reflections off of the wall behind the tv set. The path length from one center speaker (say the top one) to that wall and back to that speaker is different than the path length from the the bottom center speaker to that wall and then to the top center speaker. Perhaps that could result in some degree of frequency response irregularity.

Regards,
-- Al
almarg's avatar
almarg
9,670 posts
 
Good thoughts in the preceding posts, except that I would respectfully disagree with this statement:

I don't think that putting mono speakers above and below the TV will make it sound like the sound is coming from the TV. The sound will still come from the speakers above and below the TV. That's what mono is and does. You need stereo, not mono, to do what you want to do.

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. You can easily verify that by playing a mono recording through your system; the result will be a focused image centered between the speakers, assuming the speakers and amplifier are connected in phase, and that there are no significant channel imbalances.

Although in BOTH cases I believe that Hhiggins is correct that if the speakers are too close together, comb filtering effects can occur at frequencies which are high enough to make the effects audibly significant.

Regards,
-- Al
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