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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
stanwal's avatar
stanwal
3,147 posts
 
I don't understand this either. I am not a HT man, I have one but it is a stereo one, but how can 2 mono speakers be out of phase with each other? I don't understand how they can be out of phase with the stereo signal either but as I said I am not a HT expert. Three channel sound was current in the early 60s when I got into audio and I had a Fisher amp that had a separate mono output for a 3rd channel. It worked fine then and a modified version should work now.
almarg's avatar
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almarg
8,673 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
Ag insider logo xs@2x
almarg
8,673 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
hhiggins's avatar
hhiggins
65 posts
 
Haven't heard the out of phase comment, but have heard 2 closely spaced speakers playing the same signal can have comb filtering effects (destructive interference affecting frequency response=peaks & nulls) Think your speakers are far enough apart that the effect would be minimal. I use 2 center channel speakers on either side of a 100" diag. screen, helps balance apparent "image size" between stereo front L & R and the center channel.
markphd
667 posts
 
If the speakers are different distances to your listening position, the sound waves from the two speakers will arrive at different times and can cancel each other out, or amplify each other, at the various different frequencies. I suspect that is what was meant. Even moving your head a few inches can cause this with the higher frequencies.

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.
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