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#205646 - 04/27/08 09:32 AM combing effects of dual center channels
kuro Offline
newbie

Registered: 04/25/08
Posts: 2
Loc: monroe , ny - USA
I have always believed that dual center channels are a major sin when setting up a home theater, due to the obvious combing effect created by the output of each speaker arriving at different times. It's a highly technical achievement to "Design" a speaker to be time coherent , let alone set up two seperate speakers on one channel expecting clean arrivals. Recently I have noticed talk in various forums and articles professing two center channels as an improvement . I am open to new ideas and advancements , being in this avocation long enough to realize that nothing is carved in stone . I would welcome any comments !!

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#205648 - 04/27/08 10:23 AM Re: combing effects of dual center channels [Re: kuro]
SirQuack Offline
shareholder in the making

Registered: 01/29/04
Posts: 13333
Loc: Iowa
Many on this forum use dual Axiom centers with great results, especially for projection screen setups. Keep in mind your ohm rating will be cut in half for that channel, so your AVR should be able to handle the lower rating.
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#206268 - 04/30/08 02:17 PM Re: combing effects of dual center channels [Re: kuro]
alan Offline
connoisseur

Registered: 01/29/02
Posts: 3187
Loc: Toronto/New York/Dwight
Hi kuro,

While combing effects are easily heard using a pink-noise test signal (and are measureable), they are not significant or audible with music or soundtrack playback.

Moreoever, any speaker or two speakers produce comb-filtering effects. Try it with one speaker and pink noise. As you move your head slightly to one side or the other--only a few inches are necessary-- the arrival times of sounds to each of your ears change as your head changes position and the distance from the speaker driver to each ear changes, resulting in audible comb-filtering effects. You'll hear the high-frequency content alternately increase and decrease because of cancellation and reinforcement.

The notion of time-coherency when put to the test under controlled listening conditions is a lot of high-end blather not based on scientifically controlled listening tests.

It simply doesn't matter with music or soundtrack playback. If we were all ultra-sensitive to combing effects with musical playback from loudspeakers, we'd all be complaining. It would be intolerable.

Regards,
_________________________
Alan Lofft,
Axiom Resident Expert

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#206345 - 04/30/08 08:11 PM Re: combing effects of dual center channels [Re: alan]
NDinUSA Offline
veteran

Registered: 12/24/07
Posts: 119
Loc: Fargo, ND USA
I have a dual VP150s (one above the screen and one below the screen). I thinks this works very well. It makes the voices seem like they are coming from the center of the screen. I run the centers on their own separate amplifier channels so I don't have to worry about the ohm rating of the centers as Sirquack states.
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#206347 - 04/30/08 08:58 PM Re: combing effects of dual center channels [Re: NDinUSA]
rodzrod Offline
newbie

Registered: 04/30/08
Posts: 2
Loc: Melbourne, Australia
Having read your comments so far, am I right in assuming that 2 bookshelf speakers used for the centre channel would work well either side of a 42" screen? Or should I stick with the taditional one centre speaker approach? I am planning to run them through an Onkyo SR875 or simmilar receiver.


Edited by rodzrod (04/30/08 09:04 PM)

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#206353 - 04/30/08 09:10 PM Re: combing effects of dual center channels [Re: rodzrod]
jakewash Offline
shareholder in the making

Registered: 12/26/03
Posts: 10398
Loc: Calgary, Alberta
That is up to you, I think if your mains are far enough away from the sides of the TV to provide ample channel seperation then 2 bookshelf speakers on either side should work fine. I would try to make sure they are mounted about midline of the screen to ensure a centered sound. The single center is always there as a back up plan as we know it pretty much works no matter what.
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Jason
-----------------
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#206406 - 05/01/08 08:58 AM Re: combing effects of dual center channels [Re: jakewash]
nickbuol Offline
connoisseur

Registered: 09/16/04
Posts: 4449
Loc: Marion, IA
Keep in mind that human ears can sense a difference in left vs. right, but have a much more difficult time sensing a difference up or down (within a theater environment anyway), so putting a speaker to the left and another to the right of the screen/tv or whatever will not be as effective in really holding the center channel vocals and sounds to the screen. Your ears will blend them into the right and left front channels. I wouldn't do it, even with a good amount of separation between these two left/right centers and the left/right fronts.
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#206417 - 05/01/08 11:05 AM Re: combing effects of dual center channels [Re: alan]
vassillios Offline
aficionado

Registered: 02/28/07
Posts: 597
Loc: Warrenton, VA
 Originally Posted By: alan
Hi kuro,

While combing effects are easily heard using a pink-noise test signal (and are measureable), they are not significant or audible with music or soundtrack playback.

Moreoever, any speaker or two speakers produce comb-filtering effects. Try it with one speaker and pink noise. As you move your head slightly to one side or the other--only a few inches are necessary-- the arrival times of sounds to each of your ears change as your head changes position and the distance from the speaker driver to each ear changes, resulting in audible comb-filtering effects. You'll hear the high-frequency content alternately increase and decrease because of cancellation and reinforcement.

The notion of time-coherency when put to the test under controlled listening conditions is a lot of high-end blather not based on scientifically controlled listening tests.

It simply doesn't matter with music or soundtrack playback. If we were all ultra-sensitive to combing effects with musical playback from loudspeakers, we'd all be complaining. It would be intolerable.

Regards,


that's what I was going to say....yeah right!
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Made on a Mac

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#206424 - 05/01/08 11:53 AM Re: combing effects of dual center channels [Re: nickbuol]
alan Offline
connoisseur

Registered: 01/29/02
Posts: 3187
Loc: Toronto/New York/Dwight
Hi,

Nickbuol is quite correct in this. I'd be reluctant to try dual centers to either side of a video display. If you were centered in the sweet spot exactly mid-way between the two centers, then that would be fine. It would phantom image the dialog exactly at the screen center. But for anyone sitting slightly to one side or the other, the dialog would default to one of the dual centers closest to the viewer, which would move the dialog to the left or right of the screen--not desirable.

Dual centers only work well, above and below the display, not to either side.

Regards,

Alan
_________________________
Alan Lofft,
Axiom Resident Expert

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#206484 - 05/01/08 03:55 PM Re: combing effects of dual center channels [Re: alan]
jakewash Offline
shareholder in the making

Registered: 12/26/03
Posts: 10398
Loc: Calgary, Alberta
Good point Alan, I had forgotten about that off center listening position issue. Looking back at when I had my M22s set up on the side, it was just like that, when off to the left the left speaker was more prominent.

Don't do center speakers on the sides.
_________________________
Jason
-----------------
TTTHHHPPPPPTTTT!

My HT

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