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#151155 - 11/12/06 07:30 PM Center channel
stephrich1 Offline
newbie

Registered: 04/01/06
Posts: 3
Hi

I install my center above my screen and sometime I can ear the sound coming from above my screen.

Would it be ok to buy another one and put it under my screen and plug both to the one main center channel into my receiver would that work and be ok for my receiver?

Stephrich1

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#151156 - 11/12/06 08:10 PM Re: Center channel [Re: stephrich1]
St_PatGuy Offline
axiomite

Registered: 03/07/05
Posts: 7413
Loc: Glendale, Arizona
Have you tried angling it so it points right at you? May help some. I put a couple of rubber washers under mine to point it up towards my ears. Helped.
_________________________
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"Nothin' up my sleeve. . ." --Bullwinkle J. Moose

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#151157 - 11/12/06 08:26 PM Re: Center channel [Re: stephrich1]
SirQuack Offline
shareholder in the making

Registered: 01/29/04
Posts: 13344
Loc: Iowa
Are you saying a projection screen? If you mounted it above the screen, then it makes sense that the sound would seem to be coming from above, that is where you mounted it? Anyway, you normally want to mount the center at the same height as the tweeters of your left/right mains, which should all be close to ear level when seating. This will give you the best soundstage.

Now some people do run two centers, but a lot depends on what your using to drive them? Also, depending on the "ohm" rating of your centers will determine if your receiver can drive two of them on the same channel. I believe using two 8ohm rated centers would be like a single 4ohm center(not sure how to do the math).
_________________________
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M22-OWM22-VP100-Denon2805
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#151158 - 11/12/06 10:45 PM Re: Center channel [Re: stephrich1]
JohnK Offline
shareholder in the making

Registered: 05/11/02
Posts: 10412
Steph, you haven't given much detail about your setup, especially how far above the screen the center speaker is. If it's only a foot or so and isn't much different from the main speakers, then angling it down to point at your ears usually gives an acceptable effect. If this doesn't work for some reason, then yes, it's possible to run speakers in parallel above and below the screen, which will form a "phantom" image in the middle of the screen.

When speakers are run in parallel, this reduces the net impedance that the receiver sees. The simple answer is that two 8 ohm speakers in parallel reduce the impedance by half, i.e. a resulting 4ohm nominal impedance. The actual general formula is that the reciprocal of the total impedance resulting when any number of speakers of any impedance are run in parallel is equal to the sum of the reciprocals of the individual speaker impedances, e.g., 1/T=1/8+1/8, 1/T=2/8, T=4(ohms).

Whether any particular receiver would have any problem would depend on the impedances of the speakers, how loudly the material was being played and the capability of the receiver.
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Enjoy the music, not the equipment.



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#151159 - 11/13/06 09:54 AM Re: Center channel [Re: stephrich1]
bugbitten Offline
connoisseur

Registered: 04/06/05
Posts: 2339
Loc: Madisonville, KY
Quote:

Hi

I install my center above my screen and sometime I can ear the sound coming from above my screen.

Would it be ok to buy another one and put it under my screen and plug both to the one main center channel into my receiver would that work and be ok for my receiver?

Stephrich1




Yes. I have centers above and below. Really ties the dialog to the screen.

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#151160 - 11/15/06 12:01 PM Re: Center channel [Re: SirQuack]
biggsly5000 Offline
local

Registered: 11/30/04
Posts: 205
Loc: Atascocita, TX
If you want to connect 2 speakers to your amplifier, the best way for you to do it would probably be in series. This is the safest way for your amplifier. As described below:

"Series Connection:
This will explain how the impedance changes when speakers are connected in series. In a series connection you simply connect the positive terminal of speaker 'A' to positive terminal of the amplifier. Then you connect the negative terminal of spkr 'A' to the positive terminal of speaker 'B'. Lastly connect the negative terminal of speaker 'B' to the negative terminal of the amplifier. If both of the speakers have an impedance of 4 ohms, the total impedance will be 8 ohms. In a series connection, you simply add the individual impedances. If there were three 4 ohm speakers in series, the total impedance will be 12 ohms."

As for the volume level Audioholics has this to say:

"So how does this equate to sound pressure levels?

Since we connected two identical speakers in series with our amplifier, each speaker only sees half the voltage drop across it thus as a result will see only 1/4 the power delivered to each speaker compared to a single speaker connected to our amplifier. The equivalent SPL now produced by each speaker is 6dB lower than if a single speaker were playing off the amplifier, for a combined overall -3dB drop. However, running two speakers effectively doubles the volume displacement compared with that of one speaker. Thus playback through the two drivers results in a 3dB gain. Adding this to the 3dB drop previously mentioned and the net overall sound pressure level will remain unchanged. Thus, playing two identical speakers connected in series off of a common amp (as opposed to playing just one speaker off that amplifier) results in no level drop, when compared to the single speaker case. This analysis, of course, ignores mutual coupling and any room-induced acoustical artifacts. However, if the speakers connected in series are not co-located and summing perfectly in the room, the net SPL would likely be up to -3dB lower than playing a single speaker off the same amplifier. The net SPL product in this case has a dependent relationship on distance between the speakers and frequencies they are destructively interfering in the room."
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M80ti's, VP150, QS8's

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#151161 - 11/18/06 12:07 PM Re: Center channel [Re: JohnK]
stephrich1 Offline
newbie

Registered: 04/01/06
Posts: 3
Hi

My center is directly above my screen it's a tight fit between the screen and the ceiling.

Thanks for all the advice. I'll see if I can manage to tilt it down a little bit more or I will have to buy another one I guest

Thanks again

Stephane

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#151162 - 11/18/06 01:48 PM Re: Center channel [Re: stephrich1]
bugbitten Offline
connoisseur

Registered: 04/06/05
Posts: 2339
Loc: Madisonville, KY
Quote:

Hi

My center is directly above my screen it's a tight fit between the screen and the ceiling.

Thanks for all the advice. I'll see if I can manage to tilt it down a little bit more or I will have to buy another one I guest

Thanks again

Stephane




What is your set-up for mains? If you try a phantom center set-up, do you get the sound placement that comes closer to what you want?

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