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Dual center channels?
#158567 02/14/07 08:02 PM
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I’ve been seeing a bit of discussion about dual center channels, what kind of benefit would you get from using 2 m3’s instead of 1 VP 100 or 150. I would like to know how people are connecting 2 channels when there is only one center channel output on the Receiver. I plan on buying a Newcastle R771 which is rated to drive 4ohm loads so if I connected 2 centers to the one output would the receiver be able to handle this or do it require some extra equipment. I’d also like to know about placement options, do they go vertical or horizontal? I’d like some opinions on what benefits this would bring and how it can be done without spending extra money on a receiver or other devices becides the extra center of-course,

Re: Dual center channels?
kevin_obrien #158568 02/14/07 08:11 PM
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If you are going to be connecting 2 bookshelf models together, they need to be place vertically, otherwise you are kind of missing the point of getting a bookshelf.

There have been some studies suggesting that a speaker with a vertical placement has a wider horizontal dispersion than a horizontally configured one.

You have 2 options on how to connect them:

Series and Parallel (image courtesy of pmbuko)



If you wire them in Parallel, you will gain a 3db output from your speakers but your impedance will drop by half. So if you are running 2 8ohm speakers, your new impedance will be 4ohm (your receiver shouldn't have a problem with this).

Parallel is the perfered method of running 2 speakers on the same channel.

A series connection will decrease your impedance by double, so running 2 8ohm speakers will give you a 16ohm impedance (really easy to run), but your db level output goes down (not sure by how much)

Edit: I should also add that the reason I wanted 2 speakers in parallel (I normally would have purchased 1 speaker) is because I am going to be putting one above and below my 92" projection screen, to make it sound like dialog is coming from the centre of the screen.

Last edited by Hutzal; 02/14/07 08:32 PM.

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Re: Dual center channels?
Hutzal #158569 02/14/07 08:24 PM
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Re: Dual center channels?
Hutzal #158570 02/14/07 09:05 PM
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Quote:

but your db level output goes down (not sure by how much)




Parallel connections of 2 of the same speaker would halve the impediance, thus doubling the power for a 3dB increase.

Series connections of the same 2 speakers would be the opposite; Double the impediance, cutting the amp power output in half, for a 3dB decrease.

The decision to connect series or parallel (or a combo of both for more than 2 speakers) is based upon keeping the impediance of the load within spec of the amplifier.


-Dave

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ravenmanor.com/cinema/
Re: Dual center channels?
Hutzal #158571 02/14/07 09:34 PM
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Quote:

Edit: I should also add that the reason I wanted 2 speakers in parallel (I normally would have purchased 1 speaker) is because I am going to be putting one above and below my 92" projection screen, to make it sound like dialog is coming from the centre of the screen.




Get yourself enough power and you can have two runs of 8ohm speaker sets (each set in series) in a parallel configuration, giving you four speakers with a total of 8ohm resistance.

1/R=1/(8ohm+8ohm)+1/(8ohm+8ohm)
R=8ohm


Play it loud...
Re: Dual center channels?
ctk #158572 02/14/07 10:10 PM
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I just made an interesting discovery that hopefully someone a lot smarter than I can figure out, which shouldn’t be too hard to find…..

When running the 22’s in parallel and then running the Audyssey set up, Audyssey tells me my center channel speaker is large, but also sets the distance to 23 feet. The speakers are 11 feet away.

When I run Audyssey with only one M22, it tells me the center channel speaker is small, and sets the distance to 12’.

Why?

Re: Dual center channels?
michael_d #158573 02/14/07 10:34 PM
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Quote:

I just made an interesting discovery that hopefully someone a lot smarter than I can figure out, which shouldn’t be too hard to find…..

When running the 22’s in parallel and then running the Audyssey set up, Audyssey tells me my center channel speaker is large, but also sets the distance to 23 feet. The speakers are 11 feet away.

When I run Audyssey with only one M22, it tells me the center channel speaker is small, and sets the distance to 12’.

Why?




I am interested in this too, what if the 24' setting is correct? it does the same thing with a sub correct? sets it at twice the distance?


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Re: Dual center channels?
michael_d #158574 02/15/07 12:54 AM
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Re: Dual center channels?
michael_d #158575 02/15/07 05:47 AM
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Mike, it's very simple: 2x11' is about 23'. Seriously, that appears to be a mystery, since running speakers in parallel shouldn't have any effect of making the sound arrive later than the physical distance would indicate(as happens with subs because of delays in their internal electronics).


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Re: Dual center channels?
JohnK #158576 02/15/07 03:24 PM
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Ya, I think it's a mystery too. I'm going with Tom's explanation. that smartass…..

I am guessing it has something to do with resistance sensed by the Marantz. I can't tell much of a difference in sound if I leave the distance at 23' or back it down to 11' whereas I can tell with the sub.


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