Connecting two center speakers to UPA-1

[ottaone]

I have two idle B&W 601s lying around and while waiting for a good deal on an Emo ERM6.3, I'm thinking of using two centers instead of one. Since I want to increase the SPL (room is now LxWxH - 20'x17'x19'), I imagine that I will connect them in parallel.

Would folks chime in on the following:

1) Should I use two centers - that is pros outweigh the cons
2) Connect in parallel or series
3) Will a UPA-1 handle two in either parallel or series?
4) Other important considerations

TIA

[butchgo]

I am using two ERM-1s for a center channel and I am very impressed with the results.
I have them wired in parrallel so the impedence is actually 2 ohms but my Outlaw 7500 doesn't seem to mind.
If your 601s are 8 ohm you really shouldn't have a problem driving them with the UPA-1 wired in parallel but I would try wiring them both ways and see which sounds best to you.
I am like you waiting for a deal on a 6.3 but everytime they show up on the forum somebody alyways beats me to them and Emotive will not have anything in until October.

[jackfish]

There are two positive(red)/negative(black) speaker terminal pairs on the UPA-1. It would be like running them in parallel if you connected each speaker to a separate and individual positive/negative speaker terminal pair. The resulting impedance would be 4 Ohms.

The other consideration I can think of is whether or not there will be comb filtering/phase interference if they are placed too close to each other. If they are separated by the width of a large screen TV it probably won't be an issue.

[butchgo]

People always talk about the "combing effect" but I have never really understood what this means.
I tried wiring my ERM-1s in series and they sounded very weird, like they were trying to cancel each other out or something but wired in parallel they sound great.

[DYohn]

Sept 1, 2010 13:40:16 GMT -5 butchgo said:

People always talk about the "combing effect" but I have never really understood what this means.
I tried wiring my ERM-1s in series and they sounded very weird, like they were trying to cancel each other out or something but wired in parallel they sound great.

Combing is what happens when the same signal is being produced by two sources that are in the same listening space. It occurs because the signal from each source arrives at the listener's position at slightly different times, and the sound wave from one source arrives out of phase with the other, causing signal cancellation (it also causes signal level increases depending on how the phases interact at any given position in the room.)

This effect will occur sometimes in some locations every time more than one speaker is reproducing the same signal. Whether it has negative effects or is even noticeable will be different in every setup and will change anytime the signal changes, and the effect will vary anytime the listener changes position.

In the vast majority of instances, the net effect is moot and the listener never notices it at all.

[butchgo]

Thank you for the explanation.

[jmilton]

Dyohn said it well...but just to add to perfection, you might read this small article:

forum.ecoustics.com/bbs/messages/34579/572305.html

[ottaone]

Sept 1, 2010 14:33:38 GMT -5 DYohn said:

...

In the vast majority of instances, the net effect is moot and the listener never notices it at all.

Thanks gents. I'm picking up on what I want to hear. I would think that my instance is included in dyohn's "vast majority of instances". I think that where I sit (or lie down) in the family room means that I may never notice any combing effect.

I will certainly try the two 601s in a variety of configuration - two tweeters on the inside, standing up side by side, with spaces in between, etc.

Good point about the two sets of binding posts in the UPA-1. I've just been used to bi-wiring the 601s (free bi-wires from my dealer) that I didn't think of using these wires to drive two speakers.

Finally, I don't see any big warnings from anyone so I'll do it ... pronto.

[wuzzzer]

I look at the two center speaker thing this way. If there were any benefit to doing it, speaker manufacturers, receiver manufacturers, etc. would have added this feature long ago. The fact that it isn't there must mean something. Don't you think speaker companies would love to sell more speakers?

Here is an illustration of what happens with comb filtering:



It presents low ohm loads that many amps don't handle well and negatively affects the sound you hear.