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2 Center Channel Speakers


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15 replies to this topic

#1 of 16 OFFLINE   snash22

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Posted December 22 2006 - 03:34 AM

I have been wondering whether it would be a good idea to have 2 center channel speakers, one above the TV and one below it. The goal would be to have the sound image coming from the center of the screen.

I did a search in this forum and found 1 person saying "bad idea" without any reason given and another person saying "comb filtering between them can be a problem".

So, is this just a bad idea? IS comb filtering really a problem? How is this is different than listening to a mono source with 2 speakers? The 2 center channel speakers would be identical, except perhaps for age.

If I was to do it, would I hook them up in parallel or series?

#2 of 16 OFFLINE   Arthur S

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Posted December 22 2006 - 04:54 AM

Hi Steve

2 centers is not really a problem. I have tried all kinds of different center channel speakers and positions and it doesn't make much difference. Comb filtering should not be a problem.

Can't comment on parallel or series, someone else should be able to answer that question.

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#3 of 16 OFFLINE   Bill Marsh

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Posted December 22 2006 - 05:45 AM

Not really an expert but have been using 2 centers for 5 years ----Boston Acoustic HD-7'S WTH NO PROBLEMS----connected each to the amp----so parallel hook-up. This was with my sony 53 " tv --both speakers ontop. Now i have gone front projection and use 3 speakers for center. An Energy 8 sub with wires hooked parallel to the HD-7's. Heard quite a few top quality centers but this setup sounds better. If you calibrate with a sound meter make sre that the 2 speakers are adjusted to match the others----otherwise the centers will predominate and probably stress your amp or reciever.
Personally---2 speakers stretch the sweet spot somewhat therefore the others in the room benefit by it. The center obviously carries the brunt of the dialog so the better you can make it sound the better the movie experience will be. I'm assuming the 2 speakers timbre match your main speakers?
By the way the sub i have crossed-over at 40 hz and up---so the brunt of Bass is handled by the large subs in the room.
Parallel or series hook-up----both work and sound about the same to me. Parrallel seems to be more logical to me unless your wires are 12 gauge and you can't twist 2 together and fit them to your amp.
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Do not know which is better but my Home Theater is travelling at the speed of light AND sound. Yippee-ki-yay.

#4 of 16 OFFLINE   drobbins

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Posted December 22 2006 - 06:16 AM

I have been running 2 centers for a few years now. With a 104" screen, the dialogue was coming from below the screen. To me it was very distracting. I upgraded my center, but still bothered me so I added the original above the screen. I also upgraded my front R & L speakers and added the old ones to the R back & L back. The room is set up for 7.1 but my receiver is only 6.1. Someday I will upgrade. Anyway I am running 9.2 with a 6.1 receiver and no troubles. The extra speakers are running in parallel. Each row of seating has it's own surrounds and the dialogue is coming from the center of the screen.

#5 of 16 OFFLINE   JohnRice

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Posted December 22 2006 - 01:53 PM

The potential problem with dual centers is more an issue when they are next to each other. There is a tendency to get a phase cancellation around 2KHz, which is detrimental to dialog. With 2 identical speakers oriented vertically, I don't think that should happen. Still, after having used dual centers for several years, once I got it out of my head it was the way to go, I went with a single center and have wondered why I ever used two. In the real world, it just doesn't seem to work out how you expect it to, but there is such a tendency to believe it is better, that you aren't willing
to see it probably isn't. If the problem is the sound coming from below the image, put the speaker above it. Also, don't forget that running 2 speakers in parallel cuts their effective impedance in half and can cause serious problems.

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The Music Part: Emotiva XSP-1, Thiel CS 3.6, Emotiva XPA-2, Marantz SA8004, Emotiva ERC-3, SVS PB-12 Plus 2

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#6 of 16 OFFLINE   snash22

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Posted December 24 2006 - 02:51 AM

Intersting responses. The speakers will be about 3 or 4 feet away from each other so I'm guessing that will not cause the 2KHz cancellation.
I guess some receivers can handle the impedance issues better than others, Better safe than sorry, I'll try them in parallel.

JohnRice - The only way I'll know if it is a good idea is if I buy the additional speaker and create a space for it to go above the TV. Then I'll forever swear it was better, even if I can't tell the difference Posted Image .

Arthur - You said "I have tried all kinds of different center channel speakers and positions and it doesn't make much difference".

Do you mean that it it didn't make any difference positive or negative so it wasn't worth it?

#7 of 16 OFFLINE   JohnRice

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Posted December 24 2006 - 05:58 AM

Quote:
Intersting responses. The speakers will be about 3 or 4 feet away from each other so I'm guessing that will not cause the 2KHz cancellation.

The 2KHz cancellation is not so much due to the distance between speakers as the distance between your ears. That part of the reason speakers rarely have more than one tweeter.

Quote:
I guess some receivers can handle the impedance issues better than others, Better safe than sorry, I'll try them in parallel.

Parallel results in half impedance, and is where the danger comes for your amp.

Personally, I would try to find the best positioning for one speaker rather then running two.

The Hybrid System

The Music Part: Emotiva XSP-1, Thiel CS 3.6, Emotiva XPA-2, Marantz SA8004, Emotiva ERC-3, SVS PB-12 Plus 2

The Surround Part: Sherbourn PT-7030, Thiel SCS3, Emotiva XPA-5, Polk & Emotiva Surrounds.


#8 of 16 OFFLINE   ChrisWiggles

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Posted December 24 2006 - 07:12 AM

I hate to disagree with all the above posters, but using two center channels is always almost unambiguously a terrible idea. You will get terrible comb filtering unless you perfectly phase align them for your position. If you have them side-by-side this means you only avoid combing on-axis horizontally, if you have them above and below this means that you will only get things correct through one elevation plane.

Strongly reccommend against using dual centers, it really is not appropriate if high-performance is your goal. The combing will be even nastier than what you get off-axis with an MTM center, and most people doing dual centers aren't aware of the combing problem (or they probably wouldn't bother in the first place) which means they've not phase aligned the speakers for the listening position which means they have no chance of even getting decent performance from this kind of setup.

#9 of 16 OFFLINE   JohnRice

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Posted December 24 2006 - 07:51 AM

Quote:
I hate to disagree with all the above posters
Apparently you didn't read the responses. There are those of us who have recommended against it, some repeatedly. I only stated that the OP is probably intent on doing it anyway and will not be perceptive to the many downsides.

The Hybrid System

The Music Part: Emotiva XSP-1, Thiel CS 3.6, Emotiva XPA-2, Marantz SA8004, Emotiva ERC-3, SVS PB-12 Plus 2

The Surround Part: Sherbourn PT-7030, Thiel SCS3, Emotiva XPA-5, Polk & Emotiva Surrounds.


#10 of 16 OFFLINE   ChrisWiggles

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Posted December 24 2006 - 08:17 AM

All, many, whatever. The point remains.

#11 of 16 OFFLINE   drobbins

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Posted December 24 2006 - 03:49 PM

I am using JBL speakers through a Yamaha receiver and use two centers for two reasons.
    [*]To hear the dialogue better. I originally had a small center (4"x6" came with the set) that could not handle the task. I upgraded to the JBL EC35 center. I could hear the dialogue much better, but created a second issue. I often found myself looking at the bottom of the screen where the sound was coming from.[*]To center the dialogue to the center of the screen & not below it. Before I added the second center I upgraded my R & L fronts to E30s. I calibrated, used the SPL meter, frequency sweeps, etc... but still didn't help. So I put the little 4X6 speaker above the screen.
I had read about all the issues that it could cause but thought I would try it anyway. I had a big improvement in my sound to visual perception and I could hear the dialogue better. I understand what combing is from reading about it, but by listening I don't hear an issue. Granted that a better system might do the job with out 2 centers, but working with what I have, it solved my issues. My Yamaha receiver hasn't complained one bit.
Dave

#12 of 16 OFFLINE   JohnRice

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Posted December 24 2006 - 04:23 PM

Dave, the fact you are using 2 radically different speakers as dual centers, and find the result to be acceptable, I'm not sure your perceptions are all that reliable. I understand how a center below the image is annoying, that is why I always place it above the screen.

The Hybrid System

The Music Part: Emotiva XSP-1, Thiel CS 3.6, Emotiva XPA-2, Marantz SA8004, Emotiva ERC-3, SVS PB-12 Plus 2

The Surround Part: Sherbourn PT-7030, Thiel SCS3, Emotiva XPA-5, Polk & Emotiva Surrounds.


#13 of 16 OFFLINE   drobbins

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Posted December 25 2006 - 06:17 AM

Hey, Merry Christmas Posted Image
Quote:
I'm not sure your perceptions are all that reliable.

Maybe , maybe not. But after playing around with different settings & with one or two speakers, it is what sounds best to me. How would you suggest for me to tell what I am missing? Putting the better center above the screen is not an option due to a low ceiling height.

#14 of 16 OFFLINE   ShoestringHT

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Posted September 13 2010 - 03:42 PM

I tried the two center thing, it was okay. I had the same issues with my 47" LCD there is really no good place for the center if you tv is on a stand, beside below screen and in front. I am getting ready to finish my basement and put in my HT area. I have actually corrected my imaging issues by purchasing JBL control Now AWspeakers  I got these on ebay re-manufactured from harmon kardon. i paid between 35-58 dollars including shipping. These things are amazing the clarity is outstanding i got 7 of them it took 2 weeks but well worth it. I am powering them with a Yamaha RX-V2600 (in my opinion Yamaha is the best) They are uniquely designed with a centered tweeter and a 4 inch speaker on each side making them very very versatile in placement. They are in a quarter circle enclosure and weigh about 8lbs.each. It is very much worth checking them out not to mention all of my digital music sounds awesome as well



#15 of 16 OFFLINE   smithb

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Posted September 14 2010 - 07:24 AM

.



#16 of 16 OFFLINE   cme4brain

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Posted July 09 2014 - 05:44 PM

Not really an expert but have been using 2 centers for 5 years ----Boston Acoustic HD-7'S WTH NO PROBLEMS----connected each to the amp----so parallel hook-up. This was with my sony 53 " tv --both speakers ontop. Now i have gone front projection and use 3 speakers for center. An Energy 8 sub with wires hooked parallel to the HD-7's. Heard quite a few top quality centers but this setup sounds better. If you calibrate with a sound meter make sre that the 2 speakers are adjusted to match the others----otherwise the centers will predominate and probably stress your amp or reciever.
Personally---2 speakers stretch the sweet spot somewhat therefore the others in the room benefit by it. The center obviously carries the brunt of the dialog so the better you can make it sound the better the movie experience will be. I'm assuming the 2 speakers timbre match your main speakers?
By the way the sub i have crossed-over at 40 hz and up---so the brunt of Bass is handled by the large subs in the room.
Parallel or series hook-up----both work and sound about the same to me. Parrallel seems to be more logical to me unless your wires are 12 gauge and you can't twist 2 together and fit them to your amp.

 

All of thegobbledegook about interference waves from dual center speakers.  If the writer uses them- or three- and likes the results, then the theoretical problems don't apply!




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