How to connect two Speakers to the Center Channel Output - Page 2 - AVS Forum
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post #31 of 41 Old 11-06-2007, 07:30 PM
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Originally Posted by psgcdn View Post

12 dB per octave is still pretty steep. A signal 10 dB down shouldn't be audible over the same frequency at full strength from another driver.

Sure and any cancellations will be reduced simply because there's less energy to begin with. The half-wavelength estimate is rule-of-thumb and, obviously, is dependent on other variables.

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post #32 of 41 Old 11-06-2007, 07:32 PM
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Quote:
Originally Posted by craig john View Post

The two speakers are 16.25" apart. Therefore in order to to almost completely eliminate any interference, the first woofer should start to "taper out" at about 300 Hz with a steep crossover. The actual taper point is 550 Hz and not real steep, (12 dB/octave, IIRC). Nonetheless, that is much better than most MTM horizontal CC's that run both mid-woofers all the up way to the crossover with the tweeter.

As I said, "my CC doesn't have too much issue with lobing". I didn't say it was perfect!

Craig

Agreed. The proof of the pudding is in the listening. OTOH, it might be interesting to run a pink noise signal through it and view the RTA as you move the mic. Or mebbe not.

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post #33 of 41 Old 11-07-2007, 06:55 AM
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Quote:
Originally Posted by Kal Rubinson View Post

Agreed. The proof of the pudding is in the listening. OTOH, it might be interesting to run a pink noise signal through it and view the RTA as you move the mic. Or mebbe not.

In terms of listening, I almost never sit outside the sweet spot. However, because of this discussion, last night I tried several spots outside the sweet spot. Standing above and behind the sweet spot revealed no serious issues, other than that the dialogue imaged too low, (my CC is on a 30" stand which places it 1" below the screen material, 14" in front of the screen wall and angled up towards ear level). Sitting to the left or right of the sweet spot revealed no serious diminution of SQ until I got outside the periphery of the left or right mains. At that point, the sound got a little hollow sounding, especially deep male voices. However, the sonic image stayed pretty well locked to the CC at all seating positions, including the distant ones.

I don't have an RTA. What would you predict the results to be? (I might be able to borrow one, if it would be worth it.)

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post #34 of 41 Old 11-19-2007, 11:01 AM
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Just to add a little fuel to the fire...

How would you guys suggest orienting a pair of Def Tech CLR-1000 center channel speakers? Horizontally or vertically? The idea of placing one above the screen and one below to create a phantom image that is centered vertically on the screen is interesting, but I can't really go there at this point in time.



Before anyone says this is a dumb idea or I wasted money on mediocre center channel speakers, etc., I'll add that I picked these center channels up for a great price and the drivers exactly match the rest of the Def Tech BP speakers that I have. They're used mainly for HT. Just experimenting here. If it doesn't "work" or isn't ideal, I can always change it.

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post #35 of 41 Old 11-19-2007, 11:37 AM
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Quote:
Originally Posted by craig john View Post

In terms of listening, I almost never sit outside the sweet spot. However, because of this discussion, last night I tried several spots outside the sweet spot. Standing above and behind the sweet spot revealed no serious issues, other than that the dialogue imaged too low, (my CC is on a 30" stand which places it 1" below the screen material, 14" in front of the screen wall and angled up towards ear level). Sitting to the left or right of the sweet spot revealed no serious diminution of SQ until I got outside the periphery of the left or right mains. At that point, the sound got a little hollow sounding, especially deep male voices. However, the sonic image stayed pretty well locked to the CC at all seating positions, including the distant ones.

I don't have an RTA. What would you predict the results to be? (I might be able to borrow one, if it would be worth it.)
Craig

The variation is over smaller increments and the RTA should show variability in the crossover region.

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post #36 of 41 Old 11-19-2007, 01:08 PM
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Quote:
Originally Posted by btp View Post

Just to add a little fuel to the fire...

How would you guys suggest orienting a pair of Def Tech CLR-1000 center channel speakers? Horizontally or vertically? The idea of placing one above the screen and one below to create a phantom image that is centered vertically on the screen is interesting, but I can't really go there at this point in time.



Before anyone says this is a dumb idea or I wasted money on mediocre center channel speakers, etc., I'll add that I picked these center channels up for a great price and the drivers exactly match the rest of the Def Tech BP speakers that I have. They're used mainly for HT. Just experimenting here. If it doesn't "work" or isn't ideal, I can always change it.

You should only use ONE of them and vertically if possible. The way that you have them pictured is a terrible solution.

Use the extra one for a 6th speaker if you don't already have a 6th speaker. Otherwise, put it in the closet, attic, or basement.

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post #37 of 41 Old 11-19-2007, 01:12 PM
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Thanks, but I just set the one speaker on top of the other way to take a quick picture. I knew it wouldn't be long before someone said I should only run ONE of them. While that was not my question, please tell me why running two of them side-by-side is such a terrible idea. I mean, honestly... how bad it could it POSSIBLY affect imaging and FR?

I'm not afraid to "break the rules" and at least try it out to see how it works for myself. Absolutely nothing to lose.

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post #38 of 41 Old 11-19-2007, 01:24 PM
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Quote:
Originally Posted by btp View Post

While that was not my question, please tell me why running two of them side-by-side is such a terrible idea. I mean, honestly... how bad it could it POSSIBLY affect imaging and FR?

I'm not afraid to "break the rules" and at least try it out to see how it works for myself. Absolutely nothing to lose.

I don't know what you mean by "side-by-side". If you mean one on either side of the screen, used vertically, doing so creates unwanted acoustic anomalies.

Just as you use one single speaker per each of your other channels, so should you do so with your center channel.

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post #39 of 41 Old 02-17-2013, 08:02 AM
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Interesting. After reading most of the posts I was very concerned that my thought to have two Definitive CLR3000's under my 120" screen was going to result in a detriment to sound quality and possibly volume. Since I had already made an offer on another CLR3000, I was stuck. I just figured I'd give it a go anyway and see at happens. Original setup had just one CLR3000 under the center of the screen flanked on the left by a DefTec Powerfield 1500 sub. (BP2000's run Front L/R and Rear L/R. BPX's run Front Presence) Now I have the sub in the center flanked on both sides by the CLR3000's. I ran multiple back to back tests with just one center running and then both. I have to say, I like the 2 center option a little better. There seems to be a little better balance in all seating positions. Do I have to run two?...no. It would still be just fine with one but I didnt hear any of the drastict hits to quality that some suggested. I'm listening to audio right now, as I write this, and can honestly say I dont hear any detriment to imaging or compounding or cancellations of frequencies. I can unplug one of the centers or move to an adjacent seating position it sounds the same to me other than the seating positions L/R of center getting a little more L or R channel volume. Using an NAD 272 to power the centers. Anthem MCA-5 to power the BP2000's.
This is my first post and I'm not looking for it to be contentious. Just thought I would relay what I perceived in my setup. Perhaps given my room setup and equipment, I just got lucky with this arrangement.
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post #40 of 41 Old 02-17-2013, 09:54 AM
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I said this 6 years ago in this thread and it's still true for me:

I've never heard comb filtering (and I'm happy with music from only two speakers with a rock-solid phantom image)

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post #41 of 41 Old 02-18-2013, 07:42 PM
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Quote:
Originally Posted by craig john View Post

Well, I'll play devil's advocate for a minute. I was at the Audioholics Show in Clearwater, FL a few weeks ago and Axiom Audio had a room with a 7.1 system using 2 CC's, one above and one below the screen. I asked Ian Colquhoun, owner and founder of Axiom Audio and lead speaker designer, why they were doing that. He responded that it helps to center the audio image on the screen heightwise. With just one center, either above or below the screen, the audio image is pulled higher or lower than the video image. Two centers, one above and one below provides a "phantom" image in the middle, heightwise.


Knowing the "conventional wisdom" on this forum, I raised an eyebrow and sceptically sat down in the sweet spot. Sure enough, he was right; the audio image was higher and the dialogue was better locked to the image. My CC at home is located one inch below the screen and about 8 inches below the tweeter height of the L/R's. I can occasionally notice sounds, especially dialogue that is localized below the screen, so I am sensitive to this. I asked him about the "comb filtering" that is possible with two speakers mounted this way. His reply was that the ear/brain doesn't really "hear" comb filtering. I'm not sure exactly what comb filtering sounds like, but I didn't hear anything bothersome from the two CC's.


Also, the system was using Axiom's new 8-channel amp, so each CC was driven by it's own amp, eliminating the problem of using the same amp for both speakers.


I would want to spend more time using such a system before I would outright recommend it to someone. Nonetheless, I was surprised that the conventional wisdom of this forum that we should never use two CC's was not absolutely confirmed, as I expected it would be.


Craig

We have the same set up (above and below) and our last home theater had a similar one. We have a 110 inch projection system and seating is about 12 feet from the screen. The sreen is a DaLite High Power, which is not perforated. To anchor the dialog to the screen (without an acoustically perforated screen), I decided to go high/low.
I have one of the centers under the screen at floor level. It is angled up slightly (with a laser pointer) to aim the tweeter at ear level. I have a second center above the screen with the tweeter aimed down to ear level.
To solve the balance (and AVR amp load) problem, I purchased an separate stereo amp. (HK). I split the center channel preamp output of the AVR (Pioneer SC35) with an rca "Y" and send the two identical signal(s) to the amp. I turn on the amp with a 12 volt trigger from the AVR , so when it powers on and off the amp does as well. So, I feed each of the center channel speakers with the R/L output of the stereo amp. I balance the total 7.1 system with the AVR MCAC. It "sees" the total sound energy coming from the two centers as the "one" center channel. The trim adjustments (volume controls) on the amp allow me to tweak the output of each center speaker "channel" to bring the phantom image of the dialog to the upper third center of the screen. It works like a charm.smile.gif
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