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Center-Channel Problem

Scott Wilkinson  |  Nov 18, 2011

I have a problem with my dedicated home theater—my center channel doesn't always sound clear. I've heard other systems whose dialog is crystal clear, but mine isn't. My system includes Klipsch speakers (RF-83 fronts, RC-64 center, RB-81 rears), two Velodyne DD-15 subwoofers with SVS AS-EQ1 equalizer, Anthem Statement P5 5-channel power amp, and Integra DHC-9.9 pre/pro. I've attached a photo of where my center-channel speaker sits, plus another one of the front of the theater. Any advice would be appreciated.

Rick Audinot

The problem is crystal clear from your first photo (shown above)—the center speaker is placed within a cabinet. All freestanding speakers, including the RC-64, are intended to be positioned with lots of free space around them (hence the term "freestanding"). This allows the sound to expand freely around the speaker. If you place it in a cabinet, the sound can get muffled and distorted. Granted, the RC-64 is a sealed-box design—your problem would be worse with a ported-box speaker, especially one with the port on the back—but still, I think the best solution is to get the center speaker out of that cabinet and onto the shelf above it.

From your first photo, that would mean raising the screen a few inches. But from your second photo (shown above), that might not be possible, given how close the screen is to the ceiling already.

You could put the center speaker on a tall stand on the floor, but that would be pretty ungainly in your otherwise elegant theater. (I wouldn't put it on a short stand on the floor, because it would be far from the screen in that case, and the front seats would block its sound from the seats behind them.) Another solution would be to get a slightly smaller screen that allowed enough room below it for the center speaker on the top of the equipment cabinet. If you watch a lot of movies, you might consider a 2.35:1 screen, which would give you plenty of room for the center speaker, though replacing your current screen would be expensive.

The easiest but least desirable solution is to EQ the center channel to compensate for the cabinet's effect on the sound. This might improve things somewhat, but not as much as placing the speaker in free space.

Update: Another option, mentioned in the comments below, is to add damping material inside the cabinet. THX recommends using a poly batting material similar to that found in pillows, filling the space behind the speaker so that it's moderately firm but not stiff. This will help reduce the resonances within the cabinet and clean up the sound from that speaker. You can also build a baffle around the front of the speaker to isolate the front from the interior of the cabinet.

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COMMENTS
juanseva_2's picture
Submitted by juanseva_2 on November 18, 2011 - 1:16pm

I had the same problem
Having identified a possible cause (panel loose or weak), I corrected the problem by adjusting the panel very well where he was positioned my center speaker, although I have not much space around the speaker. In that same piece of furniture is the amplifier, and above central speaker. My center speaker is a bose vcs-10, which has much less power and performance than the RC-64, and this problem happened.
Vibrational waves generated by the speakers, particularly at high odds sound vibrations cause nearby items that interfere with the clarity and purity of sound.

Is There some material that can be used to recommend us to isolate the feet of the speaker to forniture? I have bose Bose 301 Series V Direct Reflecting book shelf speaker, and they themselves are free and have plenty of space around, although I notice that at high volumes, this phenomenon of distortion starts to happen a bit.

any comments would be helpful. Thank you.

yachtmandu's picture
Submitted by yachtmandu on November 18, 2011 - 7:13pm

I'd simply remove the cabinet door and shorten it so the center channel is exposed and the other gear is still hidden behind the new smaller cabinet door. Put the black grill cloth back on the center speaker, re-calibrate, and bob's your uncle.

mailiang's picture
Submitted by mailiang on November 18, 2011 - 10:28pm

I have my center channel placed on the shelf of my audio cabinet right underneath my TV with out any issues. You may want to also try opening the rear of the cabinet if you can, to reduce any reflections or standing waves which can have a negative effect on the linearity of your speakers frequency response.

mcraeh's picture
Submitted by mcraeh on November 19, 2011 - 3:54am

i have a similar klipsh center in my salamander rack. its in the rack but is exposed, with no door etc.... i used some rubber isolating feet to position the center to point up just a little and decouple it. it has always seemed fine. although now since reading this i may have to try it the other way with it just sitting on the rack.

Ropro's picture
Submitted by Ropro on November 19, 2011 - 6:10am

Buy acoustically-invisible cloth; then install not only in front of centre channel speaker but in front of right and left front speakers (it would hide them and it would homogenize the mild sonic dampening). I also agree that the centre speaker should have as much free space around it as possible to permit it to perform to its full potential.

Jarod's picture
Submitted by Jarod on November 19, 2011 - 8:42am

Ya great looking theater but you gotta give that big center channel some breathing room.

Nyal Mellor's picture
Submitted by Nyal Mellor on November 19, 2011 - 8:57am

As others have said the best solution is to shorten the existing door and either have the center channel just sitting there on its shelf or cover the opening with speaker grille fabric.

My addition to this would be to recommend cutting either fiberglass (rigid FR701 type) or acoustical cotton (better for you since you dont have to worry abou stray fibers) so that it forms a baffle around the speaker front and fills in the gap between the front and the sides of the shelf. You should also stuff acoustical cotton into the cavity around and behind the center speaker to prevent and damp any resonances.

Nyal / Acoustic Frontiers

true audio's picture
Submitted by true audio on November 21, 2011 - 5:19am

Great looking theater! My suggestion would be the same and get a center channel stand for you speaker.It could breath, raise the height and you could slightly tilt it upward if needed. But first you would have to get rid of the big av box underneath your screen or rebuild it someway.Is there anyway to have all your av gear off to the side. Can you mount in wall? You could get a nice rack and put a glass front door on it.It would be clean and look great.To me,a great center channel is everthing and your situation would drive me nuts. Why worry about hiding your center channel if all your other speakers are exposed ? I hope this helps you some. Happy movie watching!

mailiang's picture
Submitted by mailiang on November 20, 2011 - 3:26pm

Since we haven't heard from the op, in defense of the other posters, I don't believe it is accurate to suggest that their recommendations can't solve his problem. If it is unreasonable for him to move the speaker, using damping materials and modifying the enclosure may be a workable solution.

Scott Wilkinson's picture
Submitted by Scott Wilkinson on November 21, 2011 - 11:04am
You're right that adding damping material inside the cabinet is another way to help the situation. THX recommends a poly batting material similar to that used in pillows and filling the space behind the speaker so that it's moderately firm but not stiff. Other helpful techniques include opening the back of the cabinet (not practical in this case) and installing a baffle around the front of the speaker to isolate the front from the interior of the cabinet.
johnnyd's picture
Submitted by johnnyd on November 21, 2011 - 10:57pm

As an alternative to rebuilding the cabinet, you could remove the left cabinet door in front of the speaker, and build a shorter one that leaves the speaker exposed. Then you could attach some metal rails, or heavy duty drawer slides and slide the speaker out into the room like an open drawer when your listening to the system, and slide it back in when not in use. Of course you would use the speaker grill in this case, and recovering it to match the door fabric is an option. You could also rework a slightly larger speaker grill that looks like the bottom door and would fill in all the empty space around the speaker when the speaker is slid into the cabinet. Then it would look like a top and bottom double door where the bottom door swings open, and the top door slides out. That would really be custom!

Scott Wilkinson's picture
Submitted by Scott Wilkinson on November 22, 2011 - 12:16pm
Both of your ideas are excellent! I especially like putting the center speaker on rails so it can be pulled out when in use.
chriscmore's picture
Submitted by chriscmore on November 22, 2011 - 4:13pm

Best practice would be to ditch the RC-64 and get a single RF-83 for an identical center channel. Timbre matching would be perfect and its vertical orientation would eliminate comb filtering and lobing by not having horizontally-aligned drivers reproducing the same frequencies. Also, having three RF-83s would be acoustically great as they would mandate having some airspace around them as others suggested, eliminating the smearing effects of early reflections.

This would likely require spacing the screen in front, which can be done with a false wall, or ceiling hung acoustically transparent screen, retractable or fixed.

Or, for a more built-in look, ditch the RF-83s and pickup two more RC-64s. Vertically align all three on the same axis, wall mounted in front of heavy acoustic absorption, and then go however big you want with the image; truly cinematic.

I know these solutions are not minor surgery, but they would get away from the undersized-screen and acoustical compromises that are too often done.

Cheers,
Chris Seymour

fastfredddy54's picture
Submitted by fastfredddy54 on November 28, 2011 - 2:49pm

I used a simple wallmount tv stand set just at the top of the monitor and placed my center channel on it. Very strong, invisible. Your system must be in reach of the stand however, and holes drilled into the wall behind the monitor.

albert26's picture
Submitted by albert26 on January 22, 2012 - 5:18pm

Why has no one suggested better cable, no bi-wire,strictly excellent wire from maybe MIT,Wireworld,STRAIGHTWIRE, There's all kinds of affordable wire out there,unless we are all still thinking,, Monster is the best ,,like Bose,,just kidding,,,again We are all smarter than a 5th grader.
Also Klipsch is a Horn loaded speaker ,,it should be screaming.
2 watts drive a Klipsch, especially if Paul made it,,,Anyways you need to check all Calibrations,at least with a DB meter,sometimes we all need professional help, like a Doctor,,good luck kid
brian www.floridahometheatersplus

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