High-Mounted or Ceiling-Mounted Bass Traps: Is Asymmetrical Okay?

Ron Resnick

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Do high-mounted or ceiling-mounted bass traps, when they are located well above the tops of the loudspeakers, have to be symmetrical on both sides of the room?

Imagine seven foot tall speakers in a listening room with a 15 foot tall ceiling. A large, hollow, wood-framed soffit descends four feet from the ceiling on the left side of the room (starting at the ceiling and continuing down from the ceiling for four feet on the left side wall). This soffit is six inches deep in some areas and four feet deep in the front left corner of the ceiling. The entire soffit, at each depth, is filled with blue jeans insulation. The front left corner section is four feet tall (like the entire soffit) but is four feet deep and filled entirely with blue jeans insulation.

The entire soffit is open to the blue jeans insulation; the soffit is not covered with drywall or any other solid or reflective material.

What effect will this large, acoustically-porous, sound-absorbing, high-located area have on the acoustics of the room?

Will it absorb whatever bass frequencies hit the soffit, especially if they hit the four foot deep (and four foot tall) section in the upper left front corner?

Does it matter that there is no mirror image soffit on the right side of the room descending from the ceiling above the right side wall?

AFFF1A64-1154-4A2F-81BE-95C32507BCB3.jpg
 

DaveyF

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Jul 31, 2010
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Ron, I believe that symmetrical is usually always better in regards to these matters. The fact that you have the height in your room is going to be the most positive thing about the design...vs. if you had a standard height ( 8') ceiling. More volume is also a plus.
Probably the ONLY way to really know the result of your design is to actually hear it once completed. Not the best answer, I know, but really the most logical, IMHO.
 

GaryProtein

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I would go for asymmetrical placement. Having two mirror image traps will only give more of the same response. Having them in asymmetrical locations will help smooth out the response and since the very low frequencies tend to be less directional asymmetrical traps will be better.

An slightly asymmetrical room, or one with a non-parallel wall will also smooth the bass response.
 

Ron Resnick

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In this hobby asymmetrical is rarely good, but I actually think you might be right in this case. Or it may be hopeful, wishful thinking on my part!

The bottom of the soffit is almost four feet above the top of the speakers. If there are any wayward low frequency waves up there hopefully the four foot deep box will absorb them like a black hole.
 

Bruce B

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Apr 25, 2010
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I use symmetrical, but at varying depths. Soffits on the sides are about 2’ deep and front soffit is about 4’ while soffit in rear is about 6’ deep.
 

sbo6

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I would go for asymmetrical placement. Having two mirror image traps will only give more of the same response. Having them in asymmetrical locations will help smooth out the response and since the very low frequencies tend to be less directional asymmetrical traps will be better.

An slightly asymmetrical room, or one with a non-parallel wall will also smooth the bass response.

X2..
 

ddk

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May 18, 2013
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Dear Ron,

Not sure if what you have is a bass trap, a trap for other frequencies or nothing at all. Absorbing below 100hz effectively is very difficult this is one area that requires complex measurements, IME most commercially sold so called bass traps are useless and nonlinear. You have BJs inside other walls that you're covering up with a hard wall, why not here? Is it not visible? I don’t have any experience with the type of trap you’re building here, don’t want to make any assumptions but best case it doesn’t do anything.

david

Do high-mounted or ceiling-mounted bass traps, when they are located well above the tops of the loudspeakers, have to be symmetrical on both sides of the room?

Imagine seven foot tall speakers in a listening room with a 15 foot tall ceiling. A large, hollow, wood-framed soffit descends four feet from the ceiling on the left side of the room (starting at the ceiling and continuing down from the ceiling for four feet on the left side wall). This soffit is six inches deep in some areas and four feet deep in the front left corner of the ceiling. The entire soffit, at each depth, is filled with blue jeans insulation. The front left corner section is four feet tall (like the entire soffit) but is four feet deep and filled entirely with blue jeans insulation.

The entire soffit is open to the blue jeans insulation; the soffit is not covered with drywall or any other solid or reflective material.

What effect will this large, acoustically-porous, sound-absorbing, high-located area have on the acoustics of the room?

Will it absorb whatever bass frequencies hit the soffit, especially if they hit the four foot deep (and four foot tall) section in the upper left front corner?

Does it matter that there is no mirror image soffit on the right side of the room descending from the ceiling above the right side wall?

View attachment 40598
 
Last edited:

dminches

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Oct 22, 2011
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Jeff Hedback designed my room and the front 4 ceiling-mounted base traps are symmetrical. The 3 behind that are not. This may be due to some room configuration constraints but I can tell you they did the job.
 

ddk

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May 18, 2013
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Jeff Hedback designed my room and the front 4 ceiling-mounted base traps are symmetrical. The 3 behind that are not. This may be due to some room configuration constraints but I can tell you they did the job.

Did you hear the room without the traps or this was done prior to putting the system in?

david
 

dminches

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Oct 22, 2011
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Did you hear the room prior to the trap installs or this was done prior to putting the system in?

david

I heard it prior which made this fun.

Before the treatments went it the room was like an echo chamber and listening was fatiguing. In addition, there was a horrible exaggeration at 41 Hz. After all the work was done the peak was gone and the room because a music haven.

Screenshot 2018-04-30 09.51.14.jpg
 

Rodney Gold

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Jan 29, 2014
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To absorb 60hz you need a flat trap of about 4ft spacing from the flat wall (1/4 wavelength of the freq ) and much thicker if you want to go below that ... I would rather use DSP and or a swarm of 4 subs to control bass below 100hz..
 

dminches

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Oct 22, 2011
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To absorb 60hz you need a flat trap of about 4ft thickness (1/4 wavelength of the freq ) and much thicker if you want to go below that ... I would rather use DSP and or a swarm of 4 subs to control bass below 100hz..

Well, I don't have 4 ft traps and the bass is controlled.

Doesn't using DSP require moving the signal through a digital process?
 

Bobvin

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Ron, what is Bonnie’s recomendation for this area of your room? No doubt bass energy that would enter this area will be absorbed by that depth of insulation but how that is experienced when listening is another matter.
 

Rodney Gold

Member
Jan 29, 2014
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It does require a digital process , but only for the low bass..you can run your main speakers unmolested and apply the dsp only on the subs or with pendragons , only on the bass towers
 

ddk

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May 18, 2013
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I heard it prior which made this fun.

Before the treatments went it the room was like an echo chamber and listening was fatiguing. In addition, there was a horrible exaggeration at 41 Hz. After all the work was done the peak was gone and the room because a music haven.

Sounds like you had additional work along with the traps done to the room?

david
 

ddk

Well-Known Member
May 18, 2013
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Utah
To absorb 60hz you need a flat trap of about 4ft spacing from the flat wall (1/4 wavelength of the freq ) and much thicker if you want to go below that ... I would rather use DSP and or a swarm of 4 subs to control bass below 100hz..

Hi Rodney,

Maybe acceptable in an all digital system but DSP of any kind in the chain is a nonstarter for us analog lovers, personally I wouldn't even go there (ie. additional digital processing) for my digital front end either.

david
 

dminches

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Oct 22, 2011
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Sounds like you had additional work along with the traps done to the room?

david

Yes. I will post a picture when I find a good one. I have "point of first reflection" diffusers on the side wall and ceiling. And there are other traps in the front corners. He did a really nice job. I love the way the room (doesn't) sound.
 

Ron Resnick

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Jan 24, 2015
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Ron, what is Bonnie’s recomendation for this area of your room? No doubt bass energy that would enter this area will be absorbed by that depth of insulation but how that is experienced when listening is another matter.

Bonnie tentatively is recommending that the 4’ deep, straight soffit and the shallower angled soffit be filled with blue jeans insulation and be covered only by fabric. She seems to think the assumetry is okay, and that whatever low frequencies these soffit sections absorb at the 9’ to 14.5’ elevation of the room is all to the good.
 

Ron Resnick

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Jan 24, 2015
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Hi Rodney,

Maybe acceptable in an all digital system but DSP of any kind in the chain is a nonstarter for us analog lovers, personally I wouldn't even go there (ie. additional digital processing) for my digital front end either.

david

+1
 

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