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Discussion Starter · #1 ·
Hi all,

I've got a home theater contruction build going here and I had specific question on acoustics. The room is 34'x15.9'x7.4' I'd like to create 4 superchunk bass traps for each corner. The question is this: What's the best location for the subs? Is it best to build a shelf and put the sub tight in the corner (assume I'm going to eventually have 1 sub in every corner) or should I have the sub diagonal across the face of the superchunk trap and have the trap extend floor to ceiling?

The subs are 40" tall, CHT 18.2 subs. I ruled out midwall placement because I'm trying to hide the subs behind curtainwalls.

Would love some recommendations on how best to place the subs with corner bass traps.
 

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Corners give the most sheer output but also normally maximally excite your room modes. Center of walls is actually best if multiple subs. Another option is deliberately non-symmetric to not excite the room reflections in the same way or at the same frequencies. Iterative trial and error is the best way to go about this. Get one dialed in to your mains. Then bring the other into the equation and try to compensate for any anomalies from the first sub by creating offsetting response issues from the other.

Bryan
 

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Discussion Starter · #3 ·
So you'd advise giving up the corner loading? I'm fairly limited in placement. I have 4.5 feet behind the front screen that I can place the sub/subs and 3.5 feet behind the back cloth wall that I can put subs so I guess the best bet will be to do centers front and back wall and start measuring. I was hoping to try to get a bit of extra umph out of the corners (they are backed by concrete) to help me bump up the super low fequencies (under 10hz). How much would I lose there going centerwall do ya think?
 

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I would suggest that you build your bass traps floor to ceiling (at least for the front wall) and initially place your main sub right next to the trap..That way you still get a bit of reinforcement from near corner location..
If it's too boomy there, then you can gradually slide it towards the centre location and take measurements as you go to find the best position..
 

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Discussion Starter · #5 ·
Thanks all. I'll start with the centers and test out the best placement. Will start building out the corner traps tommorow. I've read that the less dense pink stuff is better for large corner traps so I'm using r38 in a 2'x2' triangle.
 

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Discussion Starter · #6 ·
Another question about the sidewalls. I've seen a bit of debate about how to treat the sidewalls. If I wanted to use Linacoustic or something similar up to 42-44" from the floor, do you mount that with the lining facing out to reflect the higher frequencies or insulation facing out to absorb everything?
 

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The lining of the linacoustic is pretty thin. It will still absorb mostly all the way up even with the facing out. If you want it full all the way up, then put the lining against the wall.

Personally, I don't care for the linacoustic. It's just too thin to do much of anything. I don't like to use anything less than 2".

Bryan
 

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Discussion Starter · #8 ·
Thanks for the feedback Bryan. Instead of Linacoustic what do you trypically recommend. I'm trying to avoid a bunch of large panels on the sidewalls for asctetics if it can be helped. Is there other material out there that is better or is it purely a function of depth? How much performance do you lose by using 1" material vs 2"?
 

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1" vs 2" is purely a matter of how low in frequency it will be effective. You can still hide 2" 703 or equivalent behind cloth walls just like the linacoustic. You just need to fir it out farther.

Bryan
 

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Discussion Starter · #10 ·
Thanks Bryan. I'm gonna have to figure out how to deal with a 2 inch bump out. I was planning on leaving the top half of the wall painted sheetrock.

Can I ask a question about diffusion? I've read a ton of theads about diffusion and have seen some of the debates about how close is too close to sit to a diffusor. I've been looking at the GIK QRD diffusors, and wondered what the minimum seating distances would be. My back row would be about 3 1/2 feet away, and the middle row would be 10 feet away. Is that too close to the diffusors along a rear wall? Also, do you recommend putting diffusors along the side walls towards the back of the room?
 

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How far you sit from a diffuser is a function of the wavelength of the lowest frequency a diffuser will work on. 3.5' is a bit close. We usually recommend 5' minimum but technically it's more like 4.5'

On the rear portion of the side walls, that might work OK. Usually the back wall of a home theater is better off with thick bass absorption than diffusion.

Bryan
 

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Sorry this is not an acoustical response, but I was wondering about the desire to leave the top portion painted sheetrock. I was thinking that when sidewalls are treated, the closer you are to the speaker, the higher up the wall the treatment goes. As you go toward the back wall, the treatment diminishes to next to nothing.

If this is the case, I would think that would create a "ladder" effect on your painted walls that might not look like you want. Perhaps Bryan can set me straight on this one.......
 

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Actually, we would do more higher up in the front portion of the room and then drop it down outside the reflection zone on the sides to leave the surround field a bit more lively.

Bryan
 

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Discussion Starter · #14 ·
I had planned to ladder up the absorption to match the riser height. Is this not a good idea? For the rear, I have some 242 traps, are they good enough or so I need monster traps?
 

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Just make sure you cover the reflection level the entire way. In the rear, Monsters would be far preferable to 242's.

Bryan
 

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Discussion Starter · #16 ·
ok cool, I'll do that. I was originally going to use a fabric mountain system like Wallmate, but they only support 1 inch panels. Anyone know of a fabric mountain system that supports 2 inchs?
 

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Just fir out the 1" channel a bit and you can use the same stuff.

Bryan
 

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Hi all,

I've got a home theater contruction build going here and I had specific question on acoustics. The room is 34'x15.9'x7.4' I'd like to create 4 superchunk bass traps for each corner. The question is this: What's the best location for the subs? Is it best to build a shelf and put the sub tight in the corner (assume I'm going to eventually have 1 sub in every corner) or should I have the sub diagonal across the face of the superchunk trap and have the trap extend floor to ceiling?

The subs are 40" tall, CHT 18.2 subs. I ruled out midwall placement because I'm trying to hide the subs behind curtainwalls.

Would love some recommendations on how best to place the subs with corner bass traps.
Do you have a sub floor or basement? I am thinking of installing my next subs under the floor and having floor grills for the bass to travel through. By going this route it is out of site... which works for me.
 

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Discussion Starter · #19 ·
No, this is actually in the basement with concrete flooring. I'm building 2 false walls covered in fabric in front for my screen wall and in back to hide my rear subs, back surrounds, equipment rack and any rear wall absorption. Rear rear false wall also gave me the ability to keet the seating I the 60-80% zone and off te back wall.
 

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Discussion Starter · #20 ·
Yet another acoustics question:

I've been looking for the best, most absorbative carpet underlay and I've come to the conclusion that Jute fiber is the best for sound absorbtion. I realize it's nowhere near as good as what I'll get from fiberglass or rockwool, but this 40 ouch jute underlay looks promising:

http://www.rugpadcorner.com/superior-felt-jute-rug-pads.aspx?page=2

Bryan and Prof, would this stuff be worth the money to help tame some of the reflection from the floor? I plan to do some panels on the ceiling as well ar the first reflection point. My speakers are the Abbeys from Earl Geddes, and while they do a decent job controlling the horizonal directivity, their vertical CD based on the polar plots isn't quite as good so I'd love to be able to tame the reflections vertically as much as possible.

So the question is, it a pad like this worth the extra money?
 
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