# DIY Bass trap this weekend project - Got a ?



## Talley

I'm going to break down and build two bass traps so I can test them out and see how they interact with my room. My plan right now is to build two corner traps 6 feet tall that will basically free stand and fit into the corner. I will build a frame like a windows box using 1x10 on all the sides around and I will use two layers of 4" rockwool. These are standard 24"x48"x4" 4lb density panels and will cut them to 18" in size. This is only because my space will not allow for a full 24" across diagonally in the corners so I need to chop it down to 18".

My simple question is this. Do I glue the two panels together for one solid 8" thick piece with an airgap behind them or should I place a small airgap between them of 1" isolating the panels form eachother using some furring strip material (green) See my image on my proposed idea.

What is more effective... solid 8" or having the airgap?


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## bpape

Don't bother gluing them but have all the thickness as far out as you can get and leave all the gap in the rear close to the corner.


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## Talley

bpape said:


> Don't bother gluing them but have all the thickness as far out as you can get and leave all the gap in the rear close to the corner.


Well that should make things easier lol. Thanks!


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## Tonto

I would use the cut off pieces to make a third row! I would piece them together on the back of the second layer (in between would be even better if you have enough) of Rockwool. 

I don't see the benefit of the 1x10's. What is your rational for that? I would expect them to reflect a portion of the bass wave negating the effect of the air gap which is very important. The depth of the air gap is what determines which part of the wave returns through the trap. Correct me if I'm wrong here! I'll be in the same boat soon.


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## NBPk402

When I made mine... I just cut triangles, and stacked them (floor to ceiling), and then made a 3/4x3/4" wood frame that I covered them with (fabric wrapped). You can just angle cut the wood frame if you want the corners to be flush with the frame...which is much easier IMO than trying to cut angles in the Rockboard.


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## Talley

Tonto said:


> I would use the cut off pieces to make a third row! I would piece them together on the back of the second layer (in between would be even better if you have enough) of Rockwool.
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> I don't see the benefit of the 1x10's. What is your rational for that? I would expect them to reflect a portion of the bass wave negating the effect of the air gap which is very important. The depth of the air gap is what determines which part of the wave returns through the trap. Correct me if I'm wrong here! I'll be in the same boat soon.


I'm making a stand alone bass trap that I can move around if need be. The 1x10 will just make it sturdy so it can stand upright by itself. I will have all sides wrapped in fabric. I don't think your following what I was thinking so I'll just post up photos this weekend of me making some.

Do I have enough?... I hope so  Place locally sells this much for $120 out the door


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## Talley

ellisr63 said:


> When I made mine... I just cut triangles, and stacked them (floor to ceiling), and then made a 3/4x3/4" wood frame that I covered them with (fabric wrapped). You can just angle cut the wood frame if you want the corners to be flush with the frame...which is much easier IMO than trying to cut angles in the Rockboard.


I need to be able to move it around. It's not a permanent dedicated room so if the occasion needed for me to move them then I must. anything on walls/ceiling is OK to leave but anything resting on floor needs to be able to move. I'll just do a simple box frame and wrap both sides with fabric just the same I did for my absorption panels. Just a single 6' tall 8" thick panel and have it placed in the corner and secured with some brackets.


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## NBPk402

Talley said:


> I'm making a stand alone bass trap that I can move around if need be. The 1x10 will just make it sturdy so it can stand upright by itself. I will have all sides wrapped in fabric. I don't think your following what I was thinking so I'll just post up photos this weekend of me making some.


I would use 3/4 x 3/4" wood and make a space frame...stuff it, and then cover with fabric....it will be much lighter. The old Tube Traps used to be made with round end caps, and a chicken coupe style wire wrapped in fabric...yours could be made similarly, but with a triangle shape and thin peaces of wood for support, hence the 3/4" suggestion.


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## Tonto

I'm with ellisr63, small, light frame. If you are worried about structural stability you could staple some small triangular pieces of something like 1/4" plywood in the corners of the frames. You could also build two 4ft traps & stack them. 

The bottom line is the performance of the absorption without losing the enhancement of the air gap. I'm hoping Bryan will chime in on his perspective as one of my corners will be portable as well. The back, right corner of my room has the door to my equipment room in the way! Thanks for sharing your build!


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## Talley

ellisr63 said:


> I would use 3/4 x 3/4" wood and make a space frame...stuff it, and then cover with fabric....it will be much lighter. The old Tube Traps used to be made with round end caps, and a chicken coupe style wire wrapped in fabric...yours could be made similarly, but with a triangle shape and thin peaces of wood for support, hence the 3/4" suggestion.


I wouldn't think the 3/4x3/4 would be strong enough. I bought some 1x3 material (3/4x2.5) that I was going to use. I may have to think about using some 1x2 instead. 1x2 furring strips are cheap like .70ea. frame would drop down to just a few dollars.

Well... I can always rip the 1x3 in half and get 3/4 x 1.25. Ya I'll probably do that since I already have the 1x3 plus I use the 1x3 for building the poly's which I need to make about 10 more poly panels to finish my ceiling

I think in the end my result will be poly's in the ceiling... qrd on side wall and along front wall but have a poly between the left main/center and righ main/center when listening to music and one poly at the main reflection on sidewall. Small 1'x2' QRD panels on the floor about 10 of those so I can lay them down for critical music and then pick them up for movie stuff. 

Tomorrow will be the bass trap build.


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## Talley

After measuring my space I find that it would be space prohibitive to build a frame. Therefore I will cut the pieces like the image below to maintain a 4" airgap and have 24" of face. I'll glue the pieces together to maintain rigidness and just glue some fabric to the sides. I want a flush look.

My rough math says this pattern after reusing the cut off portions would only take 2 of the 2'x4'x4" panels to make my desired 6' in height. OR I can use 3 pieces and this would yield me a 8' 4" tall panel or basically 8' w/ a tad left over. I'm minimizing waste and leaving an airgap and keeping the total thickness to 8" which is what I want to try first. I'll probably make these 24" tall and then I can just stack them. We'll see. 

either way no wood.


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## mtbdudex

Not sure if this will help you or not, I made these removable rear corner broadband bass traps:
*http://www.avsforum.com/forum/19-dedicated-theater-design-construction/1312693-diy-construction-methods-hang-able-acoustic-panels-moveable-corner-traps-not-fixed-frames-2.html#post19993984*

I cover the fronts with Kraft paper, as I don't need to over absorb the sonic energy from the room everywhere, so reflect the mids-highs back into the room







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wide rear view









recent close up, I use the shelf as a display of HT "stuff"









video clip showing they are moveable






Here's my front wall corner broadband bass traps also, minimum framing method








*http://www.avsforum.com/forum/19-dedicated-theater-design-construction/1312693-diy-construction-methods-hang-able-acoustic-panels-moveable-corner-traps-not-fixed-frames-4.html#post20588838*
From that thread


> A quick re-cap on my Front wall corner superchunk with "green" material, these were built 4/2011 thru 6/2011...slow but steady:
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> I did this as part of my front fabric mounting strategy as mid-support of the drywall corner edging and also just in case I ever wanted to tuck a sub there for whatever reason.
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> Post meet work, I realized the front wall speaker wires and side wall subwoofer coax needed to be moved....when building the HT I did not know about bass traps.
> Cut and re-locate to 29" from the corner....use scrap wood as backer....tape/mud/paint....everything takes time.....
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> Instead of making a fabric frame, I used drywall corner edge and wrapped the fabric behind that.
> Bend them from 90deg to 45deg by hand, went ok.
> Also, used kraft paper to reflect mid/hi freq like my other bass traps, just cut and tuck tight.
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> The fabric was cut with 4" extra top/bottom, and 2.5" each side.
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> Used plastic putty knife to tuck the sides.
> I designed the drywall edge to be 1/8" off the wall, and then tucked the fabric behind that and the cut triangles.
> A decent friction fit that stretched taught.
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> Done and absorbing some of those reflecting LFE!
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> This method was easy to do, an alternative to making the fabric frame and mounting that.
> Yes, I took measurements and will post them.
> 2nd row is almost deal flat across the LFE zone, 1st row not as good.
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> I also did freq listening of sub test tones with the RS db meter to grasp the chart to real life, a worthwhile thing to do, helps tie graphs to sound.


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## Talley

Built two panels.... 24" wide angle cut to sit flush with wall and 6 feet tall. Self supportive and just layed in the corner and a thumb tack to hold in place. Nothing fancy. 

Maybe I need to re-run Dirac now?

Overall it didn't really graph too much difference. Brought the entire decay down by about 2db is all. removed a couple of nulls at 100hz and 180hz by 12db... still a null but not such a dramatic peak. Soundstage has an airy feel to it but it's nothing dramatic.

I spent about 2hrs making them. Not sure if it was worth the effort. Maybe they weren't big enough? Seem to of made a differnce a tad at 16hz though which is weird. In the process I found a big tall vase in my room was a culprit of the 70hz ringing... it still rings at 70hz but it falls off now to 350ms instead of ringing STRONG like crazy forever. Need to fill that thing with insulation so it'll absorb at 70 .


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## NBPk402

Anytime you make changes to the room...you need to rerun your room tune software.:T


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## Talley

ellisr63 said:


> Anytime you make changes to the room...you need to rerun your room tune software.:T


Will do  Need to get the kids in bed first... need mo quiet.


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## albe

What a great thread! So informative, I made some bass tube traps, but I think I may tackle a couple of these...Thanks Talley!


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## Talley

Well I would do some more testing listening but I found out my firmware on the XMC was FW 2 and they have 3 so I decided to upgrade it last night and poof.... it bricked. Yay me.

or not.


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## NBPk402

Talley said:


> Well I would do some more testing listening but I found out my firmware on the XMC was FW 2 and they have 3 so I decided to upgrade it last night and poof.... it bricked. Yay me.
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> or not.


That is what I don't like about firmware updates... I had the same thing happen on a PS3 (luckily it was still under warranty). Hopefully yours is still covered. :T:T


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## Talley

ellisr63 said:


> That is what I don't like about firmware updates... I had the same thing happen on a PS3 (luckily it was still under warranty). Hopefully yours is still covered. :T:T


It is. I still have the Denon X4000 that has been boxed up since june that I never sent off for warranty.... I may limp on it if it decides to not suddently shut off all the time. I'm plagued with .

Sucks I was about to treat my front wall and ceiling and was going to use REW to find the sweet spots. I suppose that denon could work for me for now. Or I can use my office Denon cheapo just for applying treatments.

ya may just do that for the time being.


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## Talley

Correction: fixed the XMC. Figured out how to do a hard reset and gained control again and the second attempt worked so now on Fw 3.0. 

Glad that worked out. I'll rerun Dirac tomorrow and test again.


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## robbo266317

You have done a great job with those traps, have you noticed an improvement?


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## Talley

robbo266317 said:


> You have done a great job with those traps, have you noticed an improvement?


Thanks but really they were just thrown together real quick and wrapped with fabric just to contain the minwool fibers. IF I decide to keep them then I'll make a 3/4" frame for the front so the fabric is nice and tight and the frame could be screwed to the wall and give a cleaner look. Being self supportive they are a tad flimsy lol. But wanted to see if they worked. Total cost = $30 for the panels and some fabric about $40 total for two 6' tall panels. They clearly made "some" improvement but not sure if it was enough to justify the work. 

I can't say how much fully untill I redo the Dirac to see if there is any changes to that.

EDIT: You know after looking at the graphs I decided to to just match both before/after to determine the first 20db loss and compare. I was looking at 40db and unfortunately up till now I realized I had the input gain in windows set wrong so my max testing db was 90db which would cause conflicts with clipping... once I turned that down to 0db on the mic I can now test to 120db. I'm going to have to redo my tests but this is comparing a 20db down from initial playback level and compared a previous test to after. This shows a bigger picture.

I really need to retest and plan on doing that tonight. here is my initial findings:

(I can't really compare 40db down since I was not 40db higher than my noise floor. I will retest tonight with a 40db higher than noise floor and see the difference)


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## Talley

The spectrogram shows to be a huge improvement... but I also played the AFTER about 5db louder which I think the before graph is showing my noise floor.

Again... I need to re-test at 40db above noise floor.


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## Talley

And here is the FR

Again... I really need to do a better instantaneous side by side test to see the difference which is why I wanted to make the panels self supportive (within reason - a thumb tack to hold em in place) so I can do a before/after test quick and effortless.


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## Talley

OK... I found a subwoofer before/after that was the same db test a true before/after but on different days. I do know my furnace is what rings at 45hz so that is room noise. I can turn the a/c off and that hump is gone complately. Nothing I can do about it since I have non dedicated space. I need to make sure to turn everything off when I do my tests to help consistency.

You can see on these tests the difference was "subtle"


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## NBPk402

Talley said:


> They clearly made "some" improvement but not sure if it was enough to justify the work.


In my opinion any amount you can do is better than none...plus it makes it easier on the Dirac to tune the room. :T:T


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## Talley

ellisr63 said:


> In my opinion any amount you can do is better than none...plus it makes it easier on the Dirac to tune the room. :T:T


True. I didn't think of that really. Even if it only helped a couple of db like 2 at the most then thats 2 less that Dirac has to work out. Less stress in essence. 

I don't have the room to do diagonals in the back of the room corners but I could do some 18"x8"x40" chunks. Not sure if that would help but I could try that too. They would have to fit flush into the corners like this:


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