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DIY acoustic room treatments


Rudy81

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I am about to start acoustically treating my listening room. I had previously added treatments, but want to do things with a little more care and with some measurements to document the effects.

First up, will be a set of 5 diffuser panels for the rear wall. I have built the panels based on this design: http://arqen.com/sound-diffusers/

Finished painting the panels today so will include a picture of one while it cures.

I will be building several absorbers for the first reflection points and adding super chunk absorbers to all four room corners.

Figured I'd keep track of the build on this thread in case anyone is interested.

I selected UltraTouch Denim insulation for the absorbers so I don't have to deal with fiberglass. I had worked with fiberglass before and it is a major pain to work with. It also made the absorber builds more difficult since I needed to ensure I din't have fiberglass fiber floating around in the room.

I picked the R30 insulation based on the available acoustic data and its thickness. This product looks perfect for the project. The R30 is supposed to be 8.5" thick, but I was aware based on other forums that even after it expands after unpacking, it does not quite meet the advertised thickness. Out of the bag, it is currently around 6".

My current plan is to use FR-701 material to cover the absorbers. The FR-701 comes from Guilfords of Maine.

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The only way I found to do it is to just bite the bullet and order the minimum quantity from Home Depot. It is a lot of material, 8 bags of 5 pieces each. I'm calculating I'll be using about 5 bags from my current plan. At least 4 panels for the side wall reflection points, 4 panels for a cloud and whatever it takes for the our super chunk corners. Then, I plan on making some 4 foot super chunk pieces for the wall/ceiling corners at the reflection points.

The denim insulation is way more user friendly than all the fiberglass or rock wool I have worked with. I researched it quite a bit and finally just purchased it.

The challenge will be cutting the material. I don't think it is as easy to cut as fiberglass.

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Where did you get the acoustic information on this stuff? I know I can do a Google search, but thought you might have it handy.

One thing I've always wanted to try is what they used in the S.N. Shure Theater at work:

http://www.thresholdacoustics.com/projects/s_n_shure_theatre/

On the side walls they put in all of these slats or angled boards or whatever you want to call them. I think putting absorption inside the slots and channeling the sound through a slot coming out the back (rather than reflecting back out the same hole) would offer a lot of attenuation of the side reflections. You get some redirection / diffusion effects from it too - while also keeping the reverberant stuff outta the absorption zone as well. I'll have to sketch up something because it's not quite apparent from the pictures what I'm thinking.

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Rudy,

Cool.... I so much want to do something similar in my 2 channel room. HT is in the family room so acoustic treatments are probably not forth coming there( Low WAF). But I've pretty much got open license in the basement 2 channel room. Looking forward to your further posts on this. I know from your previous threads there will be no lack of info.

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Rudy,

Cool.... I so much want to do something similar in my 2 channel room. HT is in the family room so acoustic treatments are probably not forth coming there( Low WAF). But I've pretty much got open license in the basement 2 channel room. Looking forward to your further posts on this. I know from your previous threads there will be no lack of info.

Yes, the WAF is an issue in a multi-use room, like a den. A dedicated listening or HT room, OTOH, is a wonderful thing.

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Oops, overlapping posts.....is R19 the same thing as R30? I'm a bit surprised by how much low frequency absorption there is versus the higher frequencies.

I'm also a bit confused....I thought absorption coefficients couldn't be greater than 1? (defined as incident sound over the reflected sound)

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Where did you get the acoustic information on this stuff? I know I can do a Google search, but thought you might have it handy.

One thing I've always wanted to try is what they used in the S.N. Shure Theater at work:

http://www.thresholdacoustics.com/projects/s_n_shure_theatre/

On the side walls they put in all of these slats or angled boards or whatever you want to call them. I think putting absorption inside the slots and channeling the sound through a slot coming out the back (rather than reflecting back out the same hole) would offer a lot of attenuation of the side reflections. You get some redirection / diffusion effects from it too - while also keeping the reverberant stuff outta the absorption zone as well. I'll have to sketch up something because it's not quite apparent from the pictures what I'm thinking.

Very interesting idea. I think I see what you are saying.

I found the information here: http://www.acousticalsurfaces.com/wall_insulation/ultratouch_acoustic_test.html?d=28

That site is full of interesting information on acoustics.

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Oops, overlapping posts.....is R19 the same thing as R30? I'm a bit surprised by how much low frequency absorption there is versus the higher frequencies.

I'm also a bit confused....I thought absorption coefficients couldn't be greater than 1? (defined as incident sound over the reflected sound)

I compared the results with Owens Corning 703 and this stuff is comparable and I think cheaper.

The reason the coefficients is greater than zero has to do with absorption during the test of the side surfaces vs. just the front. It is explained somewhere in the notes of the test or on that site. Good catch though. I noticed that as well and found the answer somewhere.

No, the R30 is thicker than the R19. R19 is supposed to fluff up to 5.5". The R30 is supposed to fluff up to 8".

I'll attach the UltraTouch details below.

ut-denim-insulation-brochure.pdf

Edited by Rudy81
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Rudy,

Cool.... I so much want to do something similar in my 2 channel room. HT is in the family room so acoustic treatments are probably not forth coming there( Low WAF). But I've pretty much got open license in the basement 2 channel room. Looking forward to your further posts on this. I know from your previous threads there will be no lack of info.

Yes, the WAF is an issue in a multi-use room, like a den. A dedicated listening or HT room, OTOH, is a wonderful thing.

What i did to deal with the WAF was to get some Japanese Silk and wrapped the acoustic panels in it. 100% WAF. In the new HT room I will be using solid colors that are very dark and then use the panels we already made and insert them into the wall panels we are making.

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Made a quick prototype.

Goals were to keep frame as light as possible, keep build cost down, provide ease of attachment for fabric and look good when complete. This is 1/2" plywood I had left over from the diffuser build. Frame seems reasonably strong, should provide a good surface to staple the fabric and is pretty light.

I did note that when stood up vertically, the denim insulation tends to sag a little (1") under its own weight.

Trap thickness is 6" .

I had contemplated using my router table to open the sides with oval slots to increase effectiveness and reduce weight a little more. However, after reading an article on the effectiveness of doing this, it seemed like a lot of work for very little payback.

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Edited by Rudy81
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Rudy,

Cool.... I so much want to do something similar in my 2 channel room. HT is in the family room so acoustic treatments are probably not forth coming there( Low WAF). But I've pretty much got open license in the basement 2 channel room. Looking forward to your further posts on this. I know from your previous threads there will be no lack of info.

Yes, the WAF is an issue in a multi-use room, like a den. A dedicated listening or HT room, OTOH, is a wonderful thing.

What i did to deal with the WAF was to get some Japanese Silk and wrapped the acoustic panels in it. 100% WAF. In the new HT room I will be using solid colors that are very dark and then use the panels we already made and insert them into the wall panels we are making.

Did you find silk that has a loose weave? I would think silk would tend to reflect high frequencies. I have to figure out what fabric to use. I will be using quite a bit, so am leaning toward Joann's speaker fabric. However, the FR701 from GOC is much nicer I think. I should get some samples in the mail today or tomorrow.

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I wonder what kind of effect the sagging will have. If any I wonder if cutting the panels of insulation in 2 with a small brace in between would help.

I will likely either glue or staple the top portion of the insulation to the top of the frame. My other option is to make the frame about 1" shorter. The nice thing now is that the frame is 48" which saves me having to make more cuts. Making the frame 47" is not a big deal, but I try to be as efficient as possible.

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Project update. Things are moving right along.

I decided to modify the frame from the initial prototype. I made 10 frames that are only 5" deep. This allows the insulation to give the finished trap a slightly rounded front and made it look more professional. Also, I added some paper to the back to keep the insulation from pushing out the back once the fabric was added.

I ordered the FR701 samples from GOM and went to Hancock's to see if I could match the material. I was fortunate enough to find a very close match in weave and weight to the FR701. Luckily, it was on sale for $7 a yard. At about $20+ a yard for the FR701, I couldn't pass it up. Granted, the fabric I got is not fire rated. However, not a big concern since the UltraTouch insulation is fire rated and this should not be an issue.

The end pieces of the frames are half of a french cleat which will hopefully make hanging the traps an easy proposition.

The project has been slow since I took slow approach to making the frames and finished traps as light as possible, yet sturdy and well built.

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Edited by Rudy81
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First up, will be a set of 5 diffuser panels for the rear wall. I have built the panels based on this design: http://arqen.com/sound-diffusers/ Finished painting the panels today so will include a picture of one while it cures.
Are those a QRD of some kind? I have a calculator that you can use to plug in the freq. you want to diffuse and it gives you all the pieces you need to cut and the order of placement.

I found some 2 inch balsa online, which would make them a lot lighter, but the cost was more than I wanted to spend.

Bruce

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Bruce, I don't think they are quadratic diffusers. I had made some of those previously and was not happy with that project due to size and weight of the finished product. The link I provided has a lot of information on that design. The design I built was the result of a study done for a thesis.

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