# Some Advice on my Acoustic Treatment Approach



## hendry_2002 (Dec 30, 2014)

I have been reading a lot and i mean a lot of stuff about acoustic treatment, and i am pretty much got the complete idea on how to treat such HT. However, some advice from experts is really appreciated to clear some confusion in my understanding.

1- I know fiberglass 703 2" is properly one of the best material for building acoustic panels for early reflection spots (side walls), however, due to health issue, I have very sensitive skin, which can be irritated easily by such material, so i don't want to take the risk at all (even though it will be covered by fabrics), because i have experienced pretty bad nights after getting exposed to OC 703 during the soundproofing phase in my HT.

I have seen many forums about people wrapping fiberglass with pretty thin plastic, and then place some 1" foam for HF frequencies as the plastic might reflect those frequencies! 

will this work? have you experienced such approach? or i can just place some foam directly over the fiberglass and cover the whole thing with GoM fabric? which approach better in terms of sound and health concerns.

2- since I am planning to have my complete HT covered by panels (GoM FR701 fabrics), some areas will have actual treatment such as fiberglass or diffusers, and some obviously will be empty, so what do you suggest i put inside those empty panels? because i cannot keep them empty especially those panels will be 3" in depth. maybe place Fiberglass FRK face towards my HT?! 

I apologize if my questions have been addresses here before, but to be honest i have searched already and could not find something that's addressing my concerns exactly.

3- my rear wall will be approx. 9-10 ft away from my sweet spot, so do you suggest to have it completely covered by 2" absorption panels or a mix with diffusers? does the distance actually matter for the rear wall from your sweet spot?

note that my 7.2 HT dimensions has the following measures: 26' Depth x 15.5' Width x 10' H

Thank you in advance,


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## bpape (Sep 14, 2006)

Most people who show sensitivity are sensitive to the chemicals in the binding agents that hold the fiberglass together such as phenols and formaldehyde. You can purchase products that are still fiberglass but do not have those such as the ECOSE materials. 

If choose not to and you use plastic, get it as thin as you can. The lighter the material, the higher in frequency it will start to reflect.

Why can't they stay empty? If you prefer not, just put a plywood face on them and fill with regular insulation to keep them from resonating. 

For the rear wall, think much thicker and with a heavier membrane as most problems off the rear wall tend to be lower in frequency but you want to keep the surround field more lively.


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## hendry_2002 (Dec 30, 2014)

bpape said:


> Most people who show sensitivity are sensitive to the chemicals in the binding agents that hold the fiberglass together such as phenols and formaldehyde. You can purchase products that are still fiberglass but do not have those such as the ECOSE materials.
> 
> If choose not to and you use plastic, get it as thin as you can. The lighter the material, the higher in frequency it will start to reflect.
> 
> ...


Thanks for your advice,

so the approach with very thin plastic is valid then, so should i add 1" acoustic foam infront of the plastic to absorb HF? and when you said very thin, we are talking about 1 to 3 max mil right?

As for the rear wall, could you explain by what you mean with a heavier membrane? btw my english is not my first language


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## bpape (Sep 14, 2006)

Mass loaded vinyl works well but is expensive. Pond liner will allow a bit more mid to be absorbed but is cheaper.

You can add foam to the front if desired but not really necessary if you use very light plastic as you stated.


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## hendry_2002 (Dec 30, 2014)

bpape said:


> Mass loaded vinyl works well but is expensive. Pond liner will allow a bit more mid to be absorbed but is cheaper.
> 
> You can add foam to the front if desired but not really necessary if you use very light plastic as you stated.


Mass loaded vinyl to be placed in the rear wall covering thick fiberglass panels? right?

so it reflects HF/MF & and absorbs LF?


btw, you mentioned that i should fill regular insulation in those empty panels which will be covered by plywood to avoid resonating, i am planing to have wall closet inside my HT, will this affect my overall acoustic treatment? because i have a concrete column in the middle of my room, about 3 feet in depth, so i will cover this columns from the front to the back of my room with a partition "drywall/wood", and utilize this area as AV rack, and store. any thing i should keep in mind?


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## bpape (Sep 14, 2006)

Any time you create a cavity you want to damp it. 

The MLV at 1/2 lb will cut off around 300Hz or so. But you have to have it in front of and touching a denser insulation like OC703 or 3lb ECOSE. So its a damped membrane, not a live one like a drum head.


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