# Help me choose the best material to build acoustics panels...



## Diskohouse (Jun 2, 2011)

Hello,

I have read through many of the other DIY acoustic panel post, but I have not come across an answer to my question and was hoping someone could help me. 

I have been looking to make some DIY acoustic panels. OC 703 is not locally available, so to get it will include a shipping cost. I did some research in to locally available alternatives to OC brand. There is an insulation company that has Roxul available, but not the Rockboard. What they have available is the industrial board call RHT (http://www.roxul.com/industrial/products/roxul+rht®+40,+60,+80,+100,+-c12-+120 ), which is rigid, so it should be ideal for this project. I am listing the values below for this product along with the values for OC 703 and 705. I plan on using these for reflection points for now (possibly a cloud) and plan on building bass traps at a later time. My question is would there be any advantage of using the 3 inch of the RHT40 over the two inch, or would it be a waste? Or should I just use the RHT80 in two inch instead? The RHT80 is 8 pounds in density per square foot vs the RHT40 which is 4pounds per square foot I will be totally cover these panels with fabric and making a frame to sit on the back of the panel to allowing space between it and the wall, leaving the sides open for maximum absorption. These will be mounted on the wall and behind the soundstage. I have listed the values for RHT 40, 60 and 80, along with Owen Corning 703 and 705 values for comparison (also included Rockboard). I am also including the pricing that was given to me today in Boston. When building panels for reflection points, should I care about all the frequencies? Or just worry about highs? The RHT40 3” offers great performance, but I am not sure if it’s a waste for wall mounted panels. Based on these values and prices, what would you guys do/suggest? 

RHT40
CO-EFFICIENTS AT FREQUENCIES
Thickness 125 Hz 250 Hz 500 Hz 1000 Hz 2000 Hz 4000 Hz NRC
1.5” 0.15 0.47 0.98 1.06 1.02 1.02 0.90
2.0” 0.26 0.68 1.14 1.13 1.06 1.07 1.00
3.0” 0.62 1.03 1.20 1.10 1.08 1.10 1.10

RHT60
ASTM C 423
CO-EFFICIENTS AT FREQUENCIES
Thickness 125 Hz 250 Hz 500 Hz 1000 Hz 2000 Hz 4000 Hz NRC
1.5” 0.19 0.55 1.03 1.06 1.02 1.01 0.90
2.0” 0.26 0.71 1.14 1.09 1.04 1.03 1.00

RHT80
ASTM C 423
CO-EFFICIENTS AT FREQUENCIES
Thickness 125 Hz 250 Hz 500 Hz 1000 Hz 2000 Hz 4000 Hz NRC
1.5” 0.17 0.58 1.06 1.07 1.00 0.99 0.95
2.0” 0.39 0.84 1.08 1.01 1.02 1.01 1.00
3.0” 0.68 0.92 1.08 1.03 1.03 1.03 1.00
4.0” 1.00 0.95 1.06 1.04 1.06 1.08 1.05


Product Name lbs/ft3 125 Hz. 500 Hz. 1000 Hz. 4000 Hz. NRC 
Owens-Corning 703 2" 3 lb. 0.17 1.14 1.07 0.98 1.00 
Owens-Corning 703 4" 3 lb. 0.84 1.24 1.08 0.97 1.15 
Owens-Corning 705 2"6 lb. 0.16 1.02 1.01 0.99 0.95 
Roxul Rockboard 60 6 lb. 0.32 1.06 1.02 1.04 0.95
Roxul Rockboard 80 8 lb. 0.43 0.90 0.97 1.00 0.90 

Cost comparision:
RHT 40: 7 sheets of 2” $36.64 --- 5 sheets of 3” $37.37
RHT 80: 7 sheets of 2” $46.63 --- 5 sheets of 3” $47.56 – 3 sheets of 4” $39.97
Sheets are 24”x 48”

Thanks for the help!!
Links to the data sheets
http://www.roxul.com/files/RX-NA-EN/pdf/RHT40-3-10-09.pdf
http://www.roxul.com/files/RX-NA-EN/pdf/RHT60-4-12-10.pdf
http://www.roxul.com/files/RX-NA-EN/pdf/RHT80-3-30-10.pdf


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## Diskohouse (Jun 2, 2011)

I spent 10 minutes formatting those values...so they will in nice order..... :/


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## bpape (Sep 14, 2006)

RHT40 in 2" will be perfectly fine in those applications. If the cloud is overhead and not at reflections and you have a lower ceiling, you'll want at least 4" there.

The RHT40 can also be easily used for bass absorbers.

Bryan


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## Diskohouse (Jun 2, 2011)

Thank you for responding Bryan!! I am not sure what you mean by this sentence "If the cloud is overhead and not at reflections and you have a lower ceiling, you'll want at least 4" there." For the cloud you are suggesting using a 4" panel (such as two layers of RHT40?). What do you mean by "not at reflections"? My ceiling is fixed and it's 8 feet in height. I plan on placing the cloud about half-way between the sitting position and the main drivers....I do plan on conducting the mirror test to help with the placement. I have one row of seating (a futon). Would one panel be enough for a cloud (24"x48")? Or should I use two panels, side by side, length wise (24" X 96")? Thank you for the help and suggestions!!

~Jamie


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## bpape (Sep 14, 2006)

Reflections in most cases can be handled by 2" material pretty effectively. Those reflection points will all be between your seating and speakers. Over your head directly, in rooms 8' or less, you can have some modal problems which are better served with thicker material. The problem you run into sometimes though is that the cloud over your head is limited by the projector beam to the screen.

Bryan


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