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Discussion Starter #1
Hi guys. I start to build bass traps, this is what I have found to use as dampening material, the lowest of the curves are for the "extra bass" with total depth of 200 mm.
bassfelle 004.jpg

Master_A_abs1.gif
 

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Ummm. You do realize that the lowest curves are the worst performance, right? The rolloff at the top is likely due to a facing like FSK on it. 0.45 for 200mm (8" thick) is really really bad. With that thickness and the proper density, you should be up around .8 even down into the 60's

Bryan
 

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Discussion Starter #3 (Edited)
Ummm. You do realize that the lowest curves are the worst performance, right? The rolloff at the top is likely due to a facing like FSK on it. 0.45 for 200mm (8" thick) is really really bad. With that thickness and the proper density, you should be up around .8 even down into the 60's

Bryan
Hi Bryan. I must correct a bit, the curve is 100 mm damping material and 100 mm air behind it "A" mont.
What is proper density for a bass trap.
lglura
 

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That's still not all that great for 4" even flat on a wall, much less with a 4" space behind it.

Density depends on thickness. For a 4" panel, you can go anywhere from 2.5-6lbs/cu ft.

Bryan
 

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Discussion Starter #5
That's still not all that great for 4" even flat on a wall, much less with a 4" space behind it.

Density depends on thickness. For a 4" panel, you can go anywhere from 2.5-6lbs/cu ft.

Bryan
Thanks bryan, I will check with the supplier, what damping material would you recommend for bass trap

lglura
 

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I poked around a bit. What you've pictured is a ceiling tile product. also, the good absorption in the graph (top one) is for both the master and the xtra bass together and with a 200mm total system thickness -though they never say that I could find, how thick the absorption itself is.

This appears to be very very similar to the mineral wool we get here in the US.


http://www.knaufinsulation.co.uk/products/rocksilk_slabs/rocksilk_universal_slab.aspx

While they don't provide acoustic numbers, you can pretty closely follow these numbers.

Product thickness density 125hz 250hz 500hz 1000hz 2000hz 4000hz NRC
MinWool-1200 Industrial Board 1240 1.5" (38mm) 4 pcf (64 kg/m^3) 0.13 0.48 1.02 1.08 1.02 1.01 0.90
MinWool-1200 Industrial Board 1240 2" (51mm) 4 pcf (64 kg/m^3) 0.20 0.61 1.07 1.06 1.04 1.07 0.95
MinWool-1200 Industrial Board 1240 4" (102mm) 4 pcf (64 kg/m^3) 0.88 1.14 1.17 1.08 1.06 1.10 1.10
MinWool-1200 Industrial Board 1240 6" (152mm) 4 pcf (64 kg/m^3) 0.32 1.14 1.11 1.09 1.06 1.07 1.10
MinWool-1200 Industrial Board 1260 1.5" (38mm) 6 pcf (96 kg/m^3) 0.18 0.62 1.08 1.08 1.03 1.07 0.95
MinWool-1200 Industrial Board 1260 2" (51mm) 6 pcf (96 kg/m^3) 0.25 0.85 1.15 1.10 1.04 1.06 1.05
MinWool-1200 Industrial Board 1260 3" (76mm) 6 pcf (96 kg/m^3) 0.80 1.07 1.11 0.99 0.98 0.96 1.05
MinWool-1200 Industrial Board 1260 4" (102mm) 6 pcf (96 kg/m^3) 0.99 1.01 1.10 1.03 1.03 1.05 1.05
MinWool-1200 Industrial Board 1280 1.5" (38mm) 8 pcf (128 kg/m^3) 0.13 0.64 1.08 1.08 1.04 1.07 0.95
MinWool-1200 Industrial Board 1280 2" (51mm) 8 pcf (128 kg/m^3) 0.32 0.90 1.11 1.07 1.01 1.05 1.00
MinWool-1200 Industrial Board 1280 4" (102mm) 8 pcf (128 kg/m^3) 1.11 0.91 1.03 1.03 1.06 1.07 1.00
 

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I believe that's a typo in the table. 6" will definitely outperform 4".

Also, all of those numbers are pure A mount, flat on the wall, no air gap.

Bryan
 

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Discussion Starter #9
I poked around a bit. What you've pictured is a ceiling tile product. also, the good absorption in the graph (top one) is for both the master and the xtra bass together and with a 200mm total system thickness -though they never say that I could find, how thick the absorption itself is.

This appears to be very very similar to the mineral wool we get here in the US.


http://www.knaufinsulation.co.uk/products/rocksilk_slabs/rocksilk_universal_slab.aspx

While they don't provide acoustic numbers, you can pretty closely follow these numbers.

Product thickness density 125hz 250hz 500hz 1000hz 2000hz 4000hz NRC
MinWool-1200 Industrial Board 1240 1.5" (38mm) 4 pcf (64 kg/m^3) 0.13 0.48 1.02 1.08 1.02 1.01 0.90
MinWool-1200 Industrial Board 1240 2" (51mm) 4 pcf (64 kg/m^3) 0.20 0.61 1.07 1.06 1.04 1.07 0.95
MinWool-1200 Industrial Board 1240 4" (102mm) 4 pcf (64 kg/m^3) 0.88 1.14 1.17 1.08 1.06 1.10 1.10
MinWool-1200 Industrial Board 1240 6" (152mm) 4 pcf (64 kg/m^3) 0.32 1.14 1.11 1.09 1.06 1.07 1.10
MinWool-1200 Industrial Board 1260 1.5" (38mm) 6 pcf (96 kg/m^3) 0.18 0.62 1.08 1.08 1.03 1.07 0.95
MinWool-1200 Industrial Board 1260 2" (51mm) 6 pcf (96 kg/m^3) 0.25 0.85 1.15 1.10 1.04 1.06 1.05
MinWool-1200 Industrial Board 1260 3" (76mm) 6 pcf (96 kg/m^3) 0.80 1.07 1.11 0.99 0.98 0.96 1.05
MinWool-1200 Industrial Board 1260 4" (102mm) 6 pcf (96 kg/m^3) 0.99 1.01 1.10 1.03 1.03 1.05 1.05
MinWool-1200 Industrial Board 1280 1.5" (38mm) 8 pcf (128 kg/m^3) 0.13 0.64 1.08 1.08 1.04 1.07 0.95
MinWool-1200 Industrial Board 1280 2" (51mm) 8 pcf (128 kg/m^3) 0.32 0.90 1.11 1.07 1.01 1.05 1.00
MinWool-1200 Industrial Board 1280 4" (102mm) 8 pcf (128 kg/m^3) 1.11 0.91 1.03 1.03 1.06 1.07 1.00
Hi Bryan. If I understand correctly, a higher density in dampening material would be a better solution for a bass trap. In Norway we have a simular brand to Rocksilk Acoustic Floor Slab, but only in 50 mm thickness. How thick should I build panels, and what if i mix different material in the basstraps. how it will function as broadband bass trap?
 

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If you can only swing 4" thick, then the higher density would work slightly better for bass control. If you can do 6" or more thickness, you can get by with the 4lb density just fine.

Bryan
 
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