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RFZ Broadband Absorber With 32kg/m3 Rockwool
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alecamp
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#1
19th February 2013
Old 19th February 2013
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RFZ Broadband Absorber With 32kg/m3 Rockwool

Hi, friends.

If I´m going to build 4" thick broadband absorbers to put on the reflection points, can I use 32kg/m3 rockwool or should it be denser?
Building it with 48kg/m3 rockwool would make significant difference?


Thanks
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19th February 2013
Old 19th February 2013
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Quote:
Originally Posted by alecamp View Post
Hi, friends.

If I´m going to build 4" thick broadband absorbers to put on the reflection points, can I use 32kg/m3 rockwool or should it be denser?
Building it with 48kg/m3 rockwool would make significant difference?


Thanks
At 4" thickness, 64 kg/m³ is about optimum. The lighter material will provide less low end absorption. Some people companies user denser material due to handling ease. The difference is not major. If you are going to order the material, why not order the better stuff?

Densely,
Andre
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18th December 2013
Old 18th December 2013
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Bumping for the brazilian fellow countrymen.

Came across some rockwool pannels and the specs rate the 32 and the 64 kg/m3 pretty much the same @ 125Hz. I know that's "on paper" and it has some bias (from the manufacturer)...and from what I read here Gas Flow Resistivity is a better measure.....right?

Thanks in advance,

Cheers!
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18th December 2013
Old 18th December 2013
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I am using 32kg/m3. Would I get better results at 64kg/m3? Probably. But it seems to do the job for me. As said above, wouldn't sweat the difference too much.

I can tell you on thing that is worth sweating though. These things can be reflective at around 1khz. By angling them slightly, and I mean slightly, I got a drop of 15-20db in various places at 1khz within 20 ms. THAT is worth mucking around with. Something to keep in mind when you get to futzing around with REW.
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18th December 2013
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Quote:
Originally Posted by dodittydada View Post
I am using 32kg/m3. Would I get better results at 64kg/m3? Probably. But it seems to do the job for me. As said above, wouldn't sweat the difference too much.

I can tell you on thing that is worth sweating though. These things can be reflective at around 1khz. By angling them slightly, and I mean slightly, I got a drop of 15-20db in various places at 1khz within 20 ms. THAT is worth mucking around with. Something to keep in mind when you get to futzing around with REW.
Interesting. I'll watch for that.

Does rigid fiber glass also "suffer" from the same issue? Because that's the first time I see someone bringing this up.
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18th December 2013
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Yes it does, or maybe "can" is the best answer. What you cover it with would also have an effect. I am using rigid fiberglass with burlap covering. I tested it myself with REW so I know it to be a fact. That stuff dosent perfectly absorb right across the range, and in fact is reflective around 1K in my case. Also a little at 4k and 8k, but much less significant there.
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18th December 2013
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+1

This is the very reason why rooms with tight dimensions are difficult to treat. I recommend covering reflection-point panels or trapping with a high-quality acoustic foam.

Cheers,
John
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19th December 2013
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Great - thanks guys.
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