Roxul RHT 120 - anyone using?

[Sha-Zam]

Tech specs can be found Here. At 12lbs/cf I would think this stuff would be el-fantabulous for bass trapping... well if using 4" or 6" thickness anyway. There seems to be some suggestion about a turning point though, like if density is a continuum between "cotton candy" and "rock", at some point more dense is less desirable for sound absorption. How about 12lbs/cf? Good? Bad? Ugly?

[slowjett]

Originally Posted by Sha-Zam

Tech specs can be found Here. At 12lbs/cf I would think this stuff would be el-fantabulous for bass trapping... well if using 4" or 6" thickness anyway. There seems to be some suggestion about a turning point though, like if density is a continuum between "cotton candy" and "rock", at some point more dense is less desirable for sound absorption. How about 12lbs/cf? Good? Bad? Ugly?

Sounds heavy to me but what do I know. I've got a bunch of Dow SafeTouch here I think its probably 2lb/cf but I dont know how to tell can not find specs.

[Glenn Kuras]

Originally Posted by Sha-Zam

Tech specs can be found Here. At 12lbs/cf I would think this stuff would be el-fantabulous for bass trapping... well if using 4" or 6" thickness anyway. There seems to be some suggestion about a turning point though, like if density is a continuum between "cotton candy" and "rock", at some point more dense is less desirable for sound absorption. How about 12lbs/cf? Good? Bad? Ugly?

I have never tested 12 pound but it should work fine. If I was you go with 3 to 8 pound.

[avare]

Originally Posted by Sha-Zam

Tech specs can be found Here. At 12lbs/cf I would think this stuff would be el-fantabulous for bass trapping... well if using 4" or 6" thickness anyway.

Bas traps require lighter material if filled completely. At 4" thickness 3lb/ft^3 is about ideal. For 6" use 3lb/ft^3 or slighter lighter. Those are suggestions for fiberglass. For mineral wool use 4lb/ft^3 as a starting point.

Andre

[Sha-Zam]

Andre, thanks for your recommendations. I've just finished reading some of your comments about gas flow resistivity in other threads, and about how density does not equate to absorption but gas flow resistivity together with thickness does. That makes a lot of sense considering that sound waves consist of alternating variances of pressure. For low bass, say in the sub-80 hz range, what kind of thicknesses are we talking about for 3lb/cf fiberglass to achieve an absorption co-efficient of 1?

[avare]

Originally Posted by Sha-Zam

For low bass, say in the sub-80 hz range, what kind of thicknesses are we talking about for 3lb/cf fiberglass to achieve an absorption co-efficient of 1?

A deceptive question.

If I was designing a broad band absorber to be effective down to 80 Hz using 3lb/ft^3 fiberglass, I would use 4" thick with a 6" gap behind it. If I was not restricted by material, I would use regular insulation 10" thick. It is cheaper with the same acoustic performance.

If I was doing a "fun" project for myself or someone working with found space and it had the space, I would do 16" thick with regular insulation.

Andre