I have been comparing a local product to imported Rockwool and after speaking to a insulation wholesaler here I am slightly worryed about the bass frequencies.
The local product is .50 at 125htz
Rockwool RW3 is .40 at 125htz
Roxul RXL80 is .75 at 125htz
He is saying 75mm rockwool is will absorb bass frequencies alot better but they all look similar to me. (except the price!!)
Could someone comment please, I suppose I am freaking out that I will spend $750 on insulation that will do a piss poor job at stopping my kick drum at full steam!!!
Thanks
JohnG
Insulation Question again!!
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JohnGardner
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knightfly
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If this is inside a wall, stop sweating and buy the cheapest 2.5 to 3 PCF (40 to 50 kG/cubic meter) rockwool, slag wool, sheep wool, rigid fiberglass, etc, that you can find - you'll likely not be able to tell the difference other than the finished weight of your wallet 
If this is for absorbers, be aware that these tests are so flighty and un-repeatable that the exact same materials tested on different days won't test the same most of the time - for this application, if you can get any test pieces of similar density, blow through them and see which is easier - it's likely this one has lower gas flow resistivity, so will work better at non-perpendicular incidences (which are by far the majority in a studio)
If you can't get samples, and the difference at lower frequencies is greater than maybe .2, you might want to go for the higher number. Even this can be tricky, because of the variations in testing means such as whether the sample was the full size of 8 x 9 feet, whether the edges were masked for the test, and probably a dozen other variables.
As long as you stay away from the lightweight house insulation for acoustic treatment you should be fine; it's more important to keep several inches of space behind the stuff so you get better absorption at lower frequencies. Otherwise the stuff just takes the "shine" off and leaves the room sounding muddy... Steve
If this is for absorbers, be aware that these tests are so flighty and un-repeatable that the exact same materials tested on different days won't test the same most of the time - for this application, if you can get any test pieces of similar density, blow through them and see which is easier - it's likely this one has lower gas flow resistivity, so will work better at non-perpendicular incidences (which are by far the majority in a studio)
If you can't get samples, and the difference at lower frequencies is greater than maybe .2, you might want to go for the higher number. Even this can be tricky, because of the variations in testing means such as whether the sample was the full size of 8 x 9 feet, whether the edges were masked for the test, and probably a dozen other variables.
As long as you stay away from the lightweight house insulation for acoustic treatment you should be fine; it's more important to keep several inches of space behind the stuff so you get better absorption at lower frequencies. Otherwise the stuff just takes the "shine" off and leaves the room sounding muddy... Steve
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JohnGardner
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