rockwool Low/high Density?

hi, About to order rockwool but have a question that I think warrents a new thread.. I have a 2 leaf studio planned and I am especially looking to stop low frequecies of drums.. (cyms too but I am hoping the mass will stop them.) In the uk the "best/most common" rockwool seem to be rocksilk, The product code represents the density and there are thicknesess of 50mm 60mm 75mm and 100mm Products are. RS33 RS45 RS60 am I correct in reading that my best solution would actually be low density (so cheaper RS33) but thicker so 100mm? also this will not be compressed as it will sit in the stud frame (thou I may have budget to fill the remaining "air" space with cheap "pink fluffy stuff".. please advise Thanks Geoff

Sounds like a plan. Remember the wool is to absorb energy within the air cavity (the total air space is INCL the wool within the frame). So placing wool with high absorption numbers is good. And yes, the cheap stuff will do. More airspace is better isolation, so wider wool will extend the air space indeed. Also compress the wool a little against the inner leaf (gypsum board) to prevent it from resonating too much. IF you can afford to go with 100mm, I'd do so. Transmission loss for low end is a much more difficult to achieve than mid/high (cymbals 'n stuff for example). By adding basstraps etc you'll lower the bass energy in a room. That means less low-end energy to isolate.