Mineral (rockwool) versus Cellulose Insulation?

[scuppari]

My primary concern is sound isolation... keeping sound from escaping the live room.

I've read density and dead-air are the two keys to isolation, but, it's my understaning "density" is most most important when trying to isolate lower freq. such as bass or drums. Is this correct?

If so, which type of insulation would be best suited for my needs.... Blown-in cellulose or Mineral (rockwool)? Or, should I use a combination of the two (Cellulose in ceiling cavity and rockwool in walls)?

Any STC comparisons of the two at lower freq's?

BTW-I've also been told to stay away from regular fiberglass b/c of lower isolation properties... is this also correct?

[knightfly]

I haven't seen any specs on the blown in Cellulose, but if it is lighter than the rockwool it should not be as good at lower frequencies. Spun fiberglas insulation (lightweight also) has little effect at lower freq's unless you are using it in a bass trap, and even then heavier is better for lower freq's, such as 703 or equivalent... Steve