Help In Building Acoustic Panel

I am wanting to build several acoustic panels for my drum platform which is 7'x8'. Due to the design I have limited space for my ceiling panels. In a nutshell I only have 3 1/2" to work with. QUESTION IS... Do I build a panel with: 1. 3" of Rockwool with 1/2" air gap or 2. 2" of Rockwool with 1 1/2" of air gap What is better - an extra inch of air gap or extra inch of mineral wool? Thank you

Personally, I'd go with more rockwool and less air gap. Others might disagree, but I'd go for the maximum absorption you can get if you have limited space. Especially over drums! - Stuart -

Thank you.