Roxul RHT 40 4inch has sound absorption coefficients all above
1.oo for the standard frequencies. Is there any reason to use two inch boards rather than just using four inch. If I use four inch only the calc for sabins are fine across the board. 320 square feet of board delivered comes out to $332.!3 and I am calculating right around 500 sabins 125hz, through 4khz. Is there something I am missing?

It really is all going to depend on what is needed. But there is nothing wrong with using all 4" panels throughout the room. Small rooms can use as much bass control as possible.

Glenn

thank you for reply Bob

Bob?????????????

If you go with 2" panels the absorption will decrease at lower frequencies. I agree that there's nothing wrong with using 4" panels everywhere, though 2" panels will work just fine at first-reflection points.

I have been called worse.

Glenn