First I am not going to go all out to decouple the Theater from the rest of the house. I am not to concerned about the sound problems. 3 Walls of the theater are concrete, the 4th wall is common to other rooms of the house. Ceiling has to be suspended to allow access to things in the floor system.

The rest of my house I did in Dense Pack Cellulose for insuation value, but from what I read it is suppose to be better for sound also.

So my question is if I should Dense Pack the walls of you regular fiberglass batts. Also for the rear riser and stage would dense pack work to fill them up with?

Dense pack is not at all what we want if building a full blown isolation room. You indicated you are not concerned about this so it really doesn't matter either way.

Dense pack is not at all what we want if building a full blown isolation room. You indicated you are not concerned about this so it really doesn't matter either way.

I thought the higher mass of the dense pack would be better then the light fiberglass but I could be wrong. I know I am not doing a perfect sound control room but I was to use the best material in what I am doing. I am not going to waste me time doing dense pack if a regular R13 fiberglass batt will be as good.

Denser is often desired for open-air absorption. Like if you were making panels or traps. For in-wall or in-ceiling enclosed application, you want the less dense material.

Given that you essentially still have an open joist system after the suspended ceiling, the dense pack might work better for you. If you were drywalling the ceiling, you would want the lower density materials.