killing ceiling reflection

Hi guys I've got a quick and easy question for you. I have 8ft ceilings and I would like to keep as much height as possible for mic placement reasons, of course. I read that deadening the reflections bouncing off the ceiling is equal to having higher ceilings. If this is true would 2" 703, or an equivalent, suffice for killing the reflections thus giving an audible illusion of a higher ceiling or would it have to be much more dense to have a noticeable effect?

Higher density of the insulation won't help you any. Once you get up to around 48 kg/m3, it is diminishing returns. That's about optimum density. Higher than that, and you are just wasting money for no additional benefit. Unfortunately, 2 inches isn't enough to do what you want. You'd need at lest twice that, and probably more if you can. I think I'd go for 6 inches. Your problem, of course, is that you don't have much height to start with. Have you considered re-building your ceiling "inside-out"? That means that you would take the drywall off the bottom of the joists, and re-locate it to the top of the joists. I'm assuming that you have a proper fully decoupled two-leaf ceiling? If not, then there isn't much you can do. But if you do have a decoupled two-leaf, then moving the drywall from the bottom of the joists to the top will gain you all the space between the joists for acoustic treatment. That will be more than 3 inches (assuming you have 2x4 joists), and perhaps better than that, if you have 2x6 or bigger joists. "Inside out" is the best way to go for tight spaces, such as yours. But if you can't do that, then you'll just need to sacrifice some headroom, and put 6 inches or so of insulation (either rockwool or fiberglass) up there. That still won't make your ceiling "disappear" acoustically, but it will help to a certain extent. - Stuart -

alternatively you can build ceiling panels. Make an 8' x 4' (4' x 2' in smaller room) box of 4" x 3/4" and add a 1/2" plywood back to it. Fill the box with 4" insulation and wrap the whole thing with cloth stapled to the back. Then hang them from the ceiling with light chain from all 4 corners plus one in the middle and angle them to 12 degrees. Add as many as you need. It's the plywood (MDF) at the back that is going to break the floor ceiling standing waves so if you want it live leave out the box and the insulation ;) check the panels in the top left of this picture - they are 2' x 2' panels of MDF at differing angles.