thealexdexter wrote:
I’m thinking that airspace is too small, but I have no idea what it should be.
Crutchfield used to have a calculator that would tell you the volume you need for various speaker types. If that is no longer there, you should be able to find it on the Web somewhere. Just look for speaker enclosure design calculators. A long throw speaker will give you better bass response but will need more volume in a sealed enclosure. Theoretically, you could put another hole in the ceiling and cover it with about a 2" speaker cover, like you would use on a tweeter, and then tunnel through the styrofoam to connect it to the space behind the 6X9 to create a ported system. Of course the tunnel would have to be just the right cross section and length to avoid nasty resonances. That's why acoustical engineers get paid the big bucks.
I have 4 6" long throw speakers in my ceiling and they sound pretty good. The space behind them is not huge, but the insulation is fiberglass, not styrofoam so it allows for the air behind the speaker to move to some extent. Would still like to add a 200W powered sub, but She Who Must Be Obeyed says no.
