Originally Posted by smcmillan2
Sorry, should have said "higher SPL in the 15 - 50Hz range" (the difference in the ported vs. sealed graphs scottvalentin posted). That knee on the ported graph shows quite a bit more in that range, but of course the box is twice the size too.
Might be duals, Scott would have to answer that. Doubling the cones should give you ~3dB increase, but the curve remains the same.
Sorry I was away from the computer since the AM.
I just modeled ONE driver. Keep in mind the SPL levels shown are at 1 meter (I think), so the level at the listening point will be lower.
The FS you were reading above is the FS of the sealed box system, same as the QTC being .67 as a system with that driver in that size box.
The advice on bracing is good - every 8-10" have some form of cross or window bracing, front to back, side to side, and some top to bottom, etc. Even just some 2X4's work well.
With 4 of these units in sealed boxes, you will have a LOT of headroom assuming they are sufficiently powered, so you could EQ them very flat in room to very low frequencies. So you may be perfectly happy with them sealed. As
says, if you aren't happy, you could then build ported boxes to get the output you need.