Free air resonance

I forgot to mention this but honestly DIYaudio is a much better place for speaker building questions than Audiogon.  Lots of builders with first hand experience into all sorts of designs. 

Best of luck,

Erik

@unreceivedogma , That is exactly the point. You want as little baffle showing as possible. I just finished building new subwoofers, They are 30 inch long, 15" in diameter with a 12" driver stuck in both ends. The construct is easy. I did it for different reasons as subwoofers do not image. 

@unreceivedogma 

Sorry, I must  have misread.  I thought you said you had the Velodyne crossed at 2k!

All the best.

@mijostyn +2 @mahgister +1 @erik_squires This has been a fascinating read and I am impressed with all the sharing of knowledge. I just joined because (to me) I have an odd question and don't know how to start a new thread, and also because it ties into this thread. I have an 18" driver (normally I don't go beyond 15", but this has a BL 31, so I figured I had adequate cone control), and maintains a SPL of 96+dB between 100Hz and its Fs 38, which is my relevant range for this sub. The curious thing is that its free-air response is flat enough that it stays above 93dB beyond its Fs and down to 25Hz, and I would like to build a cabinet that takes advantage of this, a cabinet that can extend its response from 38 to 25. Its Vas calls for a 4.13 cu.ft. cabinet, and its compliance is fairly stiff with a Cms of 0.05mm/N. With its Qts right at 0.40 I'm torn between a ported and a sealed. It moves a lot of air with a Vd at 1286 cc, and of course, that's without much excursion. So, my question is two fold: how can I build a cabinet to drive the response down to 25Hz? And if so, does the cone stiffness hinder or help, and how can I take advantage of the driver's properties? Any help would be appreciated! 

@hsbrock  Really you need a cabinet simulator and to spend more time at DIYaudio. :)