[Josuah]

You really haven't felt frequencies that you can't hear? I find that a little surprising given you have essentially the same output as 2x15" drivers and your response curve indicates 100dB at 12Hz or so, when you're not pushing them to the maximum. Supposedly if you reach 140dB or so at these low frequencies, you can hear them instead of only feeling them. But I suspect your house might collapse as well.

Maybe you just don't have material that makes use of those frequencies?

Here are a few movies that had inaudible, but physical, low-frequency effects that I can recall off the top of my head. These are movies I've felt myself, and I don't know if they have data below 12Hz.

Lion, Witch, and the Wardrobe - when one of the giant hawks/griffins/whatever flaps over the battlefield. My pant leg flapped.

The Incredibles - when Mr. Incredible drops the little vehicle on two of the guards. Watching this scene with the 16-46PC+ subs made me jump, where as in the theater and with the Velodyne 12" I didn't notice.

Black Hawk Down - f*ing Irene scene, helicopter blades I can only barely feel minute movements near the subwoofers (I can't really feel these - they're supposed to be at 7Hz).

Appleseed - when the giant robot crawlers are moving around.

Steamboy - there's a lot of stuff throughout the movie.

I've heard War of the Worlds and The Hitchhiker's Guide to the Galaxy have some too, although I haven't watched these yet (I plan to).

Probably the best music source I have that exercises low frequencies is an album by Kodo. But since they're pounding huge drums, that's not surprising.