Has anyone ever heard of this?

http://www.eminent-tech.com/RWbrochure.htm

it's an ultralow frequency subwoofer -- for the 1 (yes, 1) to 30 Hz range, +/- 4 dB.

more info here:

http://www.eminent-tech.com/howitworks.htm

I have to wonder how this might work with an LFM-1 Plus and a crossover.