I was initially undecided whether to post this under the "speakers" or the "advanced snake oil" topic.
Eminent Technology TRW-17 Rotary Subwoofer
http://www.rotarywoofer.com/
And, "How it works" http://www.rotarywoofer.com/howitworks.htm
A subwoofer without a cone. Essentially, it consists of large fan, which is equipped with a variable-pitch propellor, the pitch being controlled in amplitude, and direction, by a voice coil mechanism.
An interesting, if not entirely practical, method of generating very low frequency, powerful sound waves.
/ed b