Once again, I was treated to a demonstration of Eminent Technology's $12,900 TRW-17 rotary woofer and once again I was baffled by its seeming lack of practicality, while being amazed at its creative approach to producing the lowest notes.
For $12,900, you get the motor (pictured) and bass manager and amplifier. However, you also need to build a room adjacent to your listening room (or, more likely, home theater) in which to house it. A vent or crawl space ports the bass into the room. And then, you'd better really brace your room, the bass chamber, and, most likely, your foundation in order to handle all the stress 5–7Hz puts on your structure.
At The Home Entertainment Show this year, as last, ET built a braced and substantial chamber, but the effect was more of the structure rattling than a sense of deep, deep bass. It was fun, but also annoying.
If you've got the room, the budget, and the inclination, the TRW-17 does add a whole new dimension to the term "bottom octave."