[chessman]

They are just a transducer (shaker) bolted to the furniture frame that attempts to correlate to frequency response in the unheard but felt range. They should be adjusted to give a subtle fill, but even then they activate during quiet music passages in a manner that I found unpleasant. The design is primitive so I would think a knockoff would work as well as an original.

These things are a mechanical “fix” for the inability of the sound gear to energize the room in the under 40H range. For a dinosaur movie, yes. For house music recorded digitally, no. YMMV.