The concept works with any fan. The noise of the fan is what we design for. The blades on the TRW-17 are flat and made of a plastic.
That's the idea. You obviously can get a perfect air tight seal, but because a fan can create static 0hz pressure without an airtight seal, it just has to be good enough to not allow the air to do a u-turn and short circuit.
If the fan has quiet blades and there is no pitch, the TRW-17 is very quiet. When you start throwing big chunks of air back and forth is when you start to notice the fan noise, but since this also produces bass proportional to that noise, the bass will win out unless you're sitting with your head next to the thing. And yes it is scary when it ejects all the blades, but that only happens with prototypes and hasn't ever happened with a production woofer.
Yea, we sell one driven by a 1/3HP motor and one with a 2HP motor. That is an awesome scene! https://www.reddit.com/r/onetruegod/