OK, the average subwoofer covers about three octaves - so does this device. On that level, I suppose there is some validity.

No specs on the prototype, but I’m guessing that the noise floor might be 40 to 60db lower than it’s maximum output and that the noise is in the audible spectrum while the expected output is not. The noise floor is constant even when arriving through a very large ported enclosure such as the attic or other adjoining space and a large pass-through and likely only about 20 or 30db lower than the listening levels of the average material level coming from the rest of your system. Acceptable during the majority of listening?

Oh, while this device might be installed somewhere for special effects, do most users have source material or playback and pre/pro equipment that will pass such signals? Maybe these guys will have some success in a very special market such as an amusement theater of some type.

In the “I like it” column, I like the principle of “leveraged” output. I’ve had an idea for a leveraged device for a little while now, but doesn’t involve a fan nor a target range of 5 - 20Hz.