I think this is the most impractical thing I have probably ever seen, and it has been posted over and over again to every audio forum I have visited in the last week. This is getting annoying, like that Royal Device "world's largest folded horn" in the floor of some guy's specially-built listening room that everybody seems to feel the need to alert us to. This is insane and needs to stop.
Yes, we have all heard and read about the Eminent Tech 'fan subwoofer'. Some justification for why it is impractical: Hugely inefficient (the motor runs and draws power even when the blades are not pitched), no baffle (adding to the huge inefficiency by an inability to create a large pressure differential in a big room), and mechanical noise (motor bearings, linkages, propeller rotation).