Hi
I searched Google Patents but only found the Canadian patent for that.
The evolution of that was the commutated voice coil idea, then the Servodrive (the rotary version of the commutated coil), then the full rotary woofer and motor, the Phoenix Cyclone was an example made under license.
The attached picture was part of a "large" one of those full rotary drivers. 8 of these were placed at the exit of a 20 foot diameter cooling fan at the Redondo Beach nuclear power plant to cancel the low frequency fan noise.
Each of those had the displacement of 6x 18 inch woofers moving an inch peak to peak. The noise canceling system was in place for about 2 weeks before the earthquake knocked the power plant off line for good
https://patents.google.com/patent/US4531025A/en?q=(tom+danley+subwoofer)&oq=tom+danley+++subwoofer&page=1
https://patents.google.com/patent/CA1199875A/en?q=(tom+danley+subwoofer)&oq=tom+danley+++subwoofer&page=1
https://patents.google.com/patent/US4763358A/en?q=(tom+danley+subwoofer)&oq=tom+danley+++subwoofer&page=1
https://www.diymobileaudio.com/threads/phoenix-gold-cyclone-12-in-rotary-subwoofer-rare-working.453370/
