Sound Dynamics THS-3000 subwoofer. Never heard of them - til now.

I just picked up this sub on CL for $50. The specs are impressive. 150w MOSFET amp capable of 600w peaks. dB boost selector, phase control, adj. low pass filter, anti-clipping circuit. Bass response is deep and rich. Built like a tank. I think I got cheap due to lack of name recognition. Does anyone known anything about this brand?
Sound Dynamics made a three-way speaker, the 300ti, that Harry Pearson (TAS) praised and really liked back in the early 90's. It cost about $600/pair. SD was part of a larger Canadian speaker company (whose name escapes me at this moment). You have an excellent sub for a pittance!