Regarding Thiel subwoofers - when I began my 2018 assessment of Thiel Audio’s value, I spent considerable effort to locate any/all information about the sebwoofers. I concluded that New Thiel had literally thrown it all in the dumpster. I engaged a reputable design firm and learned that replication of the circuitry would require significant reverse engineering costs. Jim kept his filters proprietary and performed all service himself. The early SW subs used Jim’s own amp along with his room-equalization circuitry. Those amps had a high failure rate. They were replaced by Canadian BASH plate amps. Jim’s room circuitry seems robust enough, but is without schematics or test points.
In my shoes, I put the subwoofer project on the way back burner. I have a pair of SS1s and an SS2. Their integration is phenomenal. They are fed from the power amp output. Their crossover knows the parameters of the bass rolloff of the main speaker. Jim implemented an actual dedicated crossover between each model speaker and the subwoofer. I’ve never heard it so good. Nonetheless to expand what has been said, the main speaker rolloff progresses to 24dB/octave to match a 24dB/octave subwoofer low pass rolloff, which adds another full phase rotation. That bass alignment is well executed, but lacks the kind of time coherence that we get from the main speaker above its low-cut range.
