Thiel Owners

I think the reason for active is to couple drivers directly to the amplifier and get rid of crossover components. Also a passive radiator shares same compartment with the woofer and is coupled together by the air pressure, so I don't think two active woofers of different designs would work. The SS3 amp is designed specifically for bass reproduction with specific Thiele/Small parameters in mind and proprietary to the drivers.
Though nut to crack, but good luck! 

Until i got my 1st taste of the CS 2.4, later on the CS 2.4SE (my reference)
I did not think much of a passive Bass radiator? After hearing these outstanding speakers, I was "hooked" and  a believer!

Happy Listening!

Hope you guys are having a fun and music filled Thiel week!

@robinbarbour Understood.  What I was getting at was the form factor of the CS6. Obviously it would need a sealed chamber at the bottom to isolate the 12" sub from the 10". 

I was also thinking about the crossover considerations that Thiel already took into account when developing the specific PX02 that could marry an SS3 to a CS6 (if it even exists). Maybe start from there, and figure out if freqs are augmented rather than crossed over, and the impact that has on the main driver and its radiator.