Pops - nice to see you. I picked up a pair of 3.6s last year and listened, and said wow. Then I measured it and said wow. Then I looked at the crossover and said wow. The 3.6 in 1992 followed the 1990 2.2. For the 3.6, Jim had delved into finite element analysis to make serious refinements to the driver motors to radically lower distortion - and Vifa loved the collaboration. Lots of that stuff is now in broad use.
The 3.6 was the last Thiel product in which I directly participated in the development. After that my work was almost entirely process and capability development for the coming larger products.
That tweeter was developed for the CS5 and trickled down to the 2.2 and 3.6.