oxfordamps,
Regarding crossover upgrades this is one of many steps to catapult the 7.2 into sonic nirvana.
The notch filter upgrade for upper mids uses electrolytic caps as they are high value (4-100uf) and using a film cap instead would have been cost prohibitive when Thiel debuted the 7.2.
Fast forward and as endusers we are not in that dilemma. This upgrade is not relying on caps of higher quality for improvement. It is a better design and how to implement the caps with the formulation Tom devised.
The object on this notch filter is it will become an immediate upgrade to other models as many have a notch filter, albeit not as large as the 7.2.
This test is a few different formulations as the cap values are not off the shelf caps. Tom works with winding companies to wind values and his unique design into a cap. Essentially its a cap within a cap within a cap etc...
Once this test is concluded then the rest of the upper mid crossover will get implemented. Adding custom CU foil caps in Thiel's should excite every owner.
Then lower mids, HF, and LF will be upgraded to complete the four way. Toms Biflow technology will be utilized throughout the crossover. His internal wiring will bring an immediate sonic improvement as I've heard it.
There are many other upgrades too be added and I'll leave that to Tom to disclose.
Hope this helps.