Note that I am aware that some might want to go farther afield with cost no object components and others may balk at the significant cost of my choices. My vision is to find affordable solutions that reach the next performance / cost plateau.
I will add that I think Tom Thiel’s choices are *very* sensible. The upgrades will almost certainly (can’t say for certain ‘til we listen!) yield a significant SQ improvement but without going beyond the budget of most serious listeners.
Left to my own devices, my choices would have been similar to Tom’s in some ways. I was honing in on a solution that would have added a substantial (30%) Clarity CMR bypass to CSA coax feeds. This would have been more expensive and not necessarily overall better than what Tom outlined. In his research, Tom has learned that certain bypass practices can have detrimental effects! Elsewhere, I was going to add small polypropylene bypasses to the extant caps. Tom’s solution is far better, replacing the electrolytics in the shunts with the custom 160V PPs. We are fortunate that Tom is able to work with Clarity to have this cap made to spec. An off-the-shelf solution would be very expensive and with ginormous caps that would be very difficult to fit.
These upgrades will not be inexpensive ($TBD). All XO parts are replaced - most caps are custom - except for Thiel’s custom 1 uF bypasses and the coils. As I wrote earlier, if I were to replace my CS2.4SE with something new I would start at something like a Vandy Quatro or Vivid B1; $15K speakers! After these upgrades, I suspect such a search would have to reach to something like the Vandy 5 Carbon, a $30K speaker. In other words, the CS2.4 is a seriously good speaker in stock form and optimizing its crossover should elevate its performance to the next tier (or beyond). Do I want to live with a speaker whose neutrality, transparency, and resolution exceed or rival anything up to $30K? And for the “only” cost of the upgrade? Hmmm, decisions, decisions ;^)
As Tom wrote, some owners may want to go even further. Earlier I linked to Jim Smith’s outboard XO for his Avantgardes featuring a rack of Dueland caps and resistors. Would that approach outperform what Tom Thiel has outlined? I hope so – that’s at least $20K in parts! But we’d have to listen to know for sure. To my thinking (and budget) that is not sensible for a CS2.4. Maybe you CS3.7 and 7.2 owners will choose to push the limits? But remember that Tom Thiel’s “base” upgrade is a notable upgrade even for those models.
later production 3.7s have Chinese made crossovers which seem to have some polyester caps where polypropylenes are specified. And those are built on printed circuit boards
My SEs also are on PCBs and with some MKT caps where Jim Thiel’s schematic specified PP. My pair was built in 2012 (the year Kathy Gornik sold Thiel Audio) and are among the last SEs built. @jafant I suspect your pair are similarly equipped. For us, Tom Thiel’s upgrade will probably be an even bigger jump in SQ than for owners of earlier SEs.