Hello Scott,
Good to meet you. In these 262 pages there has been barely a whiff of mention of the CS2. I'll attach a tribute I wrote to the CS2 several years ago and add some here.
Generally first generation Thiel models survive a few years before they get replaced by what we learned first out. The CS2.2 (1991) came seven years (longest run) after the 2 (1984) with over 7500 pair sold - most in our history. Its clear mission was as trickle-down from the model 3 plus benign tradeoffs: Less bass extension, less output capacity, smaller woofer allowing an octave higher transition to smaller midrange for easier transition to the tweeter. It worked.
I'll add that the cabinet material :1-1/8" industrial particleboard of 100% spruce for almost double the stiffness of the later 1" MDF made for one of the best cabinets in our long history.
To your question, the XO transition serial number was 4901 about 2 years in. Rob Gillum of Coherent Source Service can tell us the particulars, but I have the later schematic. I can supply some back-story. Larry Archibald, then publisher of Stereophile loved the CS2s, but niggled them more than once in print. I found out more than a year later that he listened exclusively without grilles, even though he was told and other reviewers enumerated how integral the grille was to their performance. We wanted Larry to update the record with his better assessment, which he wouldn't do (egg on his face). So Jim looked for an improvement and found an extremely subtle change which gave Larry a scapegoat. Short story is that the grille's absence accounted for the lion's share of Larry's complaint. Also, you may not have the 1" butyl tape anchoring the grille board to the baffle, which brings further significant improvement.
I agree that the CS2 is worthy of upgrade and may have been hot-rodded by some on this forum. But things get a little sticky. That tweeter and midrange are no longer available. The woofer is early but true Jim Thiel with many enhancements. It will stay. Rob has a midrange drop-in if a re-engineered unit proves unfeasible. Understand that newly developed drivers are to fit multiple products in order to justify their development cost. The CS5 needs a lower tweeter which is now an unviable 2" MB Quart dome, and the CS2 and 2.2 need a small midrange. A 3" Thiel driver might fill both the CS2 and CS5 needs. It would use the double-cone geometry and Jim's lifetime motor improvements. This is not a front-burner project, but of great personal interest to me.
Bottom line is that mid and tweeter changes require crossover changes. So you don't want to dive too deeply tweaking around obsolete drivers. All that said, there is some low-hanging fruit for you. Replacing the series resistors with Mills MRA12s makes for an inexpensive and lovely improvement. There are 1 tweeter and 2 midrange feed caps to replace with Clarity CSAs to significantly clean up the sound. Of further note, as many on this forum know, I've been developing new internal wire. It is lab proven and now being developed for manufacturing. It incorporates new art and I am as thrilled as can be about its upgrade performance, including affordability.
Within the foreseeable future your speakers will be formally addressed. For now, I probably have those caps for you to experiment with, and the resistors are readil available. Send me a PM if interested in wading in.
