Thiel Owners

Biannuzzi22 27june23

"I am seeing a lot of chatter about upgrading the CS2.7 speakers. Can anyone send me instructions on how to do this? In particular, it looks like using the Clarity Purity 1uf 800v capacitors is a good upgrade? Where are these located and how would I replace what is currently on the crossover?"

Crossover upgrades are, at this time, conversational rather than commercial. I hope to eventually have plans and kits, but not yet. The CS2.7 is the final Jim Thiel-esque product, developed after his death, but by the original in-house team with outsourced engineering help, and built in Lexington with traditional classic methods. It qualifies in my thinking as genuine and worthy of upgrade.

Clarity’s Purity800-S is their hands-down winner. Its internal circuitry is more sophisticated than the other PUR caps, plus the thick copper end caps and silver wire refinements. All that said, I find that replacing the stock Thiel styrene/tin - film/foil 1uF ’yellow’ cap with the PUR800 1uF is a lot of money spent on marginal improvement. I suggest you rather might consider unifying the split/bypass cap into a single PUR800-S where most appropriate (eliminating the bypass.) Your best prospect is the tweeter series feed which is now comprised of a 15uF PP and the 1uF yellow bypass. Replace them both with a single 16uF PUR800-S. (That leaves potential for a more sophisticated bypass, in the works, at a later time.)

The weakest link in the 2.7XO is the 400uF electrolytic cap in the midrange feed. I am working on an all-film solution which is not yet ready. My first focus is on early products to keep them up and running. New midranges and tweeters will bring later Thiel driver technologies and longevity all the way to the early designs. As various caps are finalized I’ll announce here. Stay tuned – a lot is presently coming together - I anticipate real progress this year.

Rob - good to see you making steady progress, and eagerly await your report on that parallel tweeter cap.

Regarding coils - bigger is not better (despite conventional opinion.) A significant consideration is the saturation frequency rf wire size. 18 gauge saturates at 17kHz above which turbulence results in distortion, heat and related instability. I consider 18 gauge the best compromise for woofers and OK for midrange with smaller being better and more so for the tweeter. That 20 gauge midrange feed coil is not an accident or compromise. Note the trimming resistors that follow it, so less coil resistance would not be an advantage. Au contraire. The dissipation factor of a coil is far greater than a resistor.

The 20 gauge tweeter feed coil was probably the best compromise between its required inductance and a resistance value that matches an available resistor value. I know that Jim would have preferred a 22 or higher gauge there if practical.

Also note that Thiel inductors were best-of-form from 1978’s model 03 onward. The 2.7 ERSE inductors directly trace their lineage all the way back to 1978 when Thiel introduced ’good wire’ to Acousta-Coil for the 03. At that time what is now CDA101 (highest grade) wire was an aerospace-only product developed for the Jupiter Deep Space Probe by ITT. The rest is history which I recounted in these pages years ago. I don’t think you’ll find better wire or winding, and thicker gauge would degrade performance - and make Jim squirm.

Thank you Tom , as always your knowledge and advice helps steer me in the right direction .

The series feed which is now comprised of a 15uF PP and the 1uF yellow bypass is on the mid range , also the 1uf is a Clarity cap the was " Made for Thiel " and happens to be the exact same size as the ESA 630v cap ( that was used on one of my boards .  Also as of now Clarity does not make a 16uf in the Purity series  and the ESA , MR and CMR are very large in diameter I believe that a 15uf 400v Purity with a 1uf 800v-s Purity cap would be the perfect solution which now you've got me thinking about replacing the ERSR 15uf 400v .

While the schematic says ERSE inductors , Rob and the tags that are still on them say they are from Jantzen .  When researching I discovered that ERSE does not make the values for the 2.7 .  How much difference would one expect by using a 0.68mH 20 awg  .569 DCR verse the 18 awg .440 DCR as used , or even using a 21 awg. .700 DCR or 22 awg .870 DCR ?  The 0.60mH is used on both the tweeter and the mid .

I did it again , I installed the crossovers with the new Purity 800v cap before taking a picture !  But I posted pictures of the board on the virtual systems before showing the original  (replacement by new Thiel)  1uf ESA cap .  They show the 4  x 100uf electrolytics replacing the 1 x 400uf .

vair68robert

Keep up the excellent DIY work!   Happy Listening!

Thank You jafant

While it has been a lot of work I'm sure that without the guiding advice from Tom I wouldn't have made this far or near this successful .  All I did was replace the old components with new and higher quality ones and made them fit into the limited space .  This is definitely not for everyone but if you can and are willing you will be rewarded with the results .