Thiel Owners

A Renaissance 3.5 would require all new drivers. The extant woofers are bulletproof and decent, but lack the sophistication of later designs. They are a 1985 solution. The replacement midrange needs to be a full range driver, which is findable, we just haven't yet succeeded - same with the tweeter. The XO upgrades I have been developing this past year all apply to the 3.5 to up the performance league dramatically.
The EQ could also be executed better. It is all discrete, and therefore upgradable, but it is likely that a talented circuit designer could do the job better today. Now, IF the EQ could be a requirement rather than an option, then other possibilities emerge. The midrange / tweeter could run on one channel with no boost to its low end. The equalized woofer would run on the other channel for good power balance. The crossovers could be incorporated into the EQ before the power amplification stage. It is possible that the woofer, or all the drivers could run crossoverless for direct, lossless feed, or with driver-specific and tweakable elements installed in an outboard XO near the cabinet. Such an active-crossover analog solution would squarely fit Jim's approach and sensibilities, and indeed one of the original design pilots which was deemed unfeasible in the company's fledgling state.

As an aside from history, I really like the 3.5 cabinet which shares technologies with the CS2 and 3 but obsoleted by the 2.2 and onward. Those early cabinets used MDF only for the baffle for its sculptability. The walls are 1-1/8" industrial particle board laminated both sides - for about 1.5x the stiffness of later 1" MDF cabinets. For production management reasons we landed on 1" MDF as our sole cabinet material. But the particle board is better.

Obviously, I am personally more excited by this potential upgrade than by pairing the non-eq 3.5 with a sub. But it would take lots of doing by someone(s) with youthful talent and vigor to pull it off. BTW: the CS3 cabinet is functionally identical to the 3.5; the combined 3 and 3.5 models sold about 7000 pair, and the 03, 03a adds another 2000 pair build of 20mm FinPly (better than BalticBirch or ParticleBoard). Hmmm.

Excellent discussion and an exchange of ideas moving the 3.5 into 2020 and beyond.  The addition of subwoofer(s) seems a logical progression given that critical parts for the older EQ might not be readily available.I can remember  1985, a long time ago, indeed.
Happy Listening!

tomthiel
Keep up the outstanding Renaissance Thiel work.
Happy Listening!

@tomthiel, as usual an excellent response.

I do think that 40 Hz is not too much to ask of a 10" woofer.
Of course, as has been discussed before these suggestions could double one’s amplifier budget. And, with 1st order crossovers there would be quite a bit of overlap, suggesting that even more so than with other configurations, using identical amps would be preferable. It might be more palatable if there was an upgrade path from 2 channels to 4. Or more?
It’s quite a testament to all at Thiel Audio that a 30+year old speaker is still so relevant today!

Other than the huge amplifier requirements and depending on perhaps too complicated a crossover when a more thought out baffle arrangement might have sufficed, I don’t consider the CS5’s to be unsuccessful. When properly powered, in the right room, they are still amongst the best I’ve heard. Perhaps you mean from a marketing perspective?

Could your suggestions applied to an updated 3.7 with a sealed box and woofer drivers from the smart subs might be a consideration? As I understand it, as is common with so many integral self powered subs with Class D amps, the amps are often problematic. Would the sub drivers have huge power requirements? Too much to be practical with Class AB amps?

@jafant , I don’t believe eq parts would be a concern.

Unsound - agreed on 40Hz, and even 20Hz at moderate levels in a moderate room with moderate music. I like the 20Hz 'sound' better than 40Hz, possibly because of the relative lack of low end phase shift, to which I am sensitive. The bass response effectively starts as low as there is program material. There are ways to successfully aid the bass against overload ie subwoofers, etc. I use an SS2 behind each main speaker, whatever model. In the Thiel passive XO mode they contribute only below around 40Hz (plus overlap), and there isn't much music down there. But nonetheless, that supplementary deep output provides local air pressure to aid the main woofer's room coupling. I'm surprised how much more authority the bass gains. 

Please say more about 2>4 upgrade path.

My CS5 comment was market-based. And as you allude, most of that was self-inflicted, in my opinion. The product is good, especially the 'improved' version with Jim's driver designs. It's not common knowledge, but I consider the CS5 and the squandering of its potential segue into higher range markets to be classic self sabotage. The product as designed wanted a $15K (some said higher) price and another 3 months in development. Rather than settle into that league, Jim and Kathy were adamant about keeping it under $10K. It didn't 'fit' the market there. There was much too much speaker there to make sense, and its amp requirements etc. took it into the higher league anyhow. (Note that we had 100+ carte blanch firm pre-orders with no price stipulation.) You might detect my flabbergast these 30+ years later; this rant has never taken words before. One example of 'what happened' is that I had designed the baffle to include 3 stones (marble, granite & basalt) in 3 particle size ranges for an inert - extremely well-damped, good-looking baffle. The stone mix had enough variation and visual texture that the gel coat would be clear, to see into the stone matrix - all quite subtle since ground marble takes dye well. The casting molds required higher maintenance, and it would be 50% heavier, but what a baffle! I found the right supply partner in Atlanta and settled on $100 / each with quantity guarantees, etc. (Note that a company like WA might add $25K for such an element). I was elated. That is until I learned that Kathy came behind me, capped the price at $50, reduced the spec to ordinary bathtub cultured marble, and gloated over the cost reduction, all on their way to a $9300 / pair introductory price, which caused market confusion against the $15-$20K pre-marketing by distributors and dealers. End of rant.
It's called family business. The J&K alliance was internally infamous. They abandoned the CS5 platform and stated that it was 'too expensive' to sell through. I suppose polite professionals are supposed to keep such things under their hats. But I think that you fans might benefit from some leaks whose potential harm has long-ago elapsed.