Regarding driver wiring: there is a simple trick if you have a multimeter. Get access to the driver terminals, feed a signal to the speaker. Measure the AC voltages at the terminals. The woofer should be the highest, midrange much less and tweeter less than that. If a tweeter shows higher voltage than the mid, it is mis-wired from the crossover. Get Rob’s help to straighten it out.
Regarding cabinet construction. Thiel speaker walls have always been multi-laminates. Solid woods are less than desirable due to variable, under-damped and unpredictable resonance modes. The outer layer is a face veneer, matched by an interior backing veneer, each about 0.020" thick (5 pieces of paper). The 3.7 and 2.7 share their substrate panel which is an engineered sandwich of birch and other veneers glued into the curved shape under heat and pressure. In a historical context, that sandwich was envisioned from the beginning; it just took time to develop into a real product.
In the 03 development in 1978, we landed on Baltic Birch plywood as the substrate. (In fact we used FinPly, a higher quality alternative.) That BB/FP is twice as stiff as Particle Board and 3x as stiff as MDF. But it is under-damped and unpredictable in its resonance modes. Over the years, I messed with making our own build-ups, including bending the panels, which solves most of the inherent panel movement. But, for a small company making moderately priced products, those technologies were beyond our reach. The CS2, 3 and 3.5 used 1-1/8" industrial particle board plus face and back veneers for an extremely rigid and well damped panel. When we developed CNC capacity in the late 80s, we converted to MDF because we could pack engineered shelf braces into the construction. Check out the cutaway in the Stereophile review of the CS2.2, which was our first product designed for CNC manufacture. Nonetheless those well-braced MDF cabinets exhibit some resonances, and quieter is better. For the 3.7, Thiel found a subcontractor in Atlanta to make the unfaced custom curved panels. Thiel added the face/back veneers in-house with a custom curved mold press. That same panel is trimmed for the 2.7. The precision machining, including landings for the internal braces, were done on Thiel’s custom CNC.
Regarding drivers - Thiel designed its own drivers beginning in the early 80s for the CS3 introduced in 1983, as co-developments with Vifa of Denmark. Our deal was that Jim would design what Vifa could manufacture and offer to the larger market to amortize their development and tooling costs. That was unique in the industry and many Thiel design innovations worked their way into generic Scandinavian offerings. When our requirements eclipsed those of the broader market, we had to create our own driver-making capability, not because we wanted to, but because that was the only way we could get what Jim wanted. The CS5 (1989) drivers were (modified) off the shelf, except for our exclusive UltraTweeter. The following CS2.2 and CS3.6 were completely Thiel-designed x Vifa-made for us exclusively. All further products’ drivers were built in-house. By the time the 3.7 was designed in the mid 00s, Jim’s illness had progressed, and ways were developed for outsourcing most critical parts. Thiel, along with Vifa, ScanSpeak and others, co-developed FST as a high-quality Chinese driver source. Things change, and FST became the only feasible way to make those custom flat diaphragms. Many of the high-end Scandinavian drivers are coming from FST and other Chinese suppliers. Most of Thiel’s products since the mid 90s have early drivers built in-house and later drivers sourced from FST. In most cases they are equivalent, but in some cases, like the PowerDriver in the PowerPoint, etc. the tweeter module can no longer be replaced separately. Thiel could pull off that stunt in-house, but FST insisted it couldn’t be done. And you can’t make a supplier do what can’t be done.
