Thiel Owners

Prof - I’ve only heard the 3.7 and 2.7 once, when auditioning the final prototype 2.7 at the Thiel factory in 2012. We all heard what you are hearing.

There’s probably more to it than the baffle. A few years and $six figures were spent optimizing the 2.7 within its budget parameters. The aluminum baffle is a contributing element, but any upgrade would have to be from outside, since the interior has multiple shelf braces in the way. A person might route a pocket into the MDF baffle front to seat a custom aluminum plate. Serious undertaking that I doubt Rob would take on - but ask him. You would get significant improvement using counter-top laminate (Formica, etc.) rather than aluminum.
An effective and feasible upgrade addresses the 2.7 midrange xo feed which goes through a 400uF electrolytic cap as well as a series 20 gauge feed coil, without any shunt to ground. Jim never used electrolytics in series feed stations (after the 02 in 1976). That "caught in the box" effect is something that big E caps do. I have developed some substitutes from Clarity Cap 100uF x 160 volt CSAs. I doubt you have room in the enclosure for them plus they’re fairly expensive. Note that Jim’s solution for the 3.7 is a cap bridge with multiple 75uF PPs. The feed coil in that station in the 3.7 is 18 gauge for about double the current / resistance performance.
If I were in your shoes I’d consider the following:
Baffle treatment: remove the drivers and the threaded inserts (if any).Mount 1/2" (or larger) birch dowels into holes drilled into the edge of the driver openings, at least an inch and preferably farther behind the front surface. Wood screws into that side grain of the dowels will couple the drivers more tightly to a greater cross section of the baffle. Use viscous gasket goop behind the drivers (Permatex type 2 non hardening) to damp the natural interface resonance. That mounting on a formica face gets you pretty far up the performance ladder.
Crossover: replace that 400uF E-cap with 4 @ 100uF in parallel. Consider replacing the bypass caps with ClarityCap CSAs. While you’re in there I’d swap in some Mills MRA-12 resistors in that series midrange feed. Same for the series feed in the tweeter.
That’s some low hanging fruit and something that a good bench tech could handle if it’s more than you want to tackle. Rob may have suitable parts or advice, or you may contact me for specs and sources.
The 2.7 is a very nice speaker and in some ways easier to take on a broader range of material and amplification than the 3.7. But immediacy and detail are relatively compromised.

Just in case anyone is interested, Saturday Audio Exchange in Chicago is listing a pair of CS 7.2 in teak for $4499.  They are also listing an MCS-1 for $899.

Tom,
Thanks very much for the detail.   I'm not a handy-man type so wouldn't do that myself, but I'm saving that info and maybe some day I can get a local speaker repair shop to do it for me (if not send them to Rob).


BTW, speaking of getting the 2.7s to "disappear":


I just tried a fascinating tweak with the 2.7s.


To backtrack, I spent a month several years ago putting together an isolation platform for my turntable.  I bought tons and tons of footers and various isolation material (hard and soft), testing most of them with vibrometer apps etc.   By far the most effective were the Townshend "seismic isolation pods."   They are a spring-based design that holds up the heavy turntable and layered platform.   Without the springs if you stomp around the equipment rack with a hand on the top shelf, you can feel tons of vibration.  Also a Seismometer app measures plenty of big vibration spikes with ringing.  



But with the spring pods under the platform, stomping around you can't feel anything getting to the platform, and almost nothing registers on the vibration app!   So quite objective verification that at least some register of vibration is not getting through.


That experience made me curious about the spring-based speaker isolation platforms sold by Townshend, which get great reviews (what doesn't?).    But those are pricey so I thought I'd try an experiment with some cheap spring-based footers on amazon. 



I placed them under the Thiels and just finished listening for over an hour.Wow, they work!  The effect was very similar to when you get a subwoofer dialed in really well - not extended bass but a perception of clearing up and tightening of the entire frequency range, starting in the low bass.  Bass instruments were tighter, floating better in their own space, every thing had a bit more clarity top to bottom, and the speakers disappeared better, the soundstage taking on more of that wide CinemaScope width of the 3.7s, instruments to the side less stuck in the speaker!


I certainly wouldn't say they suddenly sounded just like the 3.7s, but it sure was fascinating for a cheap tweak!
The problem is the speakers get a bit tippy on the spring footers so I don't think I'll stick with that particular solution (because I have a lot of foot traffic in that room right past the speakers to get in and out).   I'm sure with a bit of ingenuity one could make some outriggers using the footers for greater stability.   But I have a feeling I may pick up the Townshend speaker bars in the future.

If I were going to try to reinforce an mdf box the first thing I'd look at is porcelain floor tiles.  They're incredibly stiff and tough.  They don't resonate much but what little they do is at a high frequency.  I'd think combining them with mdf would be an ideal combination.

jon - you're on it. When developing the CS5 cabinet I explored custom ceramic tiles for the interior, attached with a researched mastic adhesive - it worked extremely well. There were two big problems. 1: it was too heavy to ship and handle. Dealer home delivery was the deal breaker. 2: the tiles were not always flat and the ratio and durometer of the adhesive layer would change the tuning of the enclosure depending on adhesive thickness variability, thereby changing the final tweak voicing of the system.

For your in-place situation, #1 may not matter. #2 is a small issue (and no, I don't remember adhesives options or winner 30+ years on.) It's worth exploring. Also, you will change the acoustic volume of the enclosure, but it won't matter a lot. I suggest finding the most active surfaces with your fingers or stethoscope and treating those. High likelihood includes the top and halfway up the sides. Please let us know what you do and how it works.