Thiel Owners

@yyzsantabarbara , I think the first graph on each of the respective links might explain what's going on:

KEF LS50 Anniversary Model loudspeaker Measurements | Stereophile.com

Thiel CS3.7 loudspeaker Measurements | Stereophile.com

Jim Thiel seemed to be rather cognizant of the effects of a steady vs. a variable impedance load on amplifiers. As much as a low impedance is tough on amps, amps don't typically care for a varying load, especially tube amps. A variable load can exacerbate the mechanical / damping issues of analog meters as well.

@Imhififan, at these impedance loads the rated sensitivities can be misleading.

@tomthiel, et al, Saw this on another site:

Renovating Thiel CS3.5 Speakers | Page 2 | Audio Science Review (ASR) Forum

Post #27

Is there newfound hope?

Thanks for the info.

unsound - thanks for that link; those guys are serious.

But their approach is different than mine. My interest is in updating and augmenting the original design for better performance and future maintainability while honoring the extant supply relationships we built over the decades. The EQ has several obsolete parts for which I have found modern replacements and am developing an update and an upgrade. More news when there's real news.

The tweeter and midrange were off-the-shelf and are obsolete with no satisfying replacements. My approach is to re-purpose the tweeter from the CS5/3.6/2.2 and midrange from the 3.6 which were 100% Thiel-developed and are the terminal drivers of that discrete driver architecture.

The woofer will (at least for now) remain unchanged. The CS3 woofer was our first ground-up design and substantive collaboration with Vifa. It has Jim Thiel breakthroughs of copper shunts and shaped motor components. Its voice coil is over-hung, since we hadn't yet invented underhung motors; but it has very long excursion, rubber surround and generally built like a tank; and it remains serviceable. Furthermore, its performance in that cabinet is custom engineered and highly successful. The CS3 woofer is upgradable to CS3.5 performance via a polymer cone coating available from Rob.

So, my direction is to implant the Thiel UltraTweeter and CS3.6 midrange, both with possible enhancements along with necessary crossover changes and upgraded parts to achieve performance beyond the 3.6, hopefully significantly.

Of significant interest to me is the sealed bass quality, high system efficiency due to the EQ bass boost, and overall high performance in a very compact package.

Progress is being made.

@tomthiel, I was really trying to specifically point out Post #27 where the poster found a way to resuscitate a midrange driver that might have otherwise been discarded. There may be hope for those that might have otherwise given up in the meantime while your project comes to fruition. 

The last paragraph of your last post succinctly describes what made those early CS 3 series so great (and the above 4 Ohm load!). That you are trying to make them even better is truly exciting!