Thiel Owners

All this talk of amplifier power got me curious so I checked the measurements of some of the stereophile reviews.  The 3.7s have a minimum of 2.4 ohms which is pretty low but they are also pretty sensitive so overall the are a difficult load but not exceptionally so.  The 2 2s are actually not that difficult of a load with a minimum 3.5 ohms impedance.  This is in line with my experience as I have found that they do fine with a Yamaha Home theater receiver.  I'm sure more would be better but they're pretty darn good this way.  I can see why the 7.2 would be an amp killer since it's a tough load impedance wise and also has low sensitivity at 85db.  


https://www.stereophile.com/content/thiel-cs37-loudspeaker-measurements
https://www.stereophile.com/content/thiel-cs2-2-loudspeaker-measurements
https://www.stereophile.com/content/thiel-cs24-loudspeaker-measurementshttps://www.stereophile.com/content/thiel-cs72-loudspeaker-measurements

@tomthiel, Would you please offerer your considered opinion on my 09-17-2018 musings?

As I’ve alluded to previously the sensitivity ratings can be confusing. In practice they’re really not as sensitive as they might appear at first glance.

unsound - Indeed the matter is not simple; it requires some study to understand. One good article from Benchmark is available on the web.
https://benchmarkmedia.com/blogs/application_notes/speaker-efficiency-and-amplifier-power There are other good articles and texts to study.

The relationship between voltage and power sensitivities produces a large array of interrelated results in the speaker and power amp. The common way to specify the sensitivity of a speaker is to state both aspects: voltage and current ie, 88dB @2.83volts @ 4 ohms. As was said previously, that voltage sensitivity would be (-3dB) or 85dB IF it were at 8 ohms, but it is not. And those two speakers ( 4 and 8 ohms) will act differently from each other in many regards and require amplifiers with different characteristics than each other.

Jim Thiel didn't make low-impedance speakers to torture amplifiers or listeners; there are practical limitations of physics. He chose underhung motors which require a 2-layer coil to remain short enough to get the significant low-distortion advantages of the topology. That coil requires a wider magnetic gap. Even with huge magnets, the maximum efficiency of that driver is lower (half) than a normal overhung motor. Given the point of diminishing returns of that topology, the maximum impedance of that driver is established. More wire turns (higher impedance) yields lower linear excursion and higher mass for lower efficiency. And so forth. So the driver parameters settle where they settle. Then, Jim chose to balance, compensate and correct many anomalies of driver response over a very wide operating range necessitated by the 1st order slopes. Each correction element lowers impedance further. And in the end, the impedance is maddeningly low. Jim's rationale was that amplifiers can be found to drive low impedance loads whereas the speaker constraints (described above) are immutable. Focused gaps and rare-earth magnet geometries were all applied to raise base efficiency as much as possible. Thiel drivers are far more sophisticated than the vast majority of drivers in the marketplace, and their distortion performance is an order of magnitude better. I guess the low impedance is a price we pay.

I direct you to the Benchmark or other articles to explicate the relationship between voltage and power. Once the relationship is understood, the rating scheme becomes more clear.

tomthiel
Thank You for the detailed explanation and more insight into Jim's design, philosophy.  Hope you are well and getting ready for Fall.

Happy Listening!