Thiel Owners

With respect to "ease of drive", I looked at the CS1.5 which I believe do not use "Thiel designed" drivers but more or less "off the shelf".  Based on Stereophile measurements, the impedance minimum is about ~3.7 Ohm at around  200Hz.  Based on that, I assume the drivers used in the CS1.5 are 4 Ohm design.  The overall impedance of the CS1.5 is not that different from most 4Ohm speakers using conventional design approach.

For comparison, I ran a quick simulation on my time-phase coherent design, all using 4Ohm drivers:
1. For a 2-way design, minimum impedance is 3.6 Ohm at also 200Hz.
2. For a 3-way design, minimum impedance is 3.3 Ohm at around 160Hz.

But using a more conventional NON time phase coherent methods, the impedance is about the same, therefore my guess is time-phase coherent is not the real reason for being "difficult to drive".

@jafant 

That’s a question for Ayre. My guess is the firmware makes zero difference to the sonics, probably more to do with the display and remote operation. Gary at Ayre will be able to answer your query.

Andy - a couple of points in a very complicated maze. Choice of impedance indirectly includes slopes because slow slopes require less moving mass to avoid self-attenuation on the treble roll-out, and lower inductance for the same reason, and therefore fewer coil winds.

Note that the 1.5 drivers were entirely developed by Thiel in-house; they include under-hung coils, copper shunts, focusing pole and plate geometries, etc. Thiel had a complete driver development lab that was fairly robust by the late 1980s. We developed our drivers and turned the designs over to Vifa for production engineering and supply. We were too small to "own" those designs, so we allowed Vifa to put them in their catalog to recoup their tooling expenses. So, they could be considered "off the shelf", but they got on the shelf by our putting them there.

I have an eccentric theory about why phase-coherent x time coincident speakers are "harder" to drive. I believe that coherence allows our auditory perception to be accepted as "real" and not "reporduced". We take that "real" input much more seriously, and many aspects become sonically important, whereas they were not even heard in the incoherent speaker. I have previously described how I came to form this theory - it is an important leg of my sonic understanding stool. That phase-related amp misbehavior from the amp driving the Thiel low impedance load is obvious, but if driving a high-order low impedance load, I believe it might not be obvious.

Note that the 1.5 drivers were entirely developed by Thiel in-house

OK, I see.  I just thought they did look similar to some of the Vifa drivers.

I have an eccentric theory about why phase-coherent x time coincident speakers are "harder" to drive

I also notice that if I disconnect the tweeter, the sound becomes subjective less "dynamic".  I also notice that higher order filter speakers do have more perceived "slam" vs. first order filter speakers as if the drums become more "dynamic".  It may have to do with how high frequency affects our listening.  

But then beyond this, I am just guessing ...