While I commend Stereophile for actually measuring some of the gear they review.The discussion is not really about Stereophile measurements but more about the underlying meaning of "time coherent" or "phase coincidence" (Tom terminology). My argument is a perfect "phase coincidence" is not physically realizable in real world environment irrespective of measurements. I think you can have a speaker that is "phase coincident" but only within a certain frequency range, NOT from 0 - 20KHz.
Even with a speaker that only has one driver, it will have different phase at different frequency, and yes it will have a proper step response, but based on Tom strict definition then it is not "phase coincident" at least not at all frequencies.
I am not criticizing Thiel products in anyway, it just seems that Tom was using an argument that is a bit unreasonable.
Tom,
If you look at Stereophile measurement of the Thiel CS3.7 here:
https://www.stereophile.com/content/thiel-cs37-loudspeaker-measurements
You can see there is a rather pronounce peak on top of the step response which means the tweeter phase is not well aligned with the rest of the frequency range, otherwise there would not be such pronounced peak. Again I don't mean to criticize here but more like trying to understand your definition of the term "phase coincidence". You definitely threw a curve ball into the conversation :-) It looks to me the tweeter phase is deviating from the frequency cross over point between the mid and the tweeter. John Atkinson would call this "phase coherent" and I would too. But then it appears that from your above post, you would disagree. If that is the case then it would imply the CS3.7 does not meet your criteria as "time coherent".