Thiel Owners

@tomtheil Not to put too fine a point on it [although it seems I did!], but I have most of the hardcopy 'glossy' marketing brochures for 2.3, 2.4 and the 2000s entire Thiel line.

The 2.4SE brochure's lead headline under "Features and Benefits" is "Completely Time and Phase Coherent" and repeats that in the text.

A text printout of the CS2.3 web page states "As with other THIEL speakers, the CS2.3 achieves complete time and phase accuracy for very realistic ...".

The CS2.4 brochure in the center section of bulleted features "Completely time and phase coherent for greater realism" and repeats the same sentence in the headline of the text that repeats it again and its benefits.

A four page glossy full-line brochure from 1/2011 makes the same statement at the top of their bulleted features, as does the CS2.4 "New Product Press Release."

So perhaps the marketing folks took liberties that Jim would not have approved of personally and technically?

I'm uncertain what you mean by the "phase shift problem evaporates" when the "bass extends below the program limit." What is the 'program limit'? There's essentially no 'real' bass below my 2.4 passband of 33Hz. It's the range between 33 and 100Hz that the radiator is fully active that it seems there is the phase shift.

Please don't anyone take this as a critique, only critical thinking. Just in the last few days I've reconfirmed how the relaxed and lifelike presentation of my 2.4 exceed all the lesser benefits of my recent KEF LS50 Meta purchase, and put them back into the big rig indefinitely.

sdecker - I appreciate your feedback. Remember that I did not keep up with Thiel for its last 15 years. I agree "completely time and phase coherent" is a marketing, rather than an engineering term, so it would have come through Kathy's channel. Fair point.
On the other hand, excepting that stuff in the bass, those speakers are phase coherent.
What I mean by the "phase shift problem evaporating" is not clear to me either. My measurements show group delay remaining constant through that 33 to 100Hz range, and I don't have a handle on what frequency the full rotation occurs to cause the lower fundamental to be be behind the upper range. I'm not being coy, I'm admitting my limited knowledge of the particulars. I do believe the effect is audible, if we compared your 2.4 to a CS5. So much to learn, so little time. Please educate us if you learn more from the Asylum or other study.

It is my understanding that a 360 degree phase rotation has no audible impact. The audible impact of a phase shift is more likely if the drivers interact and deviate from the baseline phase. My measurements of individual thiel drivers show remarkable near zero phase of the main frequency range of each driver but the xo range usually needs work. As the xo range is wide, this is a challenge. I was not able to validate that the cross over filters cause the cancelling out of the opposite phase effects. I don't know if this is a result of variation in the speakers and/or the limited sample size. What I do know is using digital linear filters is able to come close to the ideal and maintain near zero phase in the xo range and if carefully designed can keep any pre-ringing to a minimum. Comparing the near zero phase speaker with the variable phase speaker seems a subtle audible difference at best. 

Happy Friday! All

thielrules - as I see it, the output of the port is a full cycle behind the output of the upper drivers, with 4th order (24dB/octave) slopes induced by the physical / mechanical interaction of the resonating port (no electronics involved.) Since I think that 4th order slopes maintain phase linearity, the only non-coherence would be in the time domain, where the frequencies covered by the port would emanate one cycle behind (but in phase). My calculation says that lowest tone centered on 38Hz (port peak output) would sound like it comes from 30' behind the speaker.Above 50Hz (the -3dB/half power crosspoint) the output becomes dominated by the woofer which is in-plane and therefore in-time with the upper signal.

The lowest note of a bass is about 40Hz, and most of its information is above that 50Hz crosspoint. So, I'm not surprised if many people can't distinguish between ported and sealed bass. Also, your DSP solution that further minimizes slight phase discrepancies in Jim's original analog filters, does introduce a digital conversion as well as some pre-ringing (which you have minimized.) I am one of those folks who is sensitive to pre-ringing, so I might choose different trade-offs than you do.
Remember that most modern speakers admit these 360° / full rotation phase shifts at every crossover point, where there is lots of musical information. The common call is that "it can't be heard". I suspect most Thiel fans prefer it not be there, even if their ear-brain is deemed to be able to ignore it.