Thiel Owners

The ML 27.5 should be capable of driving the 3.7's successfully if not played too loudly in too large a room. More power could be beneficial.

Thanks unsound.

Andy - The Infinite Slope speakers are very good. His approach sequesters the phase misbehaviors to very narrow bands, so they are noticed very little, and the time misbehaviors are managed for least damage.  Previously you noted " how high frequency affects our hearing". The Infinite Slope treble reaches the ear ahead of the rest of the signal, and even though it does so in a well engineered fashion, that pre-arrival is radically different from natural sounds, in which the wavefront arrives simultaneously. The ear-brain is very good at reconstructing those elements into the alleged sound, but that takes work to do. Some folks prefer the wavefront to arrive intact. I am one of those folks, as are most of you on this thread. Thiel took the philosophical position that waveform integrity was important, regardless of whether the majority of listeners assigned importance to it.

By the way, source material, amps and ancillaries that work best with Thiel also keep those relationships straight. The low to no negative feedback designs such as Ayre, address the same goals with the same priorities as Thiel.

The Infinite Slope speakers are very good. His approach sequesters the phase misbehaviors to very narrow bands, so they are noticed very little, and the time misbehaviors are managed for least damage

Richard Modafferi, Infinite Slope designer, did claim that the group delay within the overlap region is very minimum therefore, at least within this region, the transition should not be a problem in the time domain. But as you said, there is still a problem of phase rotation in which the signal at 20KHz will arrive at 360 degree ahead of the signal at say 300Hz. But the other problem with steep slope is the rapid change in phase which will be addressed below.

From what I can gather so far, the high order suffers the following main two things:
1. As pointed above, phase rotation where high frequencies will arrive earlier than low frequencies and how much it depends on how the filter is designed. It could be 270 or 360 or 180 degree or somewhere in between . At the same time, I am not sure how sensitive our hearing is to this type of phase shift. Our hearing is not sensitive to the sound delay if this delay is within a few mlli second.  For example, at 17KHz, 360 degree would equate to 0.05 milli second.  Could our hearing tell of this small delay?  I mean with diffraction from the baffle, I would assume sound delay from baffle reflection could be more than 0.05 from various high frequency components.  On the other hand, at 500Hz, 360 degree would be 2 mill second which is somewhat close to our hearing threshold.  My conclusion is as at higher and higher frequencies, this type of phase shift may not something our hearing is sensitive to.  Thankfully, most xover even using higher order filter, do not have this type of phase shift issue at low frequencies.  And considering most xover crosses at 3KHz below which more or less covers most of the musical contents.  So regardless of xover, most of this type of phase shift will only occur at above 3KHz where our hearing may not be so sensitive.    

I have designed speakers that is first order time-coherent (no phase shift) and first order NON time-phase coherent.  The common denominator here is first order - but one is time coherent but the other in NOT time coherent.   The non coherent version has 180 degree phase shift at 20KHz.  BUT I had a hard time telling the difference in the sound quality or the intrinsic type of sound between the two xover types.   Although I do prefer the time-coherent version, but the frequency response and oxver point between the mid and tweeter are all different between these two version so I don't if most of the differences come from the time-coherence or because of different types of voicing. So where do I think the differences come from?  I think most of the differences that we have talked about will be because of #2 below.

2. All drivers have non-linear distortion which means the drivers will produce more extra frequencies than the frequencies putting in at the input. But why would this affect high order more than first order? I think because of of the rapid phase shift of steep filter slope, which in turn produces more over-shoot or more high frequencies energy vs. lower order filter with shallow phase shift. This extra high frequencies energy when applied to the non-linear distortion of the drivers, will produce more extra high frequencies contents that was not part of the original source. This extra high freq. will affect perception and it is consistent with what I and other (Prof) have observed that the treble of high order speaker seem to be riding on to of the music as if it is not part of the music but our mind will include it as part of the re-construction process. What I said above also implies that first order filter will suffer from this as well since it will inevitably have some overshoot (from parasitic such as drivers coils ...) but not to the same degree. This will also implies that if quality drivers are used which have low non-linear distortion, this problem will be minimized even with using high order filter.

#2 also explains why solid state components cannot produce treble as well as tubes (I won't try to go into much details), due to the nature of solid state physics, the electrons movement within the medium will experience high order filtering affect from parasitic, impurities and such. With tubes on the other hands, electrons only have to move in the vacuum from the anode to the cathode without having to go through any other medium therefore won't be affected by any filtering.  

And of course solid state amplifier does not have any xover that can explain the differences.  

Andy - you are puzzling it out. In the beginning, when we were wrestling with all these variables and making prototypes to compare A with B with C, we had some aha moments that led to the decision to tackle the 'real deal' . . . keeping the phase and time information intact - creating a coherent source. All the other approaches define ways and methods to minimize the importance of the time aspects of the hearing riddle.
Addressing time/phase serves to multiply the burdens of developmen -, it all becomes enormously more complex. Previously on this thread someone (?prof?) mused whether the Thiel Rightness is actually caused by phase coherence or rather the result of all the other details that were paid attention to in the designs. I say it is both. Coherence adds its own complexities and solutions, and it also demands that other details be very right or else they sound very wrong.