Thiel Owners

thosb
Thank You for the cable update. Good to read that Acoustic Zen (AZ) was an upgrade over Audioquest (AQ) for your system.  Acoustic Zen, Audioquest, Belden, Blue Jean Cable, Cardas, Dueland, M.I.T., Synergistic Research (SR), Transparent Audio (TA), are all sonic matches for Thiel speakers. Across the various Audio forums, I am sure there are other brands represented as well. At any time, feel free to discuss cabling options, because we all hear differently.
Happy Listening!

When it comes to first-order coherent and non-coherent, there has been some misundertanding with regard to the step response. For non coherent speakers, invariably, the polarity of the different drivers will be different, that is the tweeter may be inverted polarity and the woofer will be positive polarity. Therefore in the step response, the tweeter will "APPEAR" (notice capital letter for emphasis) to go negative with respect to the woofer. But that misses one subtle but very important point that will lead to a crucial insight to the phase of coherent vs. non coherent design.

Most people came familiar with step response measurements by way of Stereophile John Atkinson measurements, but his measurements only show the overall step response without the measurements of each single driver. Once each single response is shown, there is further truth to be gained.

I will use one of my project to illustrate the misunderstanding. See pic of speakers here:

https://www.flickr.com/photos/185616271@N05/49106259616/in/album-72157711891600612/

Below is the xover design. Notice the tweeter is inverted polarity and the woofer is positive. Also notice the step response on the lower right corner. Also notice the phase of the speaker response on the upper right corner of the plot. That is the phase starts at about 0 degree, and gradually go to -180 degree. Also notice each individual component freq. response and the cross over point.

https://www.flickr.com/photos/185616271@N05/49106444352/in/album-72157711891600612/

At first glance, the tweeter seems to go completely opposite of the woofer (the initial dip of the step response). The time-coherent proponent will say – wait a minute, that’s all wrong since how can the treble be completely opposite of the woofer? But that is not quite right. The tweeter ONLY opposite of the woofer at very high frequencies, but at low frequencies, below the xover point, the tweeter and the woofer actually go up together.

I here have a zoom in pic of the step response. You can see the tweeter and woofer go up together after the initial high frequencies. It’s subtle but it’s there and it’s very important.

Green – system

Red – tweeter

Yellow - woofer

https://www.flickr.com/photos/185616271@N05/49106444417/in/album-72157711891600612/

What does this mean? If you look at the frequency response below, you see that the phase of the system is only at -180 at 20KHz, not the entire plot. But below the xover point, the tweeter and woofer are more or less “in-phase”. For example, at 2KHz the phase is only at -60 degree, at 3KHz the phase at -80 degree. As I said before, since our perception is not very sensitive at high frequencies, most of us may not “hear the difference”. Most of the musical contents occurr below the xover point which is about 3KHz in this case and that’s where most of the phase shift has not occurred.

Also the phase change is not at a constant -180 degree everywhere but only at exactly at 20KHz. For example, the phase change at 20KHz is only a few degree vs. 19KHz and likewise 19KHz is only a few degree vs. 18KHz … and so on. It’s a gradual shift in phase so our hearing may be able to adjust to it.

But on the other hand, if this -180 degree occurs at 500Hz, trust me, you will definitely HEAR it!  I think high order can get away with it because the phase shift occurs at high freq. where our hearing may not be so sensitive.

https://www.flickr.com/photos/185616271@N05/49106492271/in/album-72157711891600612/

So how does an ideal time-phase coherent design look like. Below is a design using ideal perfect driver. Notice how the phase of both the tweeter and woofer tracking each other at 90 degree apart. But the overall phase of the system (the green curve) is at exactly zero.

https://www.flickr.com/photos/185616271@N05/49106060213/in/album-72157711891600612/

But real world system does not look that clean and the phase is not going to be exactly at 0 degree. I’ve modified the xover so the tweeter and woofer are all positive polarity, and the phase of the speaker stays more or less within 0 degree (the green curve). Notice the step response where the tweeter and woofer go up together.

https://www.flickr.com/photos/185616271@N05/49106502197/in/album-72157711891600612/

Andy - the term of art: Phase Coherence is used in various ways by various people for various purposes. Thiel was a pioneer in Coherence along with Richard Vandersteen and John Dunlavy. We all use the term to mean Phase Coherent and Time Coincident. In other words all the elements of the signal launch and add together to produce the step response of the input signal with no negative pre-shoot at any frequency. Very simple and very difficult!

Phase Coherence is used in various ways by various people for various purposes.

I understand.  I am personally got lost with all the different terminologies. 

Very simple and very difficult!

Being working on DIY, it usually takes me much more time than a typical high order speaker.  But still, I hope more speaker manufacturers will do it.  It may be very difficult but not impossible.  
I think it's just an "excuse" that most people won't try it. 

I was thinking about how our hearing may not be so sensitive to high frequencies and the high freq. phase shift.  In our normal environment, high freq. is very reflective and when sound reflects, its phase will get change as well.  Also diffraction will cause delay in high freq. and phase shift as well.  If human is sensitive to these, it would drive us crazy. 
That's why our hearing is only sensitive to long delay, not short delay, and the long delay we hear is what we call "echo".  Imagine if we listen to high order speaker and we hear all "echo", I guess that would not be very good :-)

But having said all that, I still think time-phase coherent could make a difference, and if I could, my speaker would be all time coherent.

Since the issue of tubes driving Thiels has come up, I want to add a bit of experience.  When I first bought my 3.5's, I used an Audio Research D90, and volume was never a problem.  Later, in a much larger listening space, I used VTL ST-85s, and again volume was not a problem.  I must caution, however, that when I say "not a problem" I am talking about jazz, chamber music, 60's-70's singer-songwriter, etc.  I do not generally listen to hard rock, and while I play fully symphony orchestras I tend to keep the playback at comfortable levels.

I also will relate that when I obtained my 2 2's, for about a year I drove them with a Fisher 202 integrated tube amp putting out 35wpc.  Again in an average size condo living room and at reasonable levels.  (This combo sounded fantastic, btw).

Take this for what it is worth.  But I guess it puts me in the camp of Thiels are okay with tubes.