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First order/Time Phase-Coherent speakers discussions

"The game is done! I’ve won! I’ve won!"


I would like to use this thread to talk about this subject which I find rather fascinating and somewhat difficult to get my hands on. I went through a course in electromagnetism in college and I have to say this is even more confusing and you won’t find the answer in calculus, physics, Einstein relativity be damned it’s not in there either and definitely not in quantum physics. Listening to the "experts" from Vandersteens and Stereophile but ultimately it all came down to a missing link sort of argument ... something like this:
"Since if a speaker can produce a step response correctly, therefore it is time-phase coherent, and therefore it must be "good".

It’s like saying humans come from chimps since they share 90% genetic content with us, but we can’t find any missing links or evidence. FYI, we share a lot of gene with the corn plants as well. Another argument I’ve heard from John Atkinson that lacks any supporting evidence and he said that if everything else being equal, time-phase coherence tends to produce a more coherent and superior soundstage, but to the best of my knowledge, nobody has been able to produce some semblance of evidence since there is no way to compare apples to apples. Speaker "A" may have better soundstage simply because it’s a BETTER design, and the claim "time-phase coherent" is just a red herring. There’s no way one can say the "goodness" from "time-phase coherence" because you can’t compare apples to apples. Ultimately it’s a subjective quantification.

I’ve been doing some simulation and I will post some of my findings with graphs, plots, actual simulation runs so that we are discussing on subjective personal opinions. Some of my findings actually shows that intentionally making time-phase may result in inferior phase problem and NOT better! (will be discussed more in detail).

Having said all that, I am actually in favor of first order/time-phase coherent if POSSIBLE. I am not in favor of time-phase coherence just for the sake of it. It’s just that there are a lot of mis-information out there that hopefully this will clear those out. Well hopefully ...

Here my preliminary outline:

1. My "subjective" impression of what is "musicality" and how it’s related to first order filters.
2. Interpretation of step-response. I’ve read a lot of online writing with regard to the interpretations but I think a lot of them are wrong. A proper interpretation is presented with graphs and simulations.
3. A simulation of an 1st order and higher order filters with ideal drivers and why time-phase coherence is only possible with 1st order filter. This part will use ideal drivers. The next part will use real world drivers.
4. A simulation with actual drivers and how to design a 1st order/time phase coherent speaker. Discuss pros and cons. And why time-phase coherence may actually have phase issues.
5. Discuss real world examples of time-phase coherence with Thiel’s and Vandersteens speakers (and why I suspect they may not ultimately be time-phase coherent in the strictest sense).
6. I’ll think of something real to say here ... :-)
andy2
andy2 OP
1,555 posts
 
Hi Richard,

Thank you for your posts and your unique perspective. For now, I would like to take a rain check as for a proper response from me since it may require a bit more thinking from me.

The only thing I want to say now is that, after listening to different types of speakers with different design philosophies, some being optimized for freq. domain and some being optimized for time domain, I think a well designed speaker all sound very good regardless of the underlying design philosophy.

Some one once told me all women are beautiful. If she doesn’t look beautiful, it just means that she does not know how to put on make up. Same with speakers. If a speaker does not sound good, it probably because it was not well optimized for its purpose - however different in design philosophy.

I would like to stop for now, but without trying to sound too general, I think ultimately, either you gain in frequency domain or time domain but at least for now, I don't know of a way to have both.  God does not seem to give us human any free lunch.  


unsound
7,336 posts
 
^ https://www.stereophile.com/content/dunlavy-audio-labs-signature-sc-vi-loudspeaker-specifications

…"...Frequency response: 25Hz-20kHz, +/- 0.5dB (approx. -3dB at 20 Hz)."...
prof
3,485 posts
 
Well, Richard's input in to this thread is fascinating!

I personally have nothing technically useful to add, just personal anecdote.

I own both Thiel speakers (had the 3.7s, now own the 2.7s), with their concentric drivers and time/phase coherence, AND I own the Joseph Audio Perspective speakers (Infinite Slope).

The difference I hear between the two designs is that the Thiels have an imaging precision and density none of my other speakers have ever had, including the Joseph speakers.  They "disappear" just that much better than most speakers, but without sounding ghostly or insubstantial in the imaging.  Tonally they sound very "right" to my ears.  And I would but the Thiels as the most coherent multi-driver speakers I've ever owned (or, I think, heard).

The Joseph speakers though seem to offer even lower apparent distortion in the signal, with a sense that a fine layer of "hash" heard in most speakers seems removed, so the timbral quality of instruments seems even more revealed.  (They are also very punchy and fun and image/soundstage great!).

As for other time/phase coherent speakers, the old Dunlavy's also impressed me, doing something very similar to my Thiels.

And yet, having also heard the newer Kii Audio Three speakers a couple of times (DSP speakers time/phase coherent), I didn't find they had the same magically believable tone as I hear in either the Thiel or Joseph speakers.   I found myself having to "work" to unravel various instrumental timbres in the mix, where with the Thiels and especially with the Joseph speakers, this is effortless.   Don't know why.


andy2 OP
1,555 posts
 
So it looks like the Dunlavy Audio Labs Signature SC-VI was designed by God after all.  Only HE can give us the cake and we can eat it too.  Perfect time/frequency response!  
unsound
7,336 posts
 
^ Perhaps he just tweaked it a bit further than a few others had.
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