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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
atdavid
736 posts
 
I think your conclusion w.r.t. filters may be a wrong conclusion based around the type of filters you were using. Different filter types have considerably different step/impulse response, independent of order.
You also have to accept that nothing in nature has 0 mass and infinite force so this concept of a pure step response is theoretical.


Add in some confusion from the likes of MQA and minimum phase filters in DACs which provide what could be considered an artificial output, i.e. they create something from the music that did not actually exist, and .... well draw your own conclusions. It is more a discussion at that point of euphonics ... what people like, not what is accurate.

Just sending a sound through air softens an impulse response. If you are recording an instrument really close to it, then adding the above minimum phase filters, you could create a very artificial response akin to having your speaker right next to the instrument, not the typical 10-10’s of feet away. What is even "natural" at that point?
simonmoon's avatar
simonmoon
594 posts
 
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.

Not to derail the thread, but I just can't let an ignorant comment like this go by without comment. 

We did not evolve from chimps, humans and chimps (and other modern apes) evolved from a common, ape like ancestor.

The idea of a 'missing link' is archaic. There are many transitional species between ancient apes and modern humans. 

There are mountains of evidence: genetic, fossil, comparative anatomy, homology, and much more. 

Carry on...
andy2 OP
1,588 posts
 
There are mountains of evidence: genetic, fossil, comparative anatomy, homology, and much more.

Carry on...
You really took it seriously did you?  I look more like chimps than apes.  
andy2 OP
1,588 posts
 
I think your conclusion w.r.t. filters may be a wrong conclusion based around the type of filters you were using. Different filter types have considerably different step/impulse response, independent of order.
I actually I never said that.  Or maybe you've read my mind but wrongly :-)  I don't even know the meaning of that statement above you wrote there.  Kind of like when the judge asked me "Did you see that girl".  I was like "What girl are you talking about?"
atdavid
736 posts
 
You stated that "why time-phase coherence is only possible with a 1st order filter" ... I was filling in the blanks.

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.

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