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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
 
A lesson? High end expensive stuff from companies with sufficient depth to design and program signal processing electronics, i.e. like Harman companies, are doing high end in digital. They may not be making $100,000+ speakers that way, but that is mainly because that is not their market.
They are things you can do in digital signal processing that literally cannot be done in the analog domain. There are aspects of dynamic speaker correction that can be done in digital firmware that cannot be done in analog, and when you start talking about more sophisticated multi-driver speakers, that just compounds.

High end analog speakers are a market, but not the epitome of what is possible. That will only come with advanced digital signal processing techniques.
andy2 OP685 posts10-30-2019 10:03pm
There is still some or even a lot of reading on digital if you want to start pushing the limits / doing custom FIR filters, etc.
Digital is for low end stuffs. High end and expensive stuffs are pure analog. Consider it a lesson.


andy2 OP
1,538 posts
 
High end expensive stuff from companies with sufficient depth to design and program signal processing electronics, i.e. like Harman companies, are doing high end in digital.

That’s not I see in REAL life. Most of the most expensive speakers on the market are analog. I can only speak with real life examples. Sure with imagination anything is possible. There are a few digital stuffs but they are few and far in between and hi-end market does not take them seriously. Like Ferrari or Porsche or Lamborghini, nobody wants to drive an electric supercar.
andy2 OP
1,538 posts
 
You can literally be an armchair speaker designer with digital. I've always said that anybody can do it.

Well anyone can smoke pot, but it does not mean anyone should do it.
timlub
2,039 posts
 
Andy, you have shown in your comments that you have a VERY LIMITED KNOWLEDGE. A decent active crossover in knowledgeable hands will crush the performance of a top tier passive crossover. Maybe you should explain what time phase coherence is from your point of view so that we can properly respond. So not to waste your time again. I was talking about time and acoustical phase alignment and how they are effected by the electro magnetic structure of a driver as well as the parts chosen in the crossover and the order of crossover design itself. Active designs make much of this benign and allows correct time and phase alignment with steep slopes. 
ivan_nosnibor's avatar
ivan_nosnibor
1,047 posts
 
"There is still some or even a lot of reading on digital if you want to start pushing the limits / doing custom FIR filters, etc.
Digital is for low end stuffs. High end and expensive stuffs are pure analog. Consider it a lesson."


That used to be true, but that particular part of the landscape may be changing. The only true weakness for digital (as long as it has all the proper inclusions of capabilities, which don't they always have) is the sound quality. That's been true of CDP's, DAC's and everything else digital...only there, sizeable advancements in sq have been made through power treatments. And digital crossovers should not be left out of that picture. Power treatments, particularly the quantum kind (which don't have all the weird side effects that component-based [caps, transformers, or other parts] power conditioning does), are beginning to change the game in favor of digital in general. It adds to the cost, but it compares extremely well to the best analog, when done sufficiently well.

"With digital actives, you just dial it up and listen for yourself...a whole lot easier and faster that way.
When someone claims something is "a whole lot easy", I go like "hello, what has he done?""


I'm talking about sitting in your listening chair (with at least a mockup of the speaker design in front of you) and then going through the listening/evaluation trials of whatever drivers-vs-crossover recipes you might want to investigate...maybe make some measurements with Omni-mic to confirm some things and you should have most or all of your answers right there...the process shouldn't even take you one, whole day to test, if all goes well. You may not be able to actually measure, say, the waterfall plot of the finished design (I suppose you could if had the right test gear), but you might be amazed at just how far down the road this will take you toward a solid, finished design in one take. I tend to go through this same process several times on different days so I can average out my own moods, predilections for listening for different traits, listening awareness levels and so on, in an effort to help me take my own fallibility out of the equation. But, you get an excellent feel for things like step-loss issues, phase issues, dispersion and all the rest of it, all at once. I used this process to design a pair of open-baffle stand mounts, which are not hard to build anyway, but if you're looking to build some giant-sized box, then you would have to make a good enough mockup to listen and test with.
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