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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
asvjerry's avatar
asvjerry
4,389 posts
 
@andy2 ...*L*  Oh, goody....R/T 'engagement!  Or close enuff'...

I've been DIY'ing Walsh speakers for awhile now; not the current Ohm variety, but closer to the original F's and A's and the HHR in intent, But...

Size of the 'main' driver is larger than HHRs' smaller 'stand alone' driver and the German Physiks, covering the 'upper mids through upper bass'.

Hand off the lower bass to a sub...they're more efficient at it (and, MHO, most of the reason folks blew up the originals, due to cone collapse...) and bass being omni by nature anyhow...

High end:  a smaller Walsh, lighter cone, based kinda like the Infinity 'ice cream cone' driver of awhile back.  I've chatted with one who 'was there' in the creation of it, literally done on a kitchen table.  We've traded stories, both on and off topic... ;)

Tweet above main, vertical alignment.

I have working prototypes....working on Better.

"Be Afraid..." *L*  Not many have heard IRL....those who have, Like.

Any thoughts?
asvjerry's avatar
asvjerry
4,389 posts
 
I owned a pair of Infinity's with the ICC driver....pointed out that it was upside down on or in the cabinets.  The rationale for that was that they were too 'price driven' to mount them properly....

The only way you could hear them was to lay on the floor...
....which, back then, we did...occasionally....

SF in the early '70's....get the picture? *smirk* ;)
andy2 OP
1,539 posts
 
Any thoughts?
The Walsh and HHR and full range exotic driver stuffs you mention are a bit out of my depth.

And I am not familiar with some of the references in your post.

I am more into conventional cone drivers and speakers - like the typical Seas of ScanSpeak stuffs.

May be if you have a link that can show some pictures of your prototypes then hopefully I can chime in or maybe learn a few things.  I am more of a visual thinker.  


timlub
2,039 posts
 
@cousinbillyl 
You are correct about a lot of your phase conversations.... I spoke with Jim years gone by..... you might remember or go find up the thread where I said something like you can get a 1st order down to around a 15 degree phase shift??? that's what Jim did,  he did remarkable work taking a 90 degree shift down to 15 degrees.  
I won't argue,  but I will say that I've never seen absolute phase alignment between drivers without electronic crossovers. 
andy2 OP
1,539 posts
 
I won't argue, but I will say that I've never seen absolute phase alignment between drivers without electronic crossovers.
In my past experiences, most competent engineers will figure our how to "fix" it.  But the difference between a merely good engineer to one who can actually make money is that he understands the consequence of his "fixing".  

Ever heard of stories of a mad genius?  They all know exactly how to "fix" things, but nobody hires him because he'll end up breaking more things than fixing.

Hence I fear ... I fear ... I fear ... the electronic crossovers ... will they turn all my musics into mp3?  Will they cause mad hysteria and drive me to insanity?
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