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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
1,539 posts
 
When I look at this thing I dont know if I should laugh or cry.
Ultimately it all ends up in "cry" like the "Crying Game".  But I give that it helps to laugh every now and then.
andy2 OP
1,539 posts
 
You can Google and find photos of this crossover
OK, just did.  Actually they don't look that bad.  It all depends.  


bdp24's avatar
bdp24
9,547 posts
 

As Danny Richie (GR Research) explains in his series of excellent You Tube videos on the subject of loudspeaker design, cross-over design is a matter of getting the individual drivers to coalesce. He uses the waterfall plot as his number one design tool, as it reveals a LOT about what the drivers are doing, both in amplitude and phase, which are inter-related.

The phase responses of the drivers in a speaker is a major component in that speaker’s frequency response. The summed output of two drivers which are out-of-phase at any given frequency cancel, creating a null, and a resulting depression in the frequency response. Listening to Danny discuss a speaker which uses two widely-spaced tweeters to reproduce the same frequency is pretty amusing. ;-)

audition__audio
1,394 posts
 
Yes getting to get the drivers to coalesce using the simplest and most efficient method possible which presupposes using the fewest crossover components. Amplitude and phase are very important but even the best crossovers just minimize the damage. It is impossible to solve amplitude and phase problems when a crossover is present in the design.
bdp24's avatar
bdp24
9,547 posts
 

Unfortunately, a full-range driver has yet to be invented! Big ESL’s are close, though. The best we can do for now is use two or three drivers integrated with filters designed to make them behave as one.

Danny Richie has designed loudspeakers in which he used the NEO3, NEO8, and NEO10 drivers in an open baffle frame. All the NEO’s share the same sound characteristics (unlike the drivers in most multi-way dynamic speakers), with each driver covering a different range of frequencies (each driver’s dimensions determining it’s optimal frequency band). He then created filters that combine their individual outputs into a cohesive whole. He mated them with OB/Dipole subs for very full-range music reproduction.

Nelson Pass is a single-driver loudspeaker proponent---watch the You Tube videos made in his listening room to see his. By the way, Nelson has created active analog x/o filters for the OB loudspeaker designs of his good friend Siegfried Linkwitz (R.I.P.), a true master of loudspeaker design. Nelson’s analog x/o’s are used in place of Linkwitz’s stock digital ones.

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