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 ... :-)
Audiophile friend urged me to jump into this discussion with some of my ideas. Here goes my take on phase-coherent speakers and first-order crossovers: A perfect transition from an electrical signal to acoustic sound is defined by the simple so-called all-pass transfer function defined by: -St (1) f(s) = Ke (note: this dumb website does not allow math symbols, sorry)
For perfect fidelity in acoustic space this equation defines it, where S is the complex frequency variable S = p+jw and K,T are real positive constants and =2.718...... One can realize a loudspeaker crossover in Laplace-Transform form by expanding (1) in an infinite series and taking only the first term in (2) to yield (3), as: 2 (2) F(s) = e = 1/(1 + St + (St) + etc.......) Taking just the first term yields
(3) f1(S) = 1/ (1 + St) Laplace transform of (2) represents circuit consisting of a coil of T Henries in series with a 1-ohmresistor. (You need to imagine circuit because website cannot draw schematic symbols!) Replacing variable S with its inverse 1/S in (3) yields St/(1 + St) or, a single capacitor and resistor in series:
(4) f2(S) = St/(1 + St) Equation (3) is transform of a woofer crossover in circuit, equation (4) is transform of a tweeter in a crossover circuit. Now add (3) and (4) to obtain: (5) f1(S) + f2(S) = 1/(1 + St) + St/(1 + St) = 1. Sum adds to a constant, the number one! The crossover is perfect, a constant. No variables are present. Speaker will be flat in amplitude and linear in phase!!!! Crossover uses one coil and one capacitor!!!! Simple!!!!
Here I show why people are in love with first-order crossovers. Realized carefully, a first-order crossover system will work reasonably well and satisfy almost anyone with decent sound.
Contrast audio loudspeakers. Own designed parts. Only from naturall materials. Only single one capacitor in crossover-network! Frequency response of tweeter 10 KHz!
If to say about 3-band speakers, situation more interesting. WITHOUTT FILTEREDDD BASS DRIVER....
Perhaps he just tweaked it a bit further than a few others had.
I am sure he can do more than "tweaked". With a simple wave of a magic want, voila, a perfect speaker. If I were him, why do any work and just wave my magic wand.
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!
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.
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.
Hello Andy, Thanks for Interesting recent post. Both you and I find my results with invention crossover a mystery. Earlier infinite-slope crossovers worked nearly "perfectly" (maybe just OK) inside each other's band-pass, as characteristic to "brick-wall" filters make each other's loads (the drivers in speaker system) operate completely independent from each other. There is no acoustic interference among drivers in infinite-slope systems which eliminates "sweet-spot" errors acoustically. Amplitude response is flat all over listening space, dependent only on the polar response of each driver. However phase response is another problem which in my earlier work I either ignored or tried to fix with only slightly improved results. FFT analysis showed group-delay "bumps" at crossovers over a narrow frequency range around each crossover, I left things alone as an unsolvable problem believing error was inaudible. Many nears ago in Grad School during a course in acoustics I attempted to devise an experiment to determine if we were able to hear "phase" as we hear "amplitude". It became a difficult problem; I could not even devise a methodology to formulate an experiment which would result in useful data. I got a "B" for trying! Thus I became sure that we were "deaf" to absolute phase, or phase errors in reproduced sound over speakers. I know we hear relative phase in midrange very well with out 2 ears, as God designed us.(to avoid danger, etc.) However FFT analysis on my new invention reveals clean waterfall plots and seamless amplitude and delay at crossovers! I assume without proof that accidental combination of constant-resistance with infnite-slope compensates for "bumps" at crossovers. Everyone who listens to invention describes sound as "coherent" or "all-there", etc. Everyone listening for first time immediately states that they have never heard a speaker system sounding like real music as this one! Square waves maybe??? System test reveals good square-waves well over range 150Hz to 2.5Khz, at higher frequencies the 3rd and 5th harmonics become weak and waveform degenerates into sine wave. Square waves not too pretty having ragged edges due to edge diffraction from box.
A weak hypothesis regarding loss of group-delay "bumps" is somehow due to an adjustment of "overlap" at crossover frequency which compensates for delay bumps. Maybe you have an idea in this regard! If so your name can go on patent!
Hello Andy! I enjoy your posts. Thoughtful and intelligent; we are both music lovers and audiophiles. I need to explain again how I got myself stuck into giant speaker project as described in my very first post ever on any website, being forced into doing this by one of the four (now five!) audiophile friends who pushed me at age 81 (now) to jump into speaker design again. After retrieval of my notes from museum and study of topology (a favorite of mine from graduate-school network-theory courses) I tried a merger of "constant-resistance" network theory into my "Infinite-Slope" in my previous patents. First try was a 2-way series crossover at 2KHz. Installed this into Parts-Express 2-way speaker kit with test measurements in my home lab and also in anechoic chamber of Tech Center at Binghamton university. Waterfall plats, frequency-response, input impedance, delay response, all looked good, even surprisingly so. Even more so as I examined in detail match at the 2Khz crossover, it was seamless with no evidence of a "join" in either frequency or phase response. It was time to listen to music on this box and as in my earlier post, I burst into tears at first listen (I'm Italian!). Never in my life did I hear that kind of sound come from a speaker box! Emphasis needed here: I'm no genius. This result was a pure accident of discovery, nothing more, and certainly not expected. My audiophile friends came over for listen and forced me into building three Parts Express kits to listen to until I could come up with a 3-way crossover for their Joseph Pearls (Successful as mentioned in last post)! I should mention a funny effect I observe in audio showroom where we were comparing my invention with other speaker systems, as someone wanders in and after a few steps they stop dead suddenly at the sound! It happens every time one hears my invention for the first time. In closing I'm actually sorry I hit upon this thing, I nearly gave up and burn my notes and abandon patent, but it's too late; I need to see this thing through. Did a public demo of invention in August before an audience of 300 at a symposium with speakers as subject with incredible results (I hope to see this publicized in Winter quarterly journal of organization which invited me), one speaker manufacturer there asked me to try my invention; gave me data on their drivers. This is a Winter project ongoing. RIMO
The tendency of many high-end products to attempt to "fix it in the mix," as audio engineers would say (ie,
attempt to "improve" the realism of the original source material), is
not in the best interests of ultimate fidelity. For audiophiles who
value accuracy over euphony, products like the Dunlavy Signature SC-VI
loudspeaker are a breath of fresh air in a landscape polluted by
pretty-sounding panderers. Read more at https://www.stereophile.com/content/dunlavy-audio-labs-signature-sc-vi-loudspeaker-page-6#o2Rto2F348..."
Hahaha ..... I miss the good old days. A gigantic flag ship pair of speakers only costs $25K. Something like this today would be $80K. Nice square step response!
I would assume Infinite Slope filter would have higher phase shift using very steep roll-off slope filters. vs. a time-phase coherent design that uses first order filter which has the least amount of phase shift
It seems interesting that you posted with regard to the "Infinite Slope" in a time-phase coherent thread. It's quite a different philosophical design vs. time-phase coherent with respect to phase shift. I would assume Infinite Slope filter would have higher phase shift
using very steep roll-off slope filters.
vs. a time-phase coherent design that uses first order filter which has the least amount of phase shift. "Infinite Slope" advantage is minimal over-lap in frequency response between different drivers, whereas time-phase coherent is the complete opposite being having a large overlap. I suppose the disadvantage of "Infinite Slope" is the excess in phase shift?
I was wondering if you could share your opinions on "time-phase coherent" as to the extend it may affect on sound quality. Time-Phase Coherent insists that the phase of the system response (the overall response of a speaker) should be as close to 0 deg. phase shift as much as possible from 1Hz to 20KHz. Thiel design has claimed to achieve +/- 10 deg difference.
With "Infinite Slope", I would assume it would violate the criteria of 0 deg. phase shift. Would you share the amount of phase shift a typical "Infinite Slope" speaker. For example, what is the typical phase shift at 17KHz vs. to something like at 270Hz? For a time-phase coherent design, the phase shift should be very close to 0 degree.
Hi Richard, I have read your review on Parts Express several times as I find this speaker that you drastically changed a true bargain in the audiophile world. I look forward to hearing the results of your constant resistant technology combined with infinite baffle. Just curious, will your constant resistant technology work with any parallel or series crossovers? Please expand on this once you are comfortable with your patents. I appreciate you chiming in, Tim
Hello! I'm inventor of well-known (infamous?) Infinite-Slope crossover system currently marketed by Joseph Audio. My patent license agreement with them expired in 2005 and at that time I went into blessed retirement at age 67. In 2017 I was pulled out of retirement by three audiophiles owning Joseph Audio with the question, can your invention be improved? I said no but they insisted and I gave up to shut them up and returned to my notebooks (thankfully saved and in local tech museum) to study network topology and see if I have any new ideas. The major problem hinges on simultaneous realization of flat frequency response and uniformgroup delay in three-dimensional acoustic space of the listening room. Actually impossible but at least a good approximation is the best that we can do and I come close in with Joseph Audio's products as is well known. Mathematically one can achieve flat frequency response and linear phase (flat group delay) using a single very good 4" driver without crossover in a transmission-line box. This system will have nearly perfect performance over a limited frequency range and with limited loudness capability. Next, a 2-way first-order crossover is theoretically perfect in the math, but when realized in a speaker system, it is "perfect" only in the so-called "sweet-spot" where the sonic outputs of the drivers add correctly without acoustic wave interference. In 2018 at age 80 I attacked the problem again. With study of my notes, I came upon an idea which may work: Combine the idea (1) of so-called "constant-resistant" network theory with my already realized "infinite-slope" theory (2) (based on high-selectivity filters in radio circuits). I worked up a schematic-diagram of this new crossover idea using circuit-analysis models in a computer to start. The results looked promising, and at some month's work developed a 2-way crossover model in virtual cyberspace having both optimum frequency and delay responsesimultaneously! Now it was time to build a physical crossover and try it in a prototype speaker system and found a quick-easy way to proceed:
I ordered the so-called "Solstice" loudspeaker kit from Parts Express , built kit, and installed my 2-way prototype crossover. At first I did not expect anything unusual, just another pretty-good sounding speaker system. I fired up my test equipment and made frequency, phase tests, and determined that system had good frequency response but surprisingly, flat group delay above the cabinet bass resonances! A trip to the anechoic chamber at Binghamton University's Tech Center confirmed my measurements. Now it is time to listen!
Played a CD of John Pizzarelli "Dear Mr. Cole" and the sound hit me so hard I burst into tears!Never have I heard sound like this from a loudspeaker box! The room disappeared and I heard the band! Switching to my Pearls, I heard a good loudspeaker system. Now time to call my pesky audiophile friends, do listen with everyone astounded! We all hear something magic! I, almost with accident, had hit upon something unexpected! We repeated test of my prototype in audio showrooms with three listeners against systems in the $30,000+ price range with same results, the little 2-way prototype was clear winner having obvious easily-heard sonic improvement. There was uniform spectral-energy sound throughout the entire listening space, with uniform sound without "sweet-spot" with all hearing music coming from a nearly perfect "orchestra" instead of a set of speaker boxes.
I had to develop (successfully) a 3-way crossover so invention could be installed in Joseph Pearls, with the same astonishing results. Stay tuned everyone! Patent on invention filed July 2019.
Timlub, I appreciate you sharing your knowledge on this vexing aspect of audio. I can't say I understood it all, but it greatly aided my background on the topic.
Roy at Green Mountain Audio was a big proponent of time alignment of the drivers in this speakers. He also advocated removing ones eye glasses when listening to speakers because of the "smear" ? that they caused in aural perception. I built a pair of Linkwitz LXmini's a few years ago, before they came out with the companion subs for them and they were pretty sublime, but rendered my expensive 2-channel amps unusable and had limited LF response.
I remember in 1983 when bought a pair of Spice TC50's. I was casually listening to them one night when my neck and attention snapped to the left of the room when some violins started playing on the track... the imaging was simply unbelievable, palpably realistic. At the time I listened to music at pretty high SPL's and went through several woofers and tweeters before moving on to JSE Infinite Slope speakers from Jeff Joseph. They imagined quite well too, but not like the Spica's. The Spica's were like electrostatics with a very narrow sweet spot.
Look, I'm not out to dog you to hell and back. I'm not asking you to change your style or anything...just try to be just a Little more respectful of everyone else's point of view...maybe even if you don't entirely agree...maybe offer a civil but rational response that might explain your objections in the terms they presented??…just a little more give and take maybe??
Yeah, why don't you're out of this universe if you know what I mean. Some how I doubt it. I'll probably have to deal with your shenanigans sooner or later.
The way you treated me I could expect, my problem was with the way you treated everyone else here.
Like about everyone else in this thread before me has figured out and gone (where are they now), you're long on making a splash and short on contributing anything useful. There were plenty useful comments here to make a good thread out of, but you were only interested in what you think you know, as others tried to tell you.
But, for everyone here and any exchange of ideas, you were too much of a headache and too much of a PITA...I'll leave it to you as to how that pairs up.
Most of the better systems I've been around are such. It makes sense to cope with the signal on a lower level before adding 'power'. Better and more discrete control without having to cope with high drive levels.
The same holds for active eq; I can 'adjust' for my space, even with omnis. I can 'ignore the room' so to speak, since I'm in the midst of it.
I know I'm ignoring most of the past posts...but I'd rather cut to the chase. MHO.....and please, 'humble' is the word of the day....well, this evening here. *G*
...and I'm now quite happy to be on the other side of the country... *G*
Anyway...calm down, stay on topic....
I came back 'cuz you started a topic that got my interest, and that of others. I/we don't mean to make you feel attacked, far from it. Phase issues, which you yourself stated earlier are complicated.
Resorting to 'quantum states' ain't gonna help us typical audioholics, no. I'll return to my last aside that active xovers may cure the bulk of the issues. Give the drivers what they Need 'upfront', so to speak.
Yes, it requires bi-, tri-, or whatever amping quantities required... ....but it sure works in my space....
Well, I suppose I'm tired already of the ramblings of an 'educated' man who can't think his way back down to earth long enough to answer his own question...ya got me there I guess.
My hat's off to you, if you can fly as high on yourself as you claim to and still not know how to fix your problem.
I'd say your first blow up in your thread 'started' it, you just snowballed from there.
He started it. I think he intentionally tried to piss me off so I’d give him some bread :-) Hey self defense and gun ownership are still alive and well.
So desperate! I figured since you're probably a high school drop-off, I'll start with "stupidity" first lols. Then maybe go somewhere from there. After that I'll work with you to make you feel less pathetic. I feel ashamed for you, I really do.
"You can’t be so desperate, can you? Are you saying "stupidity" is what you’re waiting to save you?"
Uhh...No. That refers to your wanting to berate or challenge anyone who is not answering your questions, particularly the unanswerable (what does it sound like), to suit your impatience, and then getting irate at the answer when it comes. You’re acting a bit like a drowning man who’s spitting at anyone who tries to throw you a life preserver. That’s pretty stupid, even for a forum.
But, if you’re saying that’s not stupid for you, then I’ll take your word for it...I guess.
Yeah it’s Friday. And tomorrow’s Saturday and the next day is Sunday...I for one, don’t especially care how long it will take you, or how old you will turn out to be, before someone ’Finally’ leads you by the hand and delivers you (and the rest of us) from your own stupidity.
You can’t be so desperate, can you? Are you saying "stupidity" is what you’re waiting to save you? If that’s the case, can you jump off a building somewhere lols? If "stupidity" is what you’re waiting for, well just go and say "Hi" to whoever closest to you. That should give you a quick "stupidity" fix.
I got more poetry for you. More "stupidity" for you every week. Chew on that brother.
@andy2 looks so far like you’ve come to this thread demanding some answers (you keep flailing away at the one practical-based q[what does it sound like?]). It’s one thing to want answers, everybody in this forum does, but it’s another to just plop down in a thread and bitc# and moan and blame everyone else for the fact that You don’t understand something, like we’re supposed to think you’re ’spatial’...you seem to think that Your ignorance is somehow Our fault.
You probly would’ve had more support if you had accepted responsibility for that from the start, but you evidently decided in advance that all of us are b@stards from the start for not telling you what it is you want to know.
I think at this point someone could give you the answer you’ve been looking for all along and you’d have too big of a chip on your shoulder and be too stupid to recognize it. Personally I have no interest in whether or not you ever do recognize it...and I don’t think anyone else here should either.
Yeah it’s Friday. And tomorrow’s Saturday and the next day is Sunday...I for one, don’t especially care how long it will take you, or how old you will turn out to be, before someone ’Finally’ leads you by the hand and delivers you (and the rest of us) from your own stupidity.
a careful study of the ten or so first principles that go into Vandersteen speaker design will illuminate why time and phase are just the start. You could explore the just expired patent on the aerodynamic low reflection driver for starters, or perhaps the shared Low/ Vandersteen patent on DBS, which is applied to the internal filters for the 5a or the pistonic CF/balsa core midrange which is a trade secret, or cabinet within a cabinet, or the co-cured Cf stealth cabinet, etc....the list is long, since 1977
Thiel slanted their cabinet face for time coherence. Tilted Sound Anchor stands do the same thing. It makes the sound from the drivers reach your ears in closer time phase. Think about this: The electrical signal reaches the deep-in-cabinet woofer magnet at the same time as the mid-sized mid-range and shallow tweeter. By aligning the magnet centers, the sound from the tweeters does not reach your ears before the mids, which is ahead of the woofers. Amazingly, some people use tilted stands with internally phase aligned positioning of the drivers, making the alignment bass ackwerd. Panel speakers do not suffer from alignment issues, for obvious reasons.
Actually, we and other apes evolved from several ape-like critters, not only one. As far as phase coherence, having grown up with B&W from the beginning, I saw that their original test equipment demonstrated that what was measured by lasers reflecting from the drivers, when compared to the electrical signal, became more coherent when the drivers were time aligned. I measured my sub driver and aligned the center of voice coil magnets with my B&W 803 magnets. It does work, but phase alignment alone does not make a speaker out of a cow's ear. Also, if you are getting a lot of wall reflection, your question is moot.
Forgot to add that I have really liked some of the Vandersteen speakers I have heard over the years. To this day I think they make superb lower cost speakers. Hated the older Thiels to a large degree because of the tweeter he used.
I think bdp is correct, no truly full range driver has been invented. However I have heard some lately that gave me pause and so completely eclipsed what was available even a few years ago.
Experience the insane imaging of a Vandersteen Model 7 and you will become a believer in time and phase coherence.
Although I am an proponent of time-phase coherence, I can't conclusively say that the reason the Vandersteen and the Thiel are so good because mainly because of time-phase coherence. I guess I am not fully convinced until I know for sure. From a theoretical stand point, time-phase coherence is better, but a speaker has so many variables that it's hard to pin down which is the most responsible for the "goodness".
I am sure a lot of people would be impressed by the various Wilson high-end models but they are not time-phase coherent.
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