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 Not sure that there is a question here. I've run many simulations with 1st, 2nd, 3rd and 4th order slopes. I've run many comparisons with butterworth and linkwitz riley in 2nd and 4th order.
Even putting a single cap on a part does not ensure that you'll end up with 6db per octave. And really isn't the closest thing that you can get to proper phasing coming all the way around with 4th order slopes? 1st order are normally at minimum 15 degrees out of phase. 4th order can be very close. I'd recommend physically time aligning your drivers then comparing your slopes. I've had surprisingly good results in soundstage and imaging running odd order butterworth (say 12/18) as well as linkwitz riley 4th order. Both of these solve issues with driver peaks also. again not sure that these comments are what you are after, but I hope they help, Tim
I agree with what you said. Putting a cap on a tweeter for example does not mean a first order 6db/octave. The best I can hope for is 6db/octave in a limited frequency range. I think speakers from Thiel and Vandersteens that "claimed" to be first order, but it's an approximate, but I don't want to say too much here. And as you said, there are more than time-phase coherence. There are many ways to design a good pair of speakers. And I won't argue personal preferences. I will present an "objective" point of view: here is what first order/time phase coherence. Whether which one is better is not up to me.
I took me a lot of works and a lot and lot more thinking to put together what I think is a comprehensive and meaningful discussion of first order / time phase coherence approach that I don't think I saw anywhere on the web. As I said, there are just too many misinformation out there. Some people ought to pay me lols. It costs me a good life!
Also I am not really looking to argue with anyone here. I will present my case, and it's up to you. I suspect more will end up disagreeing with me than agreeing :-)
Time cohesion is a myth. If the tweeter was hundreds of metres behind the woofer then youd hear a delay. The actual distance involved is within about 1cm so obviously theres no delay that can be heard.
Funny ... I really have no idea if there is such a thing as a "better" speakers. From personal experiences, designing first order speakers is really hard and it usually takes a long time vs. higher order speakers. This is not a subjective observation or myth lols, but a matter of fact since since I think I am capable enough to tell the flow of time ... by counting my gray hair :-)
Usual things that are hard tend to be good. A beautiful hot blond is not going to say "yes" so easily. Ask me how I know. Oh well maybe I should stick with higher order speakers ... hahahahaha
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?
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?"
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.
OK, I don't think I should be responsible for someone else's words.
Are you saying time-phase coherent is possible with higher order filter? I suppose you could come up with your own definition of time-phase coherent but then anything is possible then.
As someone has already done the work, I will simply post that from John Bau. By done the work, someone who has a product on the market and advertises this is what they do. It is not such an advantageous marketing thing these days. And that is only simple analog domain in the cross-over. With a digital active cross-over, time/phase alignment becomes relatively easy.
you really have a lot of homework left.... you can't figure phasing without understanding the drivers being used and how slopes and parts will affect phasing.... it has not been mentioned, but remember there is acoustic phasing as you have been discussing, but there is also electrical phase. The rare time that I see that mentioned here on Agon is when discussing using tubed amplifiers, but individual drivers can vary phase when you change crossover points or slopes or even part grades when it comes to coils. Most of you have probably seen on occasion a tweeter or midrange is wired out of phase or reversed positive and negative. This is done on purpose when phasing gets too far out of whack to bring it back in line. On paper only, at 6db per octave, a driver goes 90 degrees out of phase, 12 db goes 180 degrees (which is when you reverse terminals), 18 db goes 270 degrees and 24 db come full around 360 degrees. In real practice most of the time, these numbers are not near accurate. So 6/6 slopes can get you close in phasing, but why did Joe Di'Apolitto use 18 db slopes in his mtm designs.... harder slopes often sound better, they roll off any bumps in a drivers frequency response and they give the same type (in reverse) phasing as 1st order slopes. I have seen a ton of discussion in this forum about why 1st order slopes, but it is a rare few that understand why and how the drivers combined with crossovers affect phase and even time alignment.
"With a active crossover, time/phase alignment becomes relatively easy."
Agreed, and as someone who has those, if their frequency selection allows any choice from 20-20k which mine do, then it's a simple matter for me to just think up a combination of frequency selection vs slopes to play around with various drivers and compare the results on the fly from the lp.
Does 1rst order have advantages? Sure. But they have disadvantages, too, like all the other slopes. I've experimented from 1rst to 5th order (LWR, Bttrwth) and can tell you easily that, for sound's sake, I would never start with a crossover design and try to pin it onto a pair of drivers. I'd have to start with the real-world drivers and come up with the right crossover. I'd certainly consider what the crossover might look like when choosing drivers, but that's only all the more reason to give the driver selection the most consideration from the start. But, 1rst order behavior advantages are not the only consideration to good overall design.
But, with active digital crossovers, there's no need to spend all that time reading all the tea leaves (white papers, testimonials, reams of MLSSA charts, searching for who could be the most unimpeachable source of info on it, etc) in an attempt to get a handle on comparing them all from afar and then try to divine which might be best. With digital actives, you just dial it up and listen for yourself...a whole lot easier and faster that way.
What I can tell from that is, yeah, 1rst order can be nice, but it's not the holy grail. The holy grail is a well orchestrated and executed speaker design overall...not just one or two aspects.
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.
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.
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.
"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.
A decent active crossover in knowledgeable hands will crush the performance of a top tier passive crossover.
Haha so much crushing that nobody is bothering doing it except for some cheap eight dollar headphones. Real life hello? Anyway, let's put it to rest. Hi end market doesn't care for your digital amp and digital dsp stuffs stuffing into a speaker with drivers bought from China OK. Have you never bought any high end stuffs before? Can't you tell the difference between a $7K amp and some cheap digital make in China amp?
I am not going to use any stinking digital with my high end drivers bought from Seas or ScanSpeak or Accuton. It's like taking Ms. Kate Upton to McDonalds OK !!!
What am I going to do with my $5K vinyl table? Ain't no stinking ADC will touch it lols.
How about my $7K McIntosh tube amps? Ain't none gonna fit into the back of the digital speakers. The heat alone will burn up your speakers.
So why don't we put all these digital nonsense stuffs to rest. Maybe there's a "Made in China" forum where you can go to make your case there :-)
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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.
For what it is worth: The genetic difference between chimpanzees and man is 1%. Any two random humans differ by less then 0.1% genetically. Message: Small differences matter. In my experience, time/phase coherent speakers reproduce for example the applause of the audience in a life-like manner. Depending on the recording technique, they reproduce a space better. Inches matter. The distance between your ears or time difference of the arrival of a sound is what allows to localize the origin of a sound. Say that’s 6 inches or ~ 16 cm. Some may have bigger heads. 1 cm doesn’t matter? Think again.
I think you need to work on your bias as it is unjustified. More and more of the high end speaker market will go digital/active cross-over as the limits of analog cross-overs are a hard brick wall that cannot be scaled. I suggest doing some reading into it, it will likely change your bias if you keep an open mind about it.
If your turntable is only $5K, almost entry by audiophile standards today, then a good DAC, not even one that expensive streaming 24/96 or 24/192 either Qoboz or Tidal is certainly going to touch it if you compare recording to recording. So much has changed in just the last 5 years.
I will emphasize again there is distortion in dynamic speakers that cannot be corrected with an analog cross-over. It just cannot be done. In the digital domain, there is even the ability to address resonances that again, you just cannot do in analog. I am actually working on a "DIY" 3-way right now, with Accuton mid-bass and midrange. I have not picked my tweeter yet. The level of driver integration and flatness of response after correction is just not possible with an analog cross-over.
andy2 OP689 posts10-30-2019 10:54p I am not going to use any stinking digital with my high end drivers bought from Seas or ScanSpeak or Accuton. It’s like taking Ms. Kate Upton to McDonalds OK !!!
What am I going to do with my $5K vinyl table? Ain’t no stinking ADC will touch it lols.
Why would I want to use the same design methods we have been using for 100 years when superior ones exist? Lead, follow or get out of the way :-)
andy2 OP690 posts10-30-2019 11:22pmReal life statistics: what is the percentage of speakers sold here on Audiogon that are digital? It can’t get more real than that.
nice Little Feat reference Geoff, didn’t know ya had it in ya
” but only time will tell IF he’s a legend from heaven, or sent here from hell” Speaking of time, since 1977 with more than a quarter million time and phase ( and other cool stuff, because you know its a SYSTEM ) loudspeakers sold :-)
You are right that alignment between speakers in a cabinet matters, but localization via timing is based on the arrival time difference between your two ears of the same sound, whatever that sound is, even one that is not coming from a time aligned speaker.
aschuh7 posts10-30-2019 11:31pm Inches matter.
The distance between your ears or time difference of the arrival of a
sound is what allows to localize the origin of a sound. Say that’s 6
inches or ~ 16 cm. Some may have bigger heads. 1 cm doesn’t matter? Think again.
Are great when done right, so long as you don’t drive them with something like this. 75 degrees at 8khz, and still 40 degrees at 1.5khz. Then you may as well flip a coin with regard of mid to tweeter phasing or how you distant mount them from each other. https://ibb.co/WzTLkkL
@geoffkait , @tomic601 , big *S*...one of my faves too. But we surely need more coherent heroes of late, and that's about as much as I'll go into That...
Re 'electric supercars': Lotus Evija...and let's watch what Formula E does for the breed. And most of today's cars owe a lot to superbikes and the racing of.... ;)
For once I'm enjoying this forum, since I'm on the verge of wading into these weeds with my DIY endeavour. Since IMHO I'm a long-standing skeptic of the 'perceived' vs. 'measured', analog vs.digital, this X vs. Z 'enhancement' to the audio experience, a 'lively discussion' of the subject at keyboard is appreciated by y'all. *S*
Please, carry on...and play nice, 'K? ;) Or I'll sic the Watchmen on y'all...*L*
(Oh, FYI...have a Behringer DCX2496 to play with. Yup, digital domain domination...)
I built a speaker. Accuton Diamond tweeter, Accuton 2" ceramic midrange, Acoustic Elegance TD6m midwoofer, Acoustic Elegance TD15H+ woofer.
I fine tuned a Linkwitz Riley 2nd order 4-way series crossover.
After the crossover was set, I tested and fine tuned driver depth (time alignment). This took more time than fine tuning the actual crossover.
At normal listening levels, the speakers are fabulous.
At concert hall levels, there was something that was ever so slightly off. After double checking everything, I conducted an experiment; tilt the tweeter/midrange/midwoofer section sideways (yes it looks funny). After a few test listens, viola!. I had set my tweeters 1mm too deep. Or, the foam on the back of the 2" ceramic midrange was thicker than the tweeter, so it didn't sink as deep. It's now perfect. Time alignment achieved.
My wife can't hear the difference. She thinks I'm an idiot.
I have OCD. After I took the online test, a brief explanation was given; people with OCD reorganize complex patterns in their head. I can 'sense' the improvement, my wife can't.
My conclusion: some people can sense phase issues, some people can't.
Andy, you have opinions that you don't understand. I'm happy to stick to your original premise, but slamming others for giving accurate information does not work. You never know, a couple of these guys could be speaker designers and worked with most of the quality parts that you have mentioned. If you want my help say so, I'll chime in. If you'd like to continue telling everyone how it is. I'm done, Tim
@cousinbillyl, While I can neither confirm nor deny your deduction regarding OCD and audio time sensitivity, I do believe that your onto something. I have come to the conclusion that though for the most part that we may all basically hear similarly, we listen differently. For what ever reasons we prioritize some things we listen to differently, whether consciously or not. This amongst many other things can include the degree of perception of time in audio.
Andy, you have opinions that you don't understand. I'm happy to stick to your original premise, but slamming others for giving accurate information does not work.
I am still waiting for someone to tell me who can understand time-phase coherent, including all the experts in the world )-:
:-(
"
I am still waiting for someone to tell me who can understand time-phase coherent, including all the experts in the world )-: :-(" That I can help with.... First understand "Time Alignment" The speed of sound moves at the same speed at all frequencies, so the first battle would be to make the sound of the tweeter, mid, woofer or any other driver to hit your ears at the same time. The most common way is to align the voice coils, where the sound of the speaker originates from. When coils are in alignment, the sound from all drivers hit the ear at the same time. Could be done by staggering or a slanted front etc. Next ... Phasing: One reason that a single driver does so many things right is that there are no phase issues. A single driver does not have to move in unison with any other drivers. So what is phasing? All drivers moving in perfect unison.... when one driver starts moving outward, all drivers move outward at the same time, when it comes back, all drivers move back at the same time. This helps tremendously to prevent smearing or to improve pinpoint imaging. So what did I mean when I said that cross overs change phasing... A single cap or 1st order crossover, normally will cause a phase shift of 90 degrees, so to keep the next driver moving in unison, it must also be moving 90 degrees out of phase to stay in unison with the other driver. Again, 24db per octave brings you back around 360 degrees to put drivers back in phase, but the crossover parts count, the sound of the crossover parts being used and the practice vs theory that you don't truly end of with absolute phase cause most to not use 24db per octave slopes. Time/Phase Coherence is just what it sounds: Time and phase working in conjunction to form a Unified Whole.
I hope that I have expressed this in a way for everyone of any level to understand, Tim
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