Sloped baffle

Maybe this is a subject for another discussion, but I was wondering if coaxial drivers (TAD, KEF, Tannoy) are more likely to be time and phase coherent?

TAD and Tannoy are not time coherent. The little KEF 50 with the coincident driver is not.

What does this mean to the listener? Without a listen, it means little. The TAD Reference represent some of the best speakers at any price. That little KEF is great. The Tannoy are some of the most loved speakers, and have had a very long life as a studio speaker, with uncountable numbers of musicians hearing themselves on them after playing. Would anyone postulate that these musicians don't know how they themselves sound?

Again, this would be a nice thing to have, as perfect radiation patterns, perfect frequency response, perfectly inert cabinets, zero harmonic distortion, zero intermodulation distortion, and zero driver resonances would be nice things to have. No speaker has it all, so the sonic result of the compromises chosen is the real key.

Again, listen. Do not fixate on any one or two features, that will lead you nowhere in your quest for a speaker that sounds most like real music to you.

06-24-14: Bifwynne
I'm hoping Al and Ralph weigh in here to help us better understand the relative significance of phase coherence as compared to other factors.

Hi Bruce,

As I indicated earlier, speaker technology is not one of my areas of expertise, and about all I can offer is my suggestion that some insight into that degree of significance can potentially be gained by attempting to correlate one's subjective reaction to a wide range of quality speakers with JA's step response plots for those speakers.

I'm hoping Al (Almarg) and Ralph (Atmasphere) get around to reading Roy's articles and sharing their comments.

I've read through the "Loudspeaker Phase Accuracy and Musical Timing" article. IMO it is a brilliant and informative article, which certainly inspires very high confidence in the designer. But my feeling, consistent with Kiddman's comments, is that in audio there are always multiple ways to achieve success.

Best regards,
-- Al

06-24-14: Kiddman
I would have to see the detailed measurements to accept the,

I agree with this as well. It's just too bad that there aren't many to view/study.

IMO, unlikely results claimed by this manufacturer.

I disagree with this statement (given my personal experience) but I would have written "unverified claims by this manuf". Owning & listening to those speakers leads me to believe that such type of specs are achieveable by this manuf.

Investing hours in driving to dealers, or flying, asking manufacturers to let you hear them, flying to audio shows, those are all much better ways to make an educated guess about how you will react to the sound in your home.

indeed, I have done most of the items in this list - I have not asked manuf to loan me speakers to listen in my home - but I've done all the other items.
I was at RMAF2013 & listened to 95% of the rooms in the Marriott Tech & walked over & listened to all the rooms in the Hyatt. I heard a lot of speakers - most speakers were in "bad" rooms (typical show environment) except for those speakers put into huge ballrooms & other conf rooms. Most of the speakers sounded very blah except a very few. And, one of them was the Green Mtn Audio room. I was there all 3 days & I listened to the Green Mtn Audio Eos speakers each day. After hearing so many blah sounding speakers, it was a relief to listen to the Green Mtn Audio Eos - they sounded like music, great dynamics & Roy was playing all kinds of music (not audiophile CDs - just regular redbook music). Those speakers sounded good on every genre. This excellent sonics caught the attention of Stereophile: http://www.stereophile.com/content/marigo-whirls-green-mountain

FWIW. IMHO. YMMV.

Pay attention to those manufacturers that have intentionally run the mid driver in reverse phase to the tweeter and woofer. This indicates a bandaid approach that will ALWAYS compromise timbre, the accuracy of which is dependent on time and phase coherence.

The best answer I've heard for using a sloped baffle came from Paul Hales,... "It looks cool"...

http://www.stereophile.com/floorloudspeakers/699hales/

It's not crystal clear to me that Hales really said that, from how it is written. It does not appear to be a quote.

But it would be so very refreshing to hear that honesty from a designer.

I believe it. Hales uses fourth order crossover. It is of course not time coincident as one can see from the step response. You could speculate that part of the intent is to visually differentiate the transcendence from the revelation line, which it does.

Reversing the polarity of a mid in a 3-way or a tweeter in a 2-way is just a result of correcting for the phase shift of the crossover. The exception being 4th order. It's about getting the drivers to sum correctly. If they were 180 degrees out of phase, they cancel around the crossover point. In fact, one of the best ways to confirm the drivers are in phase is measuring the reverse null.

Now, if you want to talk about absolute phase and the half a millisecond @ 2000 Hz between cycles and whether that's audible, that's a different story. I don't know the audibility threshold up there but down around 100 Hz, it's around 30 milliseconds and several cycles for our ears to respond. Less for the trailing edge.

http://www.audioholics.com/room-acoustics/human-hearing-phase-distortion-audibility-part-2

That's bound to be misunderstood. Related articles in links.

The 30 milliseconds I mentioned previously came from a U-tubed Earl Geddes seminar on multiple subwoofers in a small room.

Remember, all these are opinions of folks based on their perceptions, with most of them marketing something (though Geddes does not sell subs). You were not there for the experiments. It is all self-reporting. So time aligned, phase aligned, time and phase coherent, one sub, two subs, many subs....take it all for what it is: "Self-reported" opinions based on experiments where the experimenter was the only one observing.

You have to try the products yourself, or hear them in a good setup, to form your own conclusions. And still you won't know if it is the "main feature" the manufacturer is touting that is dominating the sound, or other details of the product.

Remember, we listen to music, not features.

Sometimes I feel that in audio, buyers and enthusiasts would rather talk features than simply sit and listen to see if it sounds like music.

I think that Kiddman makes good points here. There are so many interactions and variables in the design of loudspeakers that it's got to be very hard to isolate which factor results in a speaker that you ultimately love.

To wit: you couldn't have two more different small speakers than, say, GMA Chromas and Harbeth P3ESR's. "Leaky" plywood cabinet vs. synthetic stone cabinet. Metal dome tweet vs. cloth tweet. "Complex" crossover vs. "simple" 1st-order crossover. Inverted driver polarity (!) vs. not. "Radial" cone material vs. paper-composite. Flat face baffle vs. slanted baffle. And the list goes on and on.

Now, then, various audiophiles swear by one or the other of these speakers. But who can really say whether it's the cabinet material, driver material, crossover topology, phase/time coherence or (most likely) some combination of all of the above that gives the results that you get? And THEN, factor in the room and the associated equipment and the tastes and hearing of the listener and you have more variables than anyone can deal with.

So, yeah: I can see that you might become fixated on the theoretical merits of time coherence and then fall in love with a non-time-coherent speaker, anyway.

Reminds me of the joke about the unmarried scientist who feeds his theoretical preferences in women to a computer and then cross-references it to a database of women in his city. One day he approaches his lab assistant and says, "Well, it seems I have actually found the woman of my dreams. She meets every one of my requirements."
"Then why the glum face?" asks the assistant.
"I just don't like her," he sighs.

Ng... thanks for the phase coherence article. The article seems to be based on scientific controlled studies and tests. Rather than paraphrase the conclusions, I copied them here:

"So what conclusions regarding the audibility of phase distortion can we draw from the all of the above?

'Given the data provided by the above cited references we can conclude that phase distortion is indeed audible, though generally speaking, only very subtly so and only under certain specific test conditions and perception circumstances.

'The degree of subtly depends upon the nature of the test signal, the dB SPL level at which the signal is perceived, the acoustic environment in which the signal was recorded and/or played back as well as the Q & fo of any filter networks in the signal stream. Certain combinations of conditions can render it utterly inaudible.

'Room acoustics further masks whatever cues that the hearing process may depend upon to detect the presence of phase distortion."

And here's my personal bottom line. Phase coherence is just one of many variables that is taken into account when designing a speaker system ... and there are many. As many folks have said, trust your ears and audition as many speakers as you can. But ... if I was asked to buy speakers based on their phase coherence characteristics as a stand-alone factor, I personally would not.

Thanks again Ng.... Good article. It puts the issue into context.

Bruce

And here's my personal bottom line. Phase coherence is just one of many variables that is taken into account when designing a speaker system ... and there are many. As many folks have said, trust your ears and audition as many speakers as you can. But ... if I was asked to buy speakers based on their phase coherence characteristics as a stand-alone factor, I personally would not.

Bifwynne, I disagree here. Of course, you are entitled to think about this the way you choose, just as I am.
There's too much research - of the wrong type - that convinces people that time-coherence is one of the many issues/parameters to be resolved in speaker design.
After hearing time-coherent speakers vs. others, the speaker should be designed around time-coherence & issues re. that speaker's design should be solved in the context of time-coherence. When that speaker is correctly built as a time-coherent speaker it will simply be far more realistic, dynamic & accurate to the recorded music than any other speaker in its price range. From my experience, I'm convinced - there ain't no other way to go.....
Others who have also had such an experience feel the same way not surprisingly.
sorry to see that (once again) this crowd has missed the point re. time-coherence. :(
When you have a chance, listen to a time-coherent speaker (doesn't have to be Green Mtn Audio) & compare it a non-coherent speaker.....

Bif,

Don't get me wrong. Phase is taken into consideration on any competently designed speakers. My first didn't but I wasn't particularly competent then. Not yet either. Still, with four 6-1/2's per side, they sounded more dynamic than any "coherent" speakers I've heard short of the Dunlavy SCIVa. Never considered the two were related.

Time coherence implies that the first cycle of a tone is more important than the second or third. That, I'm unsure of. Really, I don't know. Low order crossovers have advantages, including transient behaviour. I like them because they're simpler and cheaper but not for all drivers and circumstances.

Here's the test... Listen to any 2.5 way speaker. By design, the woofers roll off at different frequencies and must have increasing phase separation as frequencies increase. 45 degrees by 1000 Hz is fairly typical. According to the article, where our ears are most likely to detect. The .5 woofer will be lower SPL but still audible. Can you hear any phase distortion?

Problem is that we don't hear distortion as distortion, not unless you have the trained hearing of a professional under controlled conditions. It can be measured by instruments but human brains interpret those as frequency differences and there could be any number of explanations including comb filtering, diffraction, or the driver. Almost as easily, they can be masked.

So, forget the test, it's useless. More likely that someone will misinterpret that as all 2.5's are ....

Ngjockey and Bombaywalla ... I find the issue of phase coherence to be intellectually interesting. I also find Roy's article and the article Ng... provided to be equally interesting. If I had the time, if there were more B&M stores around with a variety of speaker types, and if the salepeople were game to burn time to experiment, I'd love to build up a personal anecdotal portfolio of experiences.

To date I have only one data point, which is almost useless. I spent 90 mins about 2 years ago with Vandy Treos. They just didn't do it for me. Imagaging, soundstage and musicality were nonextant.

And if the pushback is that they weren't set up correctly, or wrong cabling, wrong positoning, not leveled, and so forth, my response is .... still not impressed. Even if the Treos would have taken me to the 8th dimension if all the foregoing variables were controlled ... I am still not convinced. I want to flip the switch and listen to music. Not interested in using an oscilliscope to figure out how to enjoy music.

This is a fascinating thread. I hope it will continue to attract more comments from folks who have relevant experiences.

BIF

I believe one of the members had posted that the tweeter is 180 degrees out-of-phase in a 2nd order system.
I believe that this is wrong info. If you read Roy Johnson's 1997 article in Audio Ideas Guide he says otherwise & I quote

Contrary to popular belief, the 180-degree shift doesn't mean that the tweeter is out of phase with the woofer. It merely leads the woofer output by 180-degrees, or half of the wavelength of the crossover frequency....
Figure 5b also shows that the amplitude response (derived from steady-state tones) will have an infinite 'suck-out' Tw + W. At first glance, this cancellation does, indeed, seem exactly like that caused by a tweeter with reversed polarity. What is really true is that the time delay is causing cancellation on steady tones, because the time delay at the crossover frequency is half of a wave cycle, 1/(2f) seconds.
To 'fix' the problems of the system, a designer will often reverse the tweeter's wires to invert its polarity. Although the steady-state results shown in Figure 6a look much smoother, in reality this is because the graph for the tweeter's phase has had 180 degrees subtracted.

This seemingly minor point forms the basis for the many claims of 'phase-coherent' performance, which, at best, is a half-truth. The graph now shows 'a smooth rate of phase-angle change at the crossover point.' But it isn't smooth from the perspective of time passing by. In fact, regardless of how smooth this curve appears, the woofer and tweeter still have the same sequence of arrival as before.

Reversing the tweeter polarity only means that the tweeter is moving inward on the initial pulse while the woofer moves outward. This is evident in the square wave response in Figure 6b: The tweeter is pulling in while the woofer is pushing out. At the highest frequencies, the tweeter still arrives as before (in Figure 5), and now its absolute polarity will still be backwards.

I think that Al already provided us a link to this 1997 article so I will not repeat it here.

I want to flip the switch and listen to music. Not interested in using an oscilliscope to figure out how to enjoy music.

precisely! Even more reason to own a time-coherent speaker. Time-coherent speakers, when compared to non-time-coherent speakers, when properly designed, will be more dynamic, more true to the recorded music & simply more realistic. That's the kind of speaker to have in one's room if you want to simply "flip the switch and listen to music". With time-coherent speakers you will leave the oscilloscope on the test rack (where it belongs) & you listen to music.

Problem is that we don't hear distortion as distortion, not unless you have the trained hearing of a professional under controlled conditions. It can be measured by instruments but human brains interpret those as frequency differences and there could be any number of explanations including comb filtering, diffraction, or the driver. Almost as easily, they can be masked.

So, forget the test, it's useless.

I think that this is a bad attitude to have. Basically this says, "you are not trained to listen & you are not getting it, so drop this issue & don't make the effort to learn. keep the status quo".
I say that if one wants to become a better audiophile, a better listener, a better consumer, one should challenge oneself to reach higher & try to understand things that are at this time outside one's grasp. One should challenge one's norm or the norm & you might find out that there is indeed a better way to do things & this enlightenment might bring more satisfaction & joy in listening to music.

if you surf the Green Mtn Audio website, there are article on how to listen. http://greenmountainaudio.com/how-to-listen-to-music/

http://greenmountainaudio.com/how-to-choose-speakers/

One needs to understand that if a speaker is not time-coherent, no other parameter will make up for this. When it comes to time-coherence, you cannot juggle it/trade it off w/ other design parameters - you either have time-coherence or you don't.
Time coherence is not a 'fascinating' concept or idea. It's real & properly implemented makes the difference between enjoying music & listening to top quality sound.....

Bomb,

That was not my intended meaning. Simply put, we're human.
Obviously you have your opinion and I'm not trying to argue, passive aggresively or otherwise. I may have reacted a bit sarcastic when I thought you overstated.

Perhaps you can explain something to me. In GMA's specs, they state phase shift acoustically over given frequencies. Does that mean impedance phase (reactance) or total phase? Either way, impressive.

Hi Ngjockey,
OK, thanks for the clarification. :-)

In GMA's specs, they state phase shift acoustically over given frequencies. Does that mean impedance phase (reactance) or total phase? Either way, impressive.

this is really a question for Roy Johnson (who designs these speakers) but from my many detailed chats with him & from my ownership of his speakers, I believe that he is citing total phase shift - it's acoustical & electrical combined. The driver selection is critical to achieve this kind of minimal phase response.
If you read that same Audio Ideas Guide article he clearly states that driver selection is key & I quote

.....What he means is that the drivers must be well-behaved far beyond their crossover points to be used with a first-order circuit, because this circuit allows the drivers to overlap across a wide range. To be used with a first-order crossover, only the best drivers need apply.

The "he" in the above quote is referring to Siegfried Linkwitz, just FYI.

Roy J: you might want to chime in to clarify your speaker spec. Thanks.

I have a little experience with owning Thiel 1.2's. I think they were suppose to be phase and time coherent. At home I have never heard a speaker do most things as well as them. It seemed to me the musical cloth was all from one piece. No discontinuities. I could follow the scale up and down the piano without a noticeable bulge or reticence on a certain frequency, and not imagine it was real, because it sounded as real as it could get as a recording, even though that speaker was not state of the art even in Thiel's lineup. That allowed me to enjoy the flow and nuances of the musical presentation better than anything I have ever had. Some speakers convey an instrument truer in some senses than my Theils to me, and some have conveyed the recording venue better, or spacing of images, macro dynamics, and other attributes better, but not the whole musical package. To me the Thiel's presented a realistic presentation of the whole. It was to me, like everything presented fit. It doesn't seem to do it justice to break it down in descriptive terms but it seemed relatively speaking it didn't get more real the that.
So I have always been curious to hear the sound of Green Mtn spkrs. Maybe someday. I have heard Vandersten 2ce's, so while I didn't care for the warmness of the spkr I did notice a whole cloth sound that was easy to see the whole picture of the musical presentation.

^+1:-)!!!!!
That's exactly how I've feel.

Hi all,

Sorry to have delayed this post-- unexpected duties arose.

I hope the majority will be served by some words below, along with a close study of the diagram I've posted at

http://s1374.photobucket.com/user/greenmountainaudio/media/TimeCoherenceDiagram_zpse8c92f2a.jpg.html?filters[user]=140737398&filters[recent]=1&sort=1&o=0

For whatever reason, I cannot get this to post as a clickable link here, sorry. Perhaps someone else can! At least Cut and Paste works, so please open this image in a new window/tab and magnify, as it illustrates much of what takes too many words to explain.

Here we go:
When a speaker spits out a brief piece of sound, making just a "Beep" then falling silent, what is moving towards us is a chunk of higherthenlower ("wavering") air pressure. The air itself is not going anywhere.

I encourage you to conceive of this as a traveling packet of sound, silent before and silent after, a packet that contains perhaps six wavelengths (six cycles) of a pure tone just like what is emitted from a tuning fork.

However, that one "Beep", high or low ("Boop"), is not a perfectly accurate example for a 'pure tone'. We must imagine instead that "Beep" stripped of its B and p, leaving only the eee or ooo.

That simple burst of an 'eee' or 'ooo' still conveys useful information- perhaps to warn of a car door ajar. Its message comes from its possession of just two characteristics:

1) It has a unique tone, high or low on the scale,
2) Lasting for a unique period of time.

Thus, to make and then hear any message takes both tone and time. Time is important to our sense of hearing.

Non-time-coherent speakers delay bass tones more than voice range tones, and those tones more than its highs. Another way to state this is their highs always come out first/too soon. This cannot be completely fixed by digital delays nor by stepping the tweeter back from the plane of the mid, because the amount of time delay is DIFFERENT at EACH frequency, which also leads to serious measurement difficulties for most designers.

Perfectly time-coherent speakers do not delay ANY tones whether bass, voice or treble.

Designers of non-time coherent speakers quote studies showing we cannot hear less than a 2 millisecond difference in arrival between the voice range and the high treble.

This means they believe it is OK for the mid's voice range to arrive up to ~60cm (two feet!) after the tweeter's highest tones. And even greater offsets/longer-delays are OK in the bass.

When those tests first came out, I saw they misled by only using tones that do not mimic the complex sounds of music, nor even resemble sounds anyone has grown up experiencing everyday naturally, so untrained listeners instinctively would know how 'it' is supposed to sound.

For myself, after years of being intimately near to the artistry of very many world-class musicians and singers, each for long hours, sometimes for days on end (rehearsals), I think "Who are engineers to say time delays are OK-- that somehow those don't screw up the music?"

I have no doubt everyone has watched even simple music bounce along on the computer screen. Know that we are observing only a miniscule faction of that music's waveform.

When a loudspeaker injects time delay, the shape of that waveform changes. The 'wave envelope' changes.

What is in that one shape, inside that one envelope? A zillion different sounds, each occurring with its own unique loudness, tonality, onset, duration, and decay. In that shape also lies the ebb and flow, the give and take, the emotion of the music, and the texture of each sound, its unique timbre ('tam-burr').

And we only get to see and record that one complex wave-shape per channel. So I think best to strive not to change it and hear what happens.

When this time-delay-as-we-go-lower is progressively removed from a speaker's design, along with the sonic reflections off its cabinet surfaces, then we always hear from any recording more and more the sound of people playing music 'over there'. There are no microphones. Our attention is no longer drawn to "the details" such as "the sound of the bass", "the airiness of the highs" or the sharpness of images.

Instead, even an inexperienced listener soon focuses instead on HOW the bass player is responding to the others (and thus WHY). All of the hi-fi 'details' are still there but now serve to shape the tones, to give each sound precision and purity (or perhaps a wandering pace and a fuzzy tone) RELATIVE to all the other musicians' sounds. Also, each musician remains distinctly separate in space, regardless of the music's complexity.

Ebb and flow, sudden changes- all are part of music, and hearing those makes sense to the ear. A much wider range of music is enjoyed, with little effort. Music FEELS good, just as if you were a teenager again, before becoming caught up in hearing all the very cool and entertaining 'hi-fi details'. You also do not need to turn it up.

By the way, speaker designs have become far more time-incoherent since the 1970's. Marketing pressures combined with the appeal to designers of 'new technology' has led to the use of many drivers that require high-order crossovers to operate.

This has given the majority of audiophiles, reviewers and designers loudspeakers that present "details" instead of music ("I can't stand loud rock recordings from these expensive speakers!"). They do not hear this as being a problem due to time-delays for any or all of several reasons:

a) They have not gone to enough intimate concerts, live theater or recitals, or sat in a living room for hours listening to singing or an acoustic guitar, clarinet, piano, a violin, played superbly. In that intimate environment, such sounds are to die for; far more breathtaking that us mere mortals can imagine- until we hear 'it'.

b) They play only a limited variety of recordings to evaluate gear, much of those recordings electronically manipulated, even of acoustic instruments (I read the reviews).

c) They have collected some non-musical gear and cables, as there is a lot of it out there, some very expensive. Very clean, but sterile, devoid of musical flow.

d) They have been told over and over again that time-coherence does not matter. No editor wants to piss off any large speaker manufacturer that uses only high-order crossovers.

e) They have lived with only very time-incoherent speakers, never with original Quads, nor electrostatic or planar headphones.

f) They do not know how to work the math of speaker design from a time domain perspective, and I don't like it either.

g) They have ears of cloth, for which no amount of exposure to live music can help. Fortunately, I "had to take piano lessons" as a youth, enjoying it and eventually playing much music well enough as an adult, from Mozart to Bartok to Joplin, to know how terribly bad I still was compared to any prodigy! Now I am long out of practice, as the piano needs new strings and new action ($$$)-- an Everett upright grand from 1887, weighing 600 pounds with a bronze frame holding a spruce sounding board. Sorry to digress.


So, we have that "eee" from the speaker coming towards us at 343 meters per second, no matter whether it's a bass tone or a treble tone. It will arrive at our chair in about 10 milliseconds, to begin to push or pull on our eardrums, because we are sitting about 3 meters away. Unless the speaker delayed when this sound came out.

A jet liner up high is cruising at ~85% of this speed. Sound is about ten times faster than cars on a distant highway. It is the speed of that blast of pressure coming at us from an atomic bomb. We could see ordinary sound traveling if the air weren't so clear.

Non-time-coherent speakers create time delays by their choice of drivers, those drivers' locations from your ear, and the type of crossover circuits used.

Drivers have both mechanical time delays and electrical delays, as they are Transducers, which operate in both domains.

A tweeter may be stepped back from the mid, to "put it perfectly in phase with the mid" at the crossover point only. This still does not make for time-coherent operation (study my diagram and my other Audiogon posts in the links others supplied above, thank you).

ALL crossover circuits introduce time delays, but only first-order crossover circuits create time delays that naturally offset each other, when crossing from the tweeter to the mid, and mid to woofer, thus producing no RELATIVE time delay between the drivers, which is the (my) goal.

I hope this helps! For those wondering what the step response or the impulse response indicate in Stereophile, I advise you to study John Atkinson's explanations of them and to remember that, in those tests, nothing nearly as low 'C' above middle 'C' is shown. That takes a large, expensive anechoic chamber or careful measurement outdoors with the speaker up on a pole, far away from the ground, using a very loud pulse, one that likely damages any tweeter.

The detractors of first-order speakers talk of power-handling issues caused by the slow rolloff of the crossover allowing bass to get into a driver, even a tweeter, making it distort or melt. Maybe the mid's cone would ring in the tweeter's range, because of its strong resonance at a high frequency. For us, there has been no problem because we use the best drivers, by anyone's standards.

Detractors also claim there will be off-axis cancellations between drivers, leading to a weird tone balance for a listener off-axis. Not true with proper crossover points, slender cabinets, and a lack of cabinet reflections. Never is the math behind those claims shown, as it never supports them.

To the original poster- thank you for this opportunity, and know that one reason a tweeter is placed behind the plane of a mid is because the sound from that mid emerges first from down deep in the center of its cone, no matter the crossover slopes used nor the mid driver's design.

Best regards,
Roy Johnson
Designer
Green Mountain Audio

Thank you!

Thanks for chiming in Roy. :-) Thanks for the explanation in your long post.

Remember, that long post is essentially a non-scientific, non-specific, biased piece of salesmanship by a guy who builds products that allegedly conform to this behavior.

I have no horse in the race. But I do like some speakers in each camp...those that conform (proven by measurements) and those that don't. I have to submit that time coherence is not the driving factor in speaker sound.

Put another way: an absolutely horrible, highly distorted speaker that is time coherent could easily be made, and great ones that are not are also made.

Again: listen with your own ears.

Kiddman, no one benefits from your insults.

If you did the math, or at least read my technical papers and relevant papers in the AES Journals, and above all hear what everyone we know hears, you would agree with me, no doubt.

You could read my letter to six moons describing the problems that measuring speakers presents, and WHY each measurement technique has particular problems. No Roy opinions there-- just scientifically-tested facts accepted by the AES.

The complete sets of measurements we post on our website for our speakers are far more detailed than any others anywhere out there.

You are wrong about being able to make a highly-distorted speaker somehow time-coherent. Its drivers themselves would not even be minimum-phase to begin with (that is, well-behaved) to be able to employ the required first-order crossover.

Best regards,
Roy

07-04-14: Kiddman
........I have to submit that time coherence is not the driving factor in speaker sound.

Put another way: an absolutely horrible, highly distorted speaker that is time coherent could easily be made,.....

Kiddman, I'm afraid you are quite clueless & remain so. you really have no idea, do you? The more you write, the more ignorance you show in this matter...

You may feel insulted....but that does not mean I'm intending to insult you.

I can reprint papers on mixture flow in internal combuston engines, but that does not mean the heads I flow are perfect. It only means I can write theory. Self-published graphs and dyno runs done by me don't prove that they were the runs for that motor, and that the science I can read, then write papers about, ensured that my engine is the best.

I would love for your speakers to be the best, that would represent an improvement. Which upcoming show will you be playing them at? Which top electronics manufacturers are using them? Surely they must be making a splash in the industry if they are that great. I simply can't wait to hear them. Tell me where.

Kiddman

Bombaywalla, you've never designed anything, have you, or you would know what I said is true. A very poor speaker can be made that is still time coherent, and if you can't get that far in your brain you have little experience and education.

I have no doubt Roy is sincere and his efforts are genuine. I don't have enough information to intelligently debate his views either way. Beep is an interesting phenomena in itself.

I don't doubt his sincerity and efforts either. Some great products are made by such sincere guys making large efforts. And many more lousy ones are.

I'm going to seek them out for a listen.

Wasn't Jon Dalqhuist's DQ-10 an early attempt at time coherence? And, ditto, Wilson's Franken-speaker, the Whamm?
It's been so long since I heard either speaker I couldn't say how either stands up today. My concern, in theory, would be that multiple drivers, with a bunch of different crossovers, adds more complications to the affair. But, I guess, as they say, in practice, theory and practice aren't the same.

For a ubitiquous speaker that shows good time alignment, look no further than Vandersteen Model 2. A fair speaker for the price, but a hooded, somewhat grainy sound in the mids and highs with bass that sounds like a cardboard box. So time alignment it has. OK sound for the price. But nothing more than OK. If time alignment were so important, how can this speaker sound so ordinary, so mediocre?

Because extension matters, driver resonance matters, driver distortion matters, driver symmetry of motion matters, overall harmonic distortion matters, intermodulation distortion matters, box colorations matter......and we can go on and on.

So there you have a great example: a manufacturer that makes a barely passable (to my standards) time coherent speaker that I would never own, and he makes a fantastic, state of the art speaker that I would be happy to own. Any more demonstration needed that time coherence is not the most driving factor in the sound?

Kiddman,

You are absolutely right. Solving one issue (If at all, in this case) , while creating many others is a far cry from good engineering, or good sounding loudspeakers. People who get stuck behind “critical” issues, usually do not see the entire forest. Move on, you are wasting good ink.

07-05-14: Kiddman
For a ubitiquous speaker that shows good time alignment, look no further than Vandersteen Model 2............
So there you have a great example: a manufacturer that makes a barely passable (to my standards) time coherent speaker........

Kiddman, you are screwing up again!!
In your 1st sentence you wrote that the Vandy Model 2 has TIME ALIGNMENT.
In a sentence much you lament by saying that the Vandy Model 2 is TIME COHERENT (which is wrong) & how could it be so bad sounding.
The Vandy Model 2 is time-aligned & that's it. The Vandy Model 2 (therefore) is NOT time-coherent.
Time aligned speakers are NOT necessarily time-coherent.
The other way is true - time-coherent speakers are time-aligned.

Ever since you participated in this thread, you have been NOTHING but negative - casting doubt on this subject matter & being insulting - and, yet, you have contributed NOTHING & no information to this thread/subject matter. By reading your posts, other Audiogon members gain no new information except determine that you are a stubborn 'nay-sayer' with perhaps little experience. If you have no positive contribution to make, go find another place to spend your time rather than driving off the other members who come here to learn something new & different. Your negativism benefits nobody....
And, don't cast doubt on my experience & education, you jerk!

Bombaywalla, please list the major speaker brands that are time and phase coherent. At this point, I am aware of three brands: Vandersteen, Thiel and GMA. Are there others?

The reason I ask is because I'd like to check area dealers who sell time and phase coherent models and maybe do some comparative auditioning. The other alternative is audio shows.

Thanks

Bifwynne, yes, I think you have the list.
Single-driver speakers are also time coherent (since they dont have a x-over to begin with) but they might not have the freq range extension you are looking for.

Some of the latest generation Martin-Logans might also be time-coherent (they claim to have made big strides in integrating their woofer with their ESL panel) & the full-range CLX.

Quad speakers are also time-coherent such as the ESL-2085 & they might other models (ESL-989?)

Another brand is Eminent Technology LFT 8. They might have a latter rev of this model, not sure.

Yet another brand would be Sanders Sound Systems 10C & 11 ESLs. You'll find measurements of the Innersound Kaya & Eros Mk3 speakers on Stereophile if you search. Innersound speakers were basically made by the same person who owns Sanders Sound Systems today. I realize that I'm extrapolating since Innersound Kayas were time-coherent that Sanders Sound Systems 10C/11 will also be. This is based on a reasonable assumption that the same designer has not changed his philosophy when he started his new company. Atleast I did not get this impression when I spoke to him in Dec 2013/Jan 2014.

I'm almost willing to say that SoundLab ESLs are also time-coherent but I might be wrong here. Not sure.

That's all I can think of right now. If I think of more brands/models I shall post. Thanks.

Bombaywanker, the Vandersteen 2 are time and phase conherent.

And that surely does not make it a state of the art speaker, like it makes no speaker state of the art.

Yes, I do doubt your experience and you sure sound like a guy with no technical education and little technical aptitude. Anyone who is fixated on one aspect of design and thinks it guarantees something is usually one who has little technical experience or knowledge. Someone who has experience and physics and engineering in his background always knows designs never hinge on one parameter or feature.

Usermanual and some others have it right, they recognize that this thread is only talking about one aspect of speaker design.

Just saw this thread. Wonderful to have so many knowledgeable folks chime in, plus the links to very good past discussions.

I'm certainly not up to par with my two cents here, but Psag might find it useful. Uli Brueggemann, the man behind Acourate DSP/DRC software, wrote this article on crossovers you are likely to find enlightening. It is in layman's terms: http://files.computeraudiophile.com/2013/1202/XOWhitePaper.pdf

Not sure what your system configuration is. Mine is based 100% on a computer server as source, which allows a neat approach - in my view, of course:

One way to achieve time and phase alignment is to use a multi-amped system (someone already said this above), having one amp directly driving a driver (no passive crossover used), and having a multichannel DAC and DSP software such as Acourate. Acourate allows to set digital crossovers and set time delays. So you can achieve time alignment without a sloped baffle.
Here's a great setup article http://www.computeraudiophile.com/content/556-advanced-acourate-digital-xo-time-alignment-driver-linearization-walkthrough/

I'm starting to go down this route, although I'm still coming to terms with the notion of the benefits of a time and phase aligned system where the amps are driven directly by a DAC (with the drawbacks of the latter) outdoing the benefits of my Lamm preamp driving the amp.

BTW, would like to ask a side question taking the advantage of so many knowledgeable guys reading this thread: following the above, my thoughts are of eventually replacing my speakers with DIY speakers using premium drivers, without passive XO, and enclosed in a DIY cabinet (I'm rather skilled at that). It seems premium driver (top Raal, Accuton, scanspeak, etc) can be had for relative low prices (compared to speakers that carry them). Does this sound like a good plan, or am I missing a significant issue??

Great thread!

Lewinskih01, your plan is great. There is so much info about making speakers in real texts, you will be surprised that it is not magic. First thing, yes, use the best drivers you can. Check out Audio Technology, they are some of the absolute best.

And sure, the prices are low compared to finished speakers.

Cabinets are time consuming, finishing is time consuming, this labor has to be accounted for to the tune of $100 per hour or so, all parts have to have markups, there is dealer markup. Without any gouging, prices escalate quickly.

You will learn so much in a diy endeavor, and you will end up with a good set of speakers if you research and execute well.

Start reading the DIY forum. You will find a number of folks who really know what they are talking about. Fewer "know it alls", But lots of guys who really do things.

07-05-14: Kiddman
Yes, I do doubt your experience and you sure sound like a guy with no technical education and little technical aptitude. Anyone who is fixated on one aspect of design and thinks it guarantees something is usually one who has little technical experience or knowledge. Someone who has experience and physics and engineering in his background always knows designs never hinge on one parameter or feature.

listen, Kidboy, if you think that I have no technical education or background then you are deeply negative in that area! I had a good laugh when I read the above...
the more you write, the more you put your foot into your mouth. At this point you've swallowed your 1st foot & your 2nd foot is well on its way down. Like I wrote before, you are totally clueless on this subject matter.
Time-coherence is not a "parameter or feature" of speaker design; it's a speaker design philiosophy. The designer 1st decides if his/her speaker is going to be time-coherent or not. Based on this decision, he/she selects drivers, x-over topology & then determines to solve all the other issues in designing that speaker under the umbrella of time-coherence.
You are far from getting that this concept. I suggest that you change your moniker to 'more_than_clueless' (BTW, you are the one who started insulting various Audiogon members & I'm just returning the favour as I wont sit back & take your sh$$. you are a most unsavoury fellow who doesn't know how to debate a topic without insulting people. That's why I wrote - if you are going to uncivil, go find another place to waste your time. Other Audiogon members do have disagreements but we all try our best to remain civil).

the Vandersteen 2 are time and phase conherent.

And that surely does not make it a state of the art speaker, like it makes no speaker state of the art.

And, look at your depth of knowledge on display here to the rest of the A'gon community! Your writings repeatedly say that just because the Vandersteen 2 model sounds bad that selecting time-cohrerent as a design "parameter" will not make any speaker sound its best. Wow! diffident mentality here. The Vandy 2 is a really old model speaker & it's very possible that Vandersteen was limited by the driver technology available back then. It's only recently that he started drivers made to his spec - maybe he realized the limitations of what was available to him commercially? I know that a lot of the manuf who make very good drivers have stopped selling them to the public. I had a friend who owned a pair of Vandy 2 which I heard for a short period of time & long ago & not enough to make a judgement on their sound.
Once again, time-coherence is design philosophy & not a design parameter. have you heard any other time-coherent speaker? Or, are you basing all this on the Vandy 2 speaker?

Time coherent speakers are not easy to make esp. with cone drivers that's why you have very few manuf in this arena. Your pee-wee brain has informed you that it's because time-coherent speakers don't sound good so manuf have dropped the idea. Wow! Perhaps it could be these speaker manuf incompetence in understanding time-coherence & translating that to a product that can be sold that has prevented them from manuf a time-coherence speaker?? Nah, that possibly cannot be the case, right??

Lewinskih01,
it appears that you are going down the path of (Boothroyd-Stuart) Meridian (the UK-based company). If you were able to stuff your amps into your speaker, you'd have an active loudspeaker like Meridian's along with your DSP x-over. OK, so now your are not listening to passive x-over components; you are now listening to the sound of your DSP software which is processing your music signal & creating delays to align the sonics at your ear/destination.
when it comes to using a DSP x-over another company called Emerald Physics is also using this concept. I've listening to their CS2 & CS3 speakers quite a bit - both at shows & at a dealer's place. Somehow I never took to their sonics. It also did not help that a new revision of the DSP x-over arrived every week or every couple of weeks with the pledge that it was an improvement over the prev rev.
IMO, with DSP x-over you sonics will be heavily influenced by the software (very much akin to having an oversampled/upsampled DAC - here again, the quality of the sonics is heavily dependent on the upsampling/oversampling algorithm. You already know for yourself that there are some oversampling/upsampling DACs you like & others you do not).
I personally think that it's much easier to overcome the sonic short-comings of passive x-over components than it is of the DSP software.
At any rate this post was to cite the trade-offs (which I'm sure you already know).
I applaud your effort, which is a big one - biamping or triamping & getting all delays & phase of the music signal correctly lined up. I sincerely wish you all the best. Do keep us Audiogon members posted on your progress.

It seems premium driver (top Raal, Accuton, scanspeak, etc) can be had for relative low prices (compared to speakers that carry them).

what is your definition of "premium drivers"? Cost of the driver? Cost of a commercial speaker using this driver? The marketing hype surrounding that driver that makes you believe it must be the best?
From the little I know, some Scanspeak drivers are very good performance that would qualify for time-coherence.
Accuton drivers need not apply for time-coherence.
I don't know much about Raal.
Be careful how you choose your drivers - don't let cost be the judge - look at their freq bandwidth & where you intend to cross them over. FWIW.

Proving that even those who totally believe in time and phase correct speakers can love a non-coherent speaker, read the following.

The Tannoys are not time and phase coherent. The higher order crossover prevents phase coherency, and that they are not time correct shows in every review where there is an impulse test, such as the review that these comments by John Atkinson were in:

"In the time domain, the Tannoy's impulse response (fig.6) looks typical of a design that uses a high-order crossover. Indeed, the step response (fig.7) confirms my suspicion from the impulse response that the Churchill is not time-coherent, despite its use of a coaxial drive-unit that places the tweeter diaphragm close to the acoustic center of the woofer. The tweeter output arrives at the measuring microphone first, followed by the woofer output."

Note that guy who argues heavily for time and phase correctness, Lewinskih, previously wrote, on this forum:

" the Tannoy studio monitors sound simply superb. They sound cohesive like the sound is cut from a single piece of cloth. The concentric horn-loaded tweeter is superbly integrated with regular cone woofer. The sound is very real. I've paired it with a tube amp & this combination seems to be a winner to my ears. The dispersion pattern of the speaker is 90 degrees the way the woofer is made & because of the horn loaded tweeter. Hence these speaker care much less whether they are mounted high up or sitting on the floor. I've actually tested this when they sat on the floor - the images were all up at my seated ear level!
I've tried these speakers with my s.s amp as well & they sound very good there as well. Realistic sound, excellent imaging, extended highs"

Since he waxes poetic about a design that has never time nor phase alignment / coherency, one can only conclude that these characteristics are not the "be all, end all" that many espouse.

I'm a fan of time-and-phase coherent speakers (and a GMA owner). Just want to throw that out there...

One correction to the conversation - single-driver speakers are NOT time-and-phase coherent. They would be if the speaker operates as a perfect-piston over the entire frequency range, but this is not reality. At certain frequencies, the driver can't respond as quickly as a perfect-piston, and the phase starts to lag.

Lewinski... great post. I was impressed by the various digital analyses and corrections that the software was able to effect. Hopefully, speaker manufacturers will be able to achieve greater time and phase alignment, driver linearity and low distortion by designing better X-overs. It may be that the best solution will be an active crossover that can effect the various functionalities that were the subject of your post.

I realize that Richard Vandersteen does this on his high end speakers to some degree, but it sure would be nice if it would be more plug and play. After all, not everybody is a former NASA rocket scientist or a Steven Jobs/Bill Gates computer genius.

Thanks.

The DIY forums and this one have something in common. Very rarely does anybody listen to any advice or criticism that they don't want to hear.

Lewinski... great post. I was impressed by the various digital analyses and corrections that the software was able to effect. Hopefully, speaker manufacturers will be able to achieve greater time and phase alignment, driver linearity and low distortion by designing better X-overs. It may be that the best solution will be an active crossover that can effect the various functionalities that were the subject of your post.
...
After all, not everybody is a former NASA rocket scientist or a Steven Jobs/Bill Gates computer genius.

Thanks Bifwynne.

Not sure if you were implying I'm a computer genius. But to clarify it just in case: I'm certainly not!!! Not even very savvy, honestly! It looks a lot harder than what it is. I just have a dedicated server with JRiver and the Audiophile Optimizer running in it. The hardware is optimized. Amazing sound. And it was a set it and forget it setup.

Cheers!

what is your definition of "premium drivers"? Cost of the driver? Cost of a commercial speaker using this driver? The marketing hype surrounding that driver that makes you believe it must be the best?
From the little I know, some Scanspeak drivers are very good performance that would qualify for time-coherence.
Accuton drivers need not apply for time-coherence.
I don't know much about Raal.
Be careful how you choose your drivers - don't let cost be the judge - look at their freq bandwidth & where you intend to cross them over.

Bombaywalla,

Very fair point. Honestly, I have not done much research on drivers yet. I was trying to provide examples to show what I meant and used the brands that are usually mentioned in reviews as premium. I did look into their prices, and in a way I was think along the lines of price. What would be premium brands sound-wise?

BTW, I never thought about drivers not being time-coherent. What does that mean? I thought time misalignment was between/among drivers.

I have not even started looking into building a speaker. I am now thinking through / coming to terms with moving away from a nice digital and analog chain (Audiophilleo with PurePower going into a Metrum Octave, going into a Lamm LL2) and into a multichannel DAC driving multiple amps directly and using software for volume control. I'm sure many can relate to having second, third, and forth thoughts on such a move.

The benefit of driver time and phase alignment seems to be significant. The benefit of multiamping I believe is well documented, but the challenge is on the implementation. Digital room correction also makes sense to me.

After taking this plunge next step will be thinking which amps to get to drive my existing speakers. And later I will look into building my DIY speakers. Nevertheless I wanted to chime in here to provide a different approach for achieving time alignment.

BTW, yes, in a way this is similar to the Meridian path. But I do like tubes!!! So my idea is a SS or class D amp for woofers and tubes for midrange and tweeters. And I also have two power subs. But you made me remember about Meridian's approach. I will look into it. I believe they deliver a digital signal to the speaker and then convert it to analog inside the amp. I'll check if they have processors that deliver multiple analog channels, but I'm also wary of spending big on digital components considering it is not yet mature and hence evolving so fast.

As I said before, great thread!

BTW, I never thought about drivers not being time-coherent. What does that mean? I thought time misalignment was between/among drivers.

Let's look at just 2 of the physical components of a driver (imagine a midrange driver): the cone and the suspension (the surround and the spider).

The cone itself has mass, and because of the kinetic energy of a cone moving outward, it sometimes just can't reverse direction as quickly as the signal is asking. Sure it responds, but with a very slight delay. This delay is one source of phase distortion.

The suspension not only centers the coil in the gap, but defines the resting position of the coil within the gap. Don't believe me? Gently push in on a mid-woofer, and let go. The speaker pushes back out to the resting position as defined by the suspension.

Now, small movements around the "resting point" all experience the same (minute) amount of resistance from the suspension. This is by design and is where the driver operates with minimal effective phase distortion.

Now, midrange drivers require larger strokes to produce lower frequencies, and the suspension applies more (nonlinear) resistance against the movement of the driver as the driver approaches X-max, imparting another set of phase distortions.

This is an oversimplification of the subject. But shows that (good) time-and-phase aligned speakers require more than just a sloped baffle and first-order crossovers.