green mountain.

[RoyJ]

Headphone Listening

At minimum this might be a good way to illustrate the significance of temporal cohesion?

Switching from my non-coherent speakers to headphones: where should I focus my attention to really hear the difference?

Good question, Jerry. One would focus on the sounds of various instruments and voices, using all sorts of recordings and a really wide variety of music (even music you don't like). It helps enormously to already know intimately the natural, un-mic'd sound of acoustic guitar and clarinet, singers, sax, piano, drums, Hammond B-3, you name it. All are important, since each occupies a unique tone range with its own dynamic and harmonic structures.

Clarity of details and textures (timbres) and all sorts of dynamic subtleties should become apparent, especially on complex sounds whose harmonic structures overlap the crossover points of the speakers in question. The difficulty for most people is these differences at first are almost overwhelmed by the difference between speaker imaging and headphone imaging, which is why it takes a long time using a wide variety of tunes, and why it helps to already know natural sounds.

I would start with what you most likely know the natural sound of, such as an acoustic guitar or the human voice, taken from many, many different recordings. It helps to know what a studio does to the microphone's signal, and the sound of different mics and what a mic hears when jammed right up against an instrument or a singer's mouth, sorry!

Best regards,
Roy Johnson
Designer
Green Mountain Audio

 

[RoyJ]

Jerry has asked "In a speaker designed like [ours], the crossover slopes are shallow enough so any two drivers (such as a woofer and midrange, or a midrange and a tweeter) are both operating over a significant range of the audio spectrum. As long as these drivers are not in the very same location, it is easy to place a measuring microphone so that one driver's sound arrives out-of-phase with the other driver - leading to deep suck-outs in the FR curve. This would easily explain the frequency response curve shown in fig. 2 of the review in question.

What would have been a suitable distance for the measuring mic?"


For Jerry's first paragraph, he is right in that the measurements could (and did) show suckouts. The type of measure that best reveals a suckout problem (cancellation) is best performed with a single, pure sinewave test tone at that one frequency, at that one distance and height. Move the mic just a little and the suckout at that particular tone goes away. It will re-appear on a different tone at the mic's new location.

If the mic stays in the same place and just that tone is changed by a few %, the suckout goes away. Move the mic and it will likely re-appear.

Also, at most any single test-tone frequency, reflections from one's room surfaces arrive at the mic, creating other suckouts that change with mic position even when the tone remains the same. This is what makes outdoors or anechoic testing necessary.

In the case of Stereophile's old review of our Diamante model and in the recent one of our Eos, both reviewers failed to take into account how super-far off axis the mic was from some of the drivers at his very-close-up measuring position. The result is non-flat output from the driver(s), and therefore shows frequency-response irregularities whose cause(s) essentially went unexplained to the reader.

One other important aspect-- music does not reveal if narrowband suckouts exist, since music is never pure, sustained, single tones. But if a wide frequency-range suckout shows up in one's averaged room-measurements done at a listener's distance, using steady pink noise, that can be an indication there's a problem with 'something', perhaps the speaker or the room, and probably quite audible on most music.

And to your last question-- there is no one spot nor a 'best spot' for that microphone to be placed, because it does not hear music the way we do, nor do we hear test tones the way it does. To know how to get around these problems, again please refer to my article on sixmoons. I know anyone would learn a great deal, AND there's no math! It can be found at: Speaker Measurements

Best regards,
Roy Johnson
Designer
Green Mountain Audio

 

[RoyJ]

Brief answers to short questions

Hi Jerry,

Earlier you asked "The Europas I looked at had flat fronts. Do you perhaps mean "vertically aligned drivers" or something to the effect?"


It may have not been apparent in that photo, but Europa cabinet-fronts lean back 2" out of their 18" height and also their tweeter is recessed another 1/2" behind the woofer's plane. We advised also that a listener's ears be in front of the tweeter when one is at seven+ feet away. And yes, the drivers must be vertically aligned.

For use at a closer distance, either raise the speaker or tilt it back. Instructions for what to then listen for to arrive at the 'right height' or 'the right tilt' are given in their Owner's Guide. All of this applies to our current Rio 2-way as well, but its natural cabinet-face tilt-back is greater than Europas, for placement on shorter 20" stands (instead of 24" ones). That produces an overall height more visually suited to living in smaller rooms.

Best regards,
Roy Johnson
Designer
Green Mountain Audio

 

[RoyJ]

for KEW

KEW asked, "are there some notable threads on other forums from RMAF about GMA?"

Not at this time nor ever from the 2010 RMAF, because there I chose NOT to play our speakers, as the tube gear we had committed to using was robbed of all dynamic contrasts, even at modest SPLs-- from unusually low AC voltage.

I was greatly disappointed and so were many others- a mistake on my part that will not be repeated! More information about the recent RMAF is posted on our News page.

Best regards,
Roy Johnson
Designer
Green Mountain Audio

 

[3db]

Roy

I'm not sure I beleive all I read taht you have posted. However, I do appreciate your patience, candor, and effort in explaining all of this.

 

[RoyJ]

Sound quality

Jerry, earlier you remarked that I wrote "reviewers don't care about sound quality". No, I meant reviewers don't care about time coherence. I should have made that more clear, sorry.

And yes, I really do think most speaker designers do not have an intimate knowledge of live sound.

For a speaker designer, this education must occur in perhaps a living room with a string quartet or a soprano practicing, or on stage right next to Asheknazy playing a Steinway, with Freddie Fennel conducting. And by being only a few feet from a superbly played clarinet, sax, bassoon, oboe, violin, cello, banjo, dobro, marimba, percussion, symphony orchestra and 100-voice chorale, and next to a Gibson guitar played through a Fender Twin-Reverb, each for days and weeks on end, via world-class artists (far better than the 'audiophile artists'). I have, across the span of many years, and my speakers are better for it.

From what I hear coming out of most designs, I can only surmise their designers never had these experiences. I learned more than I ever imagined and am glad I took the time!

Best regards,
Roy Johnson
Designer
Green Mountain Audio

 

[JerryLove]

Roy,

I truly do that you are here to discuss your speakers and that you are taking the time to answer so many questions. I am, however, disturbed by apparent thrust of the assertions in question. I have no desire to put words in your mouth, and certainly welcome you correcting any wrong paraphrasing here, but you seem be be saying the following things.

You seem to be asserting that no speaker designer (except yourself), no reviewer, no recording engineers, basically no one can tell that time coherence is "clearly better". I don't understand how you can assert that it is clearly better, and yet that reviewers will not hear it.

I further don't understand how you can assert that other speaker designers (Roger Russell:Lead speaker designer for Mcintosh and Electrical Engineer, or Joe D'Appolito Ph.D and chief engineer for Snell, or Dr.Floyd Toole of Harmon Kardon, or Arnie Nudell of Infinity and then Geness) lack... how did you put it? "do not know the sound of live instruments" and "do not understand the math"

Seriously? You assert that Floyd Toole doesn't know what a live instruments sounds like and doesn't understand the math involved in acoustics? The man quite literally wrote the book.

Further: in a world with single-driver headphones, single driver planar speakers, and indeed a number of single-driver floor-standers: that these same people with literally decades each in the field have no experience with coherent sound?

Beyond that: you've asserted that an industry which has experimented with and makes Walsh-cones (another with no electrical crossover BTW), ribbons, domes, inverted domes, horns, electro-static drivers, planar-magnetic drivers, air-motion transformers, and one of my favorite "neat-o" technologies: plasma; is too conservative to try placing the tweeter a few inches back?!?

And yes, I really do think most speaker designers do not have an intimate knowledge of live sound.

I'm sorry: but what I'm hearing from you flies in the face of all reasonable thought. It seems to assert that, with the exception of you personally, every speaker designer throughout history is an ignorant rube with with bad ears, no understanding of math, no experience with actual instruments and an unwillingness to experiment: this despite the fact that there are other real-world examples of exactly what you tell me no one does.

- Paul Barton of PSB is a violinist.
- Roger Russell used to bring live instruments into McIntosh's labs for evaluation and demonstration of speakers and testing equipment.
- I can't speak to the designer: but Bower's and Wilkins has been the mainstay monitor of the world's largest recording studio for more than a decade. I assume Abby Road has some experience with live music.

The thought that speaker designers have less experience with live music than I do seems absurd. Do you have something other than conjecture to back that up with?

You claim to have extensively studied the exact threshold for when phase incoherence causes a problem: but you haven't put up the studies. Your site discusses the importance of measurements to make coherent sound: but you then avoid presenting them to others to measure (indeed, making FR, waterfall, and cabinet resonance charts of your speakers available).

And this is sadly consistent with the testimonials of the new posters who showed up to post in favor of GMA. Feel free to point out where I'm wrong but not a single one said a single negative thing about any GMA speaker; nor did a single one say a single positive thing about any other speaker line.

The message being "everything GMA makes is perfection, no one else gets a single thing right"... and a message like that tends to say a lot about the messenger.

Then there's Maui-man... Someone asserting decades of recording who doesn't, even when asked, make a single plug for his work and who, when called to task (say: over phase-inverted L/R signals) simply says nothing at all.

I seriously started this thread because I was pondering buying some used Europas off Audigon to give them a listen. The only thing that really stopped me was an uncertainty about the resale-ability should I dislike them (I've done this with an awful lot of speakers the last couple years and sold the ones I didn't like)... unfortunately, GMA doesn't come up for sale much so I had no idea if I'd be able to recoup if I didn't like.

At this point, and unless there's some major change, I'm avoiding the entire line like the plague. The rampant negativism toward every other design, combined with the ridiculousness of many of the assertions has left a very bad taste in my mouth. (and I'm the the group of potential customers that has put out in excess of $20k on AV gear in the last 12 months, and one that's very vocal in promoting what I like)

Jerry, earlier you remarked that I wrote "reviewers don't care about sound quality". No, I meant reviewers don't care about time coherence. I should have made that more clear, sorry.

What's the functional difference? If coherency = better sound then a reviewer that cares about sound quality will comment positively; and if coherence doesn't = better sound than why do I care about coherence?

And to your last question-- there is no one spot nor a 'best spot' for that microphone to be placed, because it does not hear music the way we do, nor do we hear test tones the way it does.

Well that's a darn shame since everything I play on my speakers was recorded on a microphone.

I realize this post has turned into something of a rant, and I'm very sorry that it's come to that... but what 3db has called candor, I'm seeing as rhetoric.

I'll give you an easy way to counter much of the thrust of my rant:
What is it that your speakers have had to sacrifice, relative to other design options, in order to get what you felt was important to add. What is at least one of the major sonic weakness of the design you have chosen over some other design.

Ribbons, for example, tend to sacrifice low-frequency response and become very room and position dependent because of their bi-polar nature. A front-driving cone suffers off-axis performance in comparison. A uni-driver (generally) suffers a great deal of distortion from a need to do more than a single driver can do, but a multi-driver system has issues with integration, and timber-matching as well as positioning problems related to axis (sounds different when your head is tweeter-aligned than then when it's woofer aligned).

Do you assert that you have achieved perfection in sound reproduction? Or have there been sacrifices that you have had to make relative to other designs? Name at least one.

 

[Shakeydeal]

This thread has really morphed. I can't speak to anything technical about speaker design. But as I was listening to Johnny Adams on my C3s last night, I was thinking "man am I glad I bought these". I don't know how much $$ I would have to spend to better what I hear, but truth is, I don't care.

Ok, as you were......


Shakey

 

[JerryLove]

I don't know how much $$ I would have to spend to better what I hear, but truth is, I don't care.

That seems a surprising sentiment.

I'm not sure what the price on the C3 was, but let's assume it was $9k (making it the predecessor to the Pico). What if better sound was a Paradigm Signature S4 ($4k) and so the cost to better sound was -$5k?

I believe that, for most, it is the best combination of sound, ergonomics, and cost that we want to find (and we all prioritize those three differently).

*Please note: I'm not asserting that the C3's are not the best price-ergonomic-performance for you, nor indeed for anyone. I have no idea what they sound like. They may be terrible. They may be awesome.

 

[Swerd]

I asked the question about microphone placement that you answered above, not Jerry. Its an easy mistake with all the recent posts.

I just finished reading the 6moons article you linked. It was general enough so I don't have specific questions about what you said. If I understand correctly, it describes the many limitations inherent in any speaker measurement. People who have tried doing their own measurements may understand this, but those who have never done it might have lost most of your message. I have often wondered just how much magazine reviewers understand about this.

Your article suggests that the major difficulty in measuring and demonstrating the benefits of speakers 1st order acoustic crossovers is the idea that moving the test microphone slightly has a large effect of the results. I have no problem with any of that. But what happens when a listener moves his head? And how does an owner go about the complex proceedure of selecting speaker location with regard to walls and his listening position? Is there a narrow range of locations for listening to the phase-accurate and time-aligned benefits of 1st order crossovers. Do owners need a vice-grip for their heads?

I did notice that further down the page, where the article contains scanned in text and figures, it was mentioned that "the crossover is not only electrically phase-accurate but also time aligned". Any 1st order electrical filter will accomplish that. What matters to listeners is the acoustic performance of the speakers when they are wired to the crossover. Is their acoustic behavior also phase-accurate and time-aligned? This is more difficult to achieve.

Underlying your design philosophy about 1st order crossovers and their potential for time-alignment and phase-accuracy, is the idea that humans can detect differences between speakers that are time-aligned and those that aren't. Likewise for phase. If I understand the present knowledge of human sound perception (and I am not a professional in this area), this subject is undecided. Scientifically it is considered controversial. There is not enough evidence for most scientists in the field to consider this idea as a settled matter. What is your evidence that differences in time-aligned and phase-accurate loudspeakers are audibly detectable? And do these differences lead to the perception of better sounding music?

There I managed to avoid the subject of math . I stopped my math exposure at college physics 101 and differential equations. I doubt if I could even nod my head intelligently at that subject today, much less anything above that.

I'm enjoying reading all this so far. Thanks Roy.

Richard

 

[TLS Guy]

I have been watching this thread with interest.

A few issues have been glossed over.

The problem of getting accurate data from a measuring microphone is actually highlighting a significant problem with a speaker using spaced driver and first order crossover. The fact is that you can get measurements you want or dislike with small variations of the test position.

Why because there is broad driver over lap and lobing issues with a highly asymmetrical lobing pattern.

Now I built a speaker system which I still use as my rear backs in 1884. This largely uses first order crossover in a stepped array speaker pattern.

The lowest crossover at 180 Hz is third order, as a first order solution at that point was impractical for many reasons, especially power distribution, but many other reasons.

The problem was that this is a very difficult nut to crack and the finally crossover design took 10 years, with a lot of help from the king folks at Dynaudio.

Now in my old environment I was the main user, and I could set the speaker drivers at the optimal height and put the fix the listening position to minimize the lobing errors.

Within the above limitations the system works very well.

Why did i do this? I was coming out of my full range driver era.

I did a lot of recordings at that time using minimalist mic techniques. I used the MS technique, so mono listeners got a perfect mono experience.

Did this speaker system show multi kiked recordings in an unfavorable light, yes!

Did I do this with my new studio fronts? No. Why? Because a full house needs a good experience. I don't care what anybody says, but a spaced driver array with first order crossovers can not do that. It is impossible.
However I do not play loose and fast with phase either like a lot of designers do.

What data do we have. Well the most time and phase coherent speaker is the Quad ESL. Two can cancel a square wave in free space.

However listening tests with that speaker with introduced phased shifts did not achieve statistical significance.

What we don't know is what would have happened if only coincident mike recordings had been used.

 

[RoyJ]

Correcting misconceptions, if possible!

Hi Jerry,

You wrote "I pointed out that the Europa's front was flat, though not vertically aligned (in other words, that they were at an incline relative to a plane perpendicular to the floor) and you countered by telling me that I may not have seen it but it was inclined." Sorry- yes, its front face is flat. The mechanical time-alignment is taken care of by the tilt-back, by the tweeter's additional setback, and by recommending where the listener's ear goes.


Continuing with your thoughts:
"You seem to be asserting that no speaker designer (except yourself), no reviewer, no recording engineers, basically no one can tell that time coherence is 'clearly better'. I don't understand how you can assert that it is clearly better, and yet that reviewers will not hear it."
I did not assert no one can hear it, but that very few people have ever heard time-coherence done right, across the tone range. Anyone can hear the sound is better, in every way, given the opportunity.


Regarding other transducers that are time coherent: Certainly the Ohm A and F came close enough, but long ago. The Soundlab full-range electrostats do it to the same level we do. Dahlquist and Spica models never were time-coherent, despite all assertations. Quads-- not really. Arnie Nudell came close in several designs. d'Appolito designs- none I know of. I'd forgotten about Paul at PSB, and please judge his non-time-coherent results. A few afternoons with live instruments for Mr. Russell's situation I know is not enough. I remind you not everyone has excellent hearing, deviating from the norm as with other senses. Regarding the folks at Abbey Road, who knows what they heard, and what political pressures came to bear.

From all of his writings, I see that the honorable and much-respected Floyd Toole understands deeply only the amplitude-math of acoustics and speaker design. I asked him directly at a seminar here in town about five years ago if he thought time-coherence mattered, and he said "No" in front of the entire audience. Go figure.

It is ONLY my opinion that many designers must not know the sound of live instruments, and I said why I believed so. Have a look at other designers' bios, if you can find them, to find out if they mention extended periods of live-sound experience with all sorts of music, and not 'by being out in the audience'. Find out if they have worked long hours with all sorts of recording microphones to know how those change 'the absolute sound' and then throw in the changes mic preamps, mixers, and recorders add.... Sorry if my opinion upsets some people-- I don't play politician as well as might be necessary.


I have extensively used and worked with the Hill Plasmatronics speaker system and separately with its tweeter module, which did come with an active first-order crossover box. The sonic result with a different mid was literally indistinguishable from what I was already getting from my four-way design at that time. Unfortunately, Dr. Hill's crossover to his woofer and mid had severe time-delays and that always colors what any tweeter/mid time-coherent blend is doing.


And Jerry, please know that placing the tweeter a few inches back is not even close to 'trying for time coherence'. Whomever told you so did not learn about the phase shifts (time delays) crossover circuits create.


Jerry, you ask "You claim to have extensively studied the exact threshold for when phase incoherence causes a problem: but you haven't put up the studies?" Jerry, I ask why I should put up my proprietary studies? My goal here is not to persuade anyone about the sound of our speakers without listening to them, but only to explain my technology and illuminate some of the poorly-understood aspects of speaker design.

One could review virtually every comment on the internet made about our sound, and you'd find almost no one who disagrees with what I and my retailers hear. But their comments are not based in science, something that perhaps this forum encourages. Then again, none are speaker designers, so why should they know the science?

However, near the beginning you wrote "The question with Green Mountain is "does the speaker itself deliver?"... I imagine my curiosity will remain unsatiated until I run across someone who has some setup I can listen to."
Exactly my expectation, thanks. Purchase those used Europas. The price offered is great and the Owner is one I know to be a good guy. Europas have been re-selling at the same 2/3rds of original retail for five years after being discontinued (there's a reason for that), if this is of any encouragement. Just remember, they are meant for smaller rooms, less than ~15 feet wide, if you expect any low bass.


You wrote "...the testimonials of the new posters who showed up to post in favor of GMA. Feel free to point out where I'm wrong but not a single one said a single negative thing about any GMA speaker; nor did a single one say a single positive thing about any other speaker line. The message being "everything GMA makes is perfection, no one else gets a single thing right"... and a message like that tends to say a lot about the messenger."
If that's what you choose to believe was their message.


I saw their responses as being highly pleased, in ways meaningful to music and their pleasure. Ask them yourself if they have anything negative to say, please! And perhaps they do not have anything to say about other speakers-- no one asked anyone but ShakeyGround, and he printed quite an imposing list:
Von Schweikert VR4 Silvers
Magnepan 1.6 with heavily modified outboard xovers
ACI Jaguars
PBN Montana SP2
Meadowlark HR Shearwater
Reimer McCullough
Silverline Sonata II
Magnepan 3.5
Von Schweikert VR4 Gen III HSE
PBN Montana EPS2
Piega P-10
Wilson Audio Specialties Sophia
Coincident Super Eclipse

Surely this list must mean something? How many reviewers or forum members have lived with such a wide range of speakers?


Jerry, you wrote that "At this point, and unless there's some major change, I'm avoiding the entire [GMA] line like the plague. The rampant negativism toward every other design, combined with the ridiculousness of many of the assertions has left a very bad taste in my mouth."

OK-- your loss. On the other hand, I am well-known for not pissing people off and I apologize if I gave you a bad taste. I was not being negative about other speakers, but pointed out their lack of time coherence, which is quite true, and listed the many reasons why I thought that was so, including my reasoned opinion about why other designers do not seem to hear via not experiencing enough live music up close. And, please which of my assertations do you find ridiculous-- that one can hear the difference time coherence makes when the speaker is free of other common flaws? That anyone can hear a change in our tweeter's position by an eight of an inch? If these are hard to believe, I understand, but that does not make my assertations 'ridiculous'.


Jerry, you ask "What's the functional difference? If coherency = better sound then a reviewer that cares about sound quality will comment positively; and if coherence doesn't = better sound than why do I care about coherence?" Quite true, but most all reviewers have never heard time coherence, especially from speakers with simple crossovers, because no one else makes them!


I had written "there is no one spot nor a 'best spot' for that microphone to be placed, because it does not hear music the way we do, nor do we hear test tones the way it does" and Jerry's response was "Well, that's a darn shame since everything I play on my speakers was recorded on a microphone". I see that I left out the word 'measuring' as in "no one best spot for the measurement microphone to be placed". My apologies.


Geez, you guys ask some good questions!
As an example, Jerry, in your last post you ask "What is it that your speakers have had to sacrifice, relative to other design options, in order to get what you felt was important to add. What is at least one of the major sonic weakness of the design you have chosen over some other design."

I have sacrificed being able to choose from a wide range of drivers, and from having to manufacture odd cabinet shapes. I don't hear nor do I measure any sonic or performance weaknesses in ANY area, thank goodness.

Yet, I'd be a fool to claim perfection, in fact I'm happy to tell you I've many times gone out of my way to explain why perfection cannot be possible from manmade devices.


Jerry, you go on to state "a multi-driver system has issues with integration, and timber-matching as well as positioning problems related to axis (sounds different when your head is tweeter-aligned than then when it's woofer aligned)." My answer to the first two parts is "No, if the designer knows what he is doing." To the latter part- I design speakers to sound best when one sits down to listen deeply and/or critically. That is what sets my design axis for any woofer/tweeter alignment. I hope I answered what you asked!


Shakey's C-3 speakers were $17k with upper grilles when discontinued 4+ years ago. The later, HD-modified version Shakey possesses would now retail for about $20k, but we can no longer obtain their mid driver or an equivalent that will put up with first-order crossovers at 280Hz and at 3kHz.


FWIW, I do list some of our driver suppliers on our website. Driver design is its own specialty, requiring a lifetime to master, and I doubt if I will ever attempt it. Even so, a company that manufactures a superb tweeter often cannot make an equivalent mid or woofer. This is born out, in my opinion/experience, when I see complex crossover circuits employed to 'correct' the shortcomings of drivers.

Thanks for all the questions, especially from Mr. Jerry. You all have a great weekend!

Best regards,
Roy Johnson
Designer
Green Mountain Audio

 

[RoyJ]

Swerd remarked:
"I just finished reading the 6moons article you linked. It was general enough so I don't have specific questions about what you said. If I understand correctly, it describes the many limitations inherent in any speaker measurement. People who have tried doing their own measurements may understand this, but those who have never done it might have lost most of your message. I have often wondered just how much magazine reviewers understand about this."

From my experience, none. Which some here could take as an insult, but it is meant only as an observation after 20 years of contact with reviewers and editors. Then again, I don't know what a physician knows... we each have our limits.


Swerd continues:
"Your article suggests that the major difficulty in measuring and demonstrating the benefits of speakers 1st order acoustic crossovers is the idea that moving the test microphone slightly has a large effect of the results. I have no problem with any of that. But what happens when a listener moves his head?"

On music, much less than what certain test graphs would indicate. In our speakers, one mostly hears a shift in tonality with some loss of depth when moving vertically.


"And how does an owner go about the complex procedure of selecting speaker location with regard to walls and his listening position? Is there a narrow range of locations for listening to the phase-accurate and time-aligned benefits of 1st order crossovers. Do owners need a vice-grip for their heads?"

Our setup is quite easy, and described in our Owner's Guides, and it is similar to most other speakers. Everyone feels little restriction in their head movement. I can say why, if that matters.


"I did notice that further down the page, where the article contains scanned in text and figures, it was mentioned that "the crossover is not only electrically phase-accurate but also time aligned". Any 1st order electrical filter will accomplish that. What matters to listeners is the acoustic performance of the speakers when they are wired to the crossover. Is their acoustic behavior also phase-accurate and time-aligned? This is more difficult to achieve."

Kind of a mis-statement in the review. What was meant is that our crossovers have little electrical phase shift to the amplifier- i.e., the speaker's impedance appears mostly resistive to the amplifier, which has nothing to do with a speaker being time coherent. First-order filters alone cannot give a smooth impedance curve, as the raw drivers' impedance variations 'show through'. You are partially correct in that it is the final acoustic performance that matters- it is the final acoustic wave that must show the lack of phase shift.

"Underlying your design philosophy about 1st order crossovers and their potential for time-alignment and phase-accuracy, is the idea that humans can detect differences between speakers that are time-aligned and those that aren't. Likewise for phase."

I would interrupt here by noting the word 'phase' is confusing. A speaker can be in-phase but not time-coherent. The converse is that a time coherent speaker is always 'in phase' among its drivers. Sorry for the interruption--

"If I understand the present knowledge of human sound perception (and I am not a professional in this area), this subject is undecided. Scientifically it is considered controversial. There is not enough evidence for most scientists in the field to consider this idea as a settled matter. What is your evidence that differences in time-aligned and phase-accurate loudspeakers are audibly detectable? And do these differences lead to the perception of better sounding music?"

The evidence is clear to me, and remember, most people with physics backgrounds choose to make actual income in fields other than audio, so it is little wonder our industry languishes... For us, the evidence is in the listening, which is the only reason we have survived this long in such a strange marketplace, one with very low barriers to entry for anyone wanting to make speakers, as the economists and MBAs say! Yes, better-sounding music is the result of time-coherence done right.

I'm glad to know you're enjoying this, Richard, thanks!

Best regards,
Roy Johnson
Designer
Green Mountain Audio

 

[RoyJ]

TLS Guy,

Is there anything I can clarify?

Best regards,
Roy Johnson
Designer
Green Mountain Audio

 

[GranteedEV]

Roy, if discussion in this thread continues, could you do me a favour and use quote tags? They make extensive posts much easier to read. Thanks.

 

[bocat57]

If I May Jerry

And this is sadly consistent with the testimonials of the new posters who showed up to post in favor of GMA. Feel free to point out where I'm wrong but not a single one said a single negative thing about any GMA speaker; nor did a single one say a single positive thing about any other speaker line.

It was my understanding that this thread started because you wanted to hear about green mountain speakers. I wrote 2 posts to tell you that I really like my Rio's. In the above quote you imply that my posts were flawed in some way. I only did what your original post requested. You wanted some input on the green mountain and I tried to help and now I feel as if you are questioning my integrity.

I am not an audio reviewer. I am a stationary engineer. I haven't had lot's of different speakers to compare sound quality. In fact I have only had 2 pairs of high end speakers since 1992. ( not including my Rio's ) The Rio's have blown both of them away.


I may not be an audio reviewer and don't understand most of the technical stuff on this thread but one thing I do know is listening to music. Through the years of listening to music and reading audiophile magazine reviewers. I have have learned how to listen to music.

Like I said I do not understand the technical mumbo jumbo and I really don't care if I ever do because in my mind it's all about the music. I listen to all kinds of music all the time. (Jazz-Rock-Classical-Blues) You see to me it's all about the music and like I tried to tell you the Rio's are all about the music.
If I wrote nothing negative about the Rio it's because I don't have nothing negative to write about them.

The Rio's are very musical. I listen to them (along with the rest of my stereo )
for hours and hours,all the time. I know that I got a great stereo (the Rio's are a critical part) I know because when I am listening I forget all about the gear and just focus on the music and thats the way it should be.

I hope you can believe me but if you don't thats ok. It's your loss I know what the green mountain experience is !

Bob
New York

 

[JerryLove]

Hi Roy,

In my opinion, the majority of audiophile-magazine reviewers are not well-qualified nor experienced, so we do not seek reviews from most publications

I did not assert no one can hear it, but that very few people have ever heard time-coherence done right, across the tone range. Anyone can hear the sound is better, in every way, given the opportunity.

Perhaps you'll understand my confusion between your two posts above.

Ignoring the issue of measured tests: if your speakers offer a clearly superior result which "anyone can hear": why would sending evaluation units to reviewers not result in a large number of positive reviews?

Regarding other transducers that are time coherent: Certainly the Ohm A and F came close enough, but long ago. The Soundlab full-range electrostats do it to the same level we do. Dahlquist and Spica models never were time-coherent, despite all assertations. Quads-- not really. Arnie Nudell came close in several designs. d'Appolito designs- none I know of. I'd forgotten about Paul at PSB, and please judge his non-time-coherent results. A few afternoons with live instruments for Mr. Russell's situation I know is not enough. I remind you not everyone has excellent hearing, deviating from the norm as with other senses. Regarding the folks at Abbey Road, who knows what they heard, and what political pressures came to bear.

I fear you are responding to two (or more) different portions of my comments. In one case I was responding to your statement that other speaker designers lacked experience with live (unamplified) performance. In another case I was responding to your assertion that companies are unwilling to produce unorthodox designs. In yet another I was responding to your assertion that designers lack exposure to phase-coherent design.

I do appreciate that you made a positive statement about another design in there. As to PSB: I have a pair of 400i's on my PC... they have very pleasant vertical off-axis performance which is important to me because they are well above ear level and not angled down.

It is ONLY my opinion that many designers must not know the sound of live instruments, and I said why I believed so. Have a look at other designers' bios, if you can find them, to find out if they mention extended periods of live-sound experience with all sorts of music, and not 'by being out in the audience'. Find out if they have worked long hours with all sorts of recording microphones to know how those change 'the absolute sound' and then throw in the changes mic preamps, mixers, and recorders add.... Sorry if my opinion upsets some people-- I don't play politician as well as might be necessary.

I was unaware you had a such long history in music production. Are your audio productions commercially available?

And Jerry, please know that placing the tweeter a few inches back is not even close to 'trying for time coherence'. Whomever told you so did not learn about the phase shifts (time delays) crossover circuits create.

I believe you are responding to a question I asked, not a claim I made. Unfortunately, because of that apparent confusion, you did not actually answer the question.

Jerry, I ask why I should put up my proprietary studies? My goal here is not to persuade anyone about the sound of our speakers without listening to them, but only to explain my technology and illuminate some of the poorly-understood aspects of speaker design.

Take your pick: credibility, notoriety, advancing the state of the art, product sales, posterity.

I suppose if I understood the reason why you would *not* publish your data: I could better suggest a motivation to publish your data. My familiarity (by reputation more than study) of the real subjective affects of off-axis linearity, cabinet resonance, harmonic distortion, directionality, indeed such basics as wire gauge is that they are available.

This would seem to put you in the minority when it comes to publishing results.

Exactly my expectation, thanks. Purchase those used Europas. The price offered is great and the Owner is one I know to be a good guy. Europas have been re-selling at the same 2/3rds of original retail for five years after being discontinued (there's a reason for that), if this is of any encouragement. Just remember, they are meant for smaller rooms, less than ~15 feet wide, if you expect any low bass.

My problem is "and what if I don't like them?". There's no much of a used market for GMA, so reselling could be a problem.

Mind you, I've spent far more on speakers I had never heard (indeed no one had) based on measurements and reputation. Interestingly enough with someone I hotly debated (And I continue to contend that the presence of reflections cannot improve actual fidelity). But I digress

Surely this list must mean something? How many reviewers or forum members have lived with such a wide range of speakers?

More than I think you suspect.
*Some* of mine
Paradigm Studio 40v3
Paradigm Studio 60v3
Paradigm Signature S2v1
Monitor Audio Gold Bookshelves (forget model)
PSB 400i
Ohm Walsh F
Infinity RSIIb
McIntosh XR-5
McIntosh XD-717
B&W DS-6
B&W LM-1
B&W 801 Series 2
B&W 801 Nautalus
Infinity Primus 362
(heavily modified) Infinity Primus 360
Kef Q1
A/D/S towers (forget the model)

That's just in my house, that's all recent. I've spent many an afternoon out listening to other gear.

OK-- your loss.

I would think the loss would not be restricted to me there.

And, please which of my assertations do you find ridiculous-- that one can hear the difference time coherence makes when the speaker is free of other common flaws? That anyone can hear a change in our tweeter's position by an eight of an inch? If these are hard to believe, I understand, but that does not make my assertations 'ridiculous'.

That all other speaker designers "have never heard [time coherence] without complex crossover circuits." - when they have planar speakers, unidriver speakers, and headphones.

That they "do not know the sound of live instruments".

That all other speaker designers "do not understand the math"

That the "majority of audiophile-magazine reviewers are not well-qualified" to say 'hey: these speakers sounded awesome'.

That speaker companies are unwilling to make cabinets without fully vertical fronts.

That consumers or manufacturers find non-square cabinets unacceptable.
http://www.bang-olufsen.com/loudspeakers
http://www.bowers-wilkins.com/display.aspx?infid=1460&sc=hf
http://www.anthonygallo.co.uk/pages/products.php
http://www.svsound.com/products-sub-cyl.cfm
http://www.martinlogan.com/product-list.php

etc. etc. etc.

Quite true, but most all reviewers have never heard time coherence, especially from speakers with simple crossovers, because no one else makes them!

So you send them a pair and they write awesome reviews, buy some for themselves, and spend the rest of their career saying "these new speakers were nice, but couldn't compare to my reference Green Mountain speakers"

Step 3: profit.

I have sacrificed being able to choose from a wide range of drivers, and from having to manufacture odd cabinet shapes. I don't hear nor do I measure any sonic or performance weaknesses in ANY area, thank goodness.

Yet, I'd be a fool to claim perfection, in fact I'm happy to tell you I've many times gone out of my way to explain why perfection cannot be possible from manmade devices.

So they lack any weakness but are not perfect? That doesn't appear to make sense.

FWIW, I do list some of our driver suppliers on our website. Driver design is its own specialty, requiring a lifetime to master, and I doubt if I will ever attempt it. Even so, a company that manufactures a superb tweeter often cannot make an equivalent mid or woofer. This is born out, in my opinion/experience, when I see complex crossover circuits employed to 'correct' the shortcomings of drivers.

Thanks. I'll go look them up. I'm curious to see (some of) what you are using.

 

[JerryLove]

It was my understanding that this thread started because you wanted to hear about green mountain speakers. I wrote 2 posts to tell you that I really like my Rio's. In the above quote you imply that my posts were flawed in some way. I only did what your original post requested. You wanted some input on the green mountain and I tried to help and now I feel as if you are questioning my integrity.

Go to http://forums.audioholics.com/forums/showthread.php?t=64773. Check posts like #5, #7, #13, #14. Notice that even great fans point out the weakness of a speaker as well as its strength.

Notice in post #17 where the poster makes a comparison to other speakers. Note how different this is from Shakey's comparison in this thread that the GMA makes the other speaker "sound like crap".

I questioned the veracity of the appearance of several posts from newly registered accounts which uniformly describe the object in question in a way different from how most other posts describe most other things.

I cannot imagine why a grown adult would take it personally. I would imagine that they would find it rather understandable and either move on or attempt to rectify it by offering up a more nuanced post. I don't think it would be reasonable to say I questioned your integrity when I have no idea who you are. It might, however, be accurate to say I questioned your existence.

I hope you can believe me but if you don't thats ok. It's your loss I know what the green mountain experience is !

So you've never heard any speaker that in any way had any advantage over your GMA speakers?

I would think one immediate disadvantage would be that they are mono-polar speakers. You won't get room reflections as complete as occurs with omni-polar and bi-polar rigs. Another obvious compromise vs. other speakers (planars and column arrays) would need to be the rate of sound drop-off. Volume on a GMA speaker will be more affected by distance than off a Maggie, or ML, or McIntosh XR2kt. Again: this is an inevitable trade-off with the choice to use individual direct-drive cones and domes.

Would you agree with those statements? Would you agree that the performance of your GMA speaker at 180-degrees off-axis is inferior to a Magipan 1.6? Would you similarly agree that the sweet-spot is smaller?

 

[3db]

From my admittedly weak understanding, it would appear that the designs of the Green Mountain Speakers offer such a narrow sweet spot that tilting your head to one side signifcantly alters the sound one hears. Not so with my PSBs. If that is the case, please keep your speakers. When I sit down to listen to music, I don't want to have my head held in a vice to achieve ultimate sound. Thats not listening. Thats entrapment. and not mention down right uncomfortable. Furthermore, these speakers would absolutely fail in a home theater application where wide dispersion is required to fill the room with subtle ambiance.

 

[Shakeydeal]

Would you agree with those statements? Would you agree that the performance of your GMA speaker at 180-degrees off-axis is inferior to a Magipan 1.6? Would you similarly agree that the sweet-spot is smaller?
__________________

What does it matter if the sound is worse off axis? Where do you do most of you listening?

And no, the GMA speakers do NOT have a smaller sweet spot than a maggie 1.6. Not many speakers do.

Shakey