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With a fairly long thread going on over in the speaker forum on absolute phase/polarity I got to thinking (always a dangerous thing) and wondered just how big the difference is when you flip polarity. As most pros say the biggest difference is with kick drum, I got a pretty good wav file of a kick hit and made a new track repeating the hit 5 times, then 5 times with polarity reversed, then back, and so on. I posted the wav file in an open dropbox folder - the link is below. The 1st pic shows the waveform going from a normal hit to the reversed polarity hit. The 2nd pic shows a detail of the hit waveform.
I can't hear a difference. Can you, or am I missing something?
Also, looking on the detailed waveform, I wondered about that first full cycle of the waveform in front of the biggest peak. When I cut that first cycle out, the hit sound became dull dull dull -- it lost all its character. Apparently a kick drum being hit is a pretty complicated thing.
WW
New Orthophonic High Fidelity
Follow Ups:
Well, cutting of the wave form at the beginning, you just discovered the relevance of slew rate in naturally occurring sounds. It shows how the ear perceives an impending sound. The rate of rise determines and gives the ear reference for the upcoming attack of a sound; the brain needs the cue to process the pending transient.
Us engineers know this. This is why they have attack controls on dynamics processors. By allowing that part of the signal you cut out to pass at a higher level gives the ear a louder "cue" and you perceive more higher transients even though the level of the highest part is actually being limited.
So the next time you hear an audiophile argue slew rate is not perceivable or important to music, you know better.
The interesting thing about slew rate that was discovered back in the 80s was that higher slew rates don't translate to better sound as one might expect. Actually the opposite. Kinda like the THD thing. If high slew rate was the answer we'd all have very high slew rate amplifiers.
Do you have a reference for that?
I know the 70s papers showing the opposite (http://www.shabad.ru/IEEE/otala.pdf, http://jockohomo.net/data/7470.pdf, etc).
The papers you linked to show no such thing - they do not show that the sound improves with increasingly higher slew rates. One article simply gave a range of "safe" slew rates for amps. Higher and higher slew rates don't guarantee better sonics any more than vanishing low THD insures better sound. That's kind of the whole point. If that were true everybody and his brother would be cranking out amplifiers with extremely low THD and very high slew rates.
Edits: 10/17/13
You must have misread my question.
The Otala work shows that there is a "good enough" bandwidth, below which distortion occurs due to the feedback loop.
But you said there's work in the 80s that shows "higher slew rates don't translate to better sound... actually the opposite". I don't know that work. Can you point to references?
I'm afraid you misread my post, too. What I said was that it was discovered that higher slew rate didn't correspond to better sound. I didn't intend to suggest there are studies, particularly technical studies. I suspect it would require someone who has moderately good listening skills to appreciate the trade-off of sound and slew rate.
That's all I'm looking for. Back it up? I'm interested. How could I find out more about that? Do you have any direction to point me in?
I can only suggest Googling "amplifier slew rate and sound quality." You should find a number of discussions on various forums, perhaps other sources.
Well, then I guess us guys who actually engineer all these recording you listen to don't understand it either.I could point to several (no numerous actually) text books that have this information and how slew rate determines the ears ability to perceive postliminary transients. However, if you guys wanna talk about what other hobbyists believe by all means, look it up on some other forum online.
And the THD thing, you are dead wrong. At least that's what I discovered at the MIT Acoustics Lab, and 27 years engineering in the audio world, and having worked designing power supplies for amplifiers including Mark Levinson in the early 80's.
But go ahead, believe what you like. :-)
Edits: 10/17/13
!
The Mind has No Firewall~ U.S. Army War College.
"Over the years, Spectral's engineering talents have explored every nuance of designing an almost "infinitely fast" amplifier. Very fast slew rates, very short rise and settling times, very broad bandwidth, very swift input-to-output propagation: these are some of the critical factors which help to achieve the most perfect tracking of the music signal and the lowest possible distortion."
I especially like their having explored every nuance of designing an almost infinitely fast amplifier. Lol
You could provide numerous articles, but you didn't. You are simply being argumentative. Furthermore, I'll take almost any tube amp with .05% THD over a Mark Levinson any day. :-)
You are only making understanding slew rate limiting and its effects more difficult to get right, Geoff.
It's quite possible I overstepped my authority.
Try a Trombone signal - more asymmetric than a kick drum. I'll try to post something somewhere.
Three most important things in Audio reproduction: Keep the noise levels low, the power high and the room diffuse.
Trombone, eh? Next time I'm in the studio on a slow day I'll dig in the archives and listen to different instruments and kinds of music. The system there is pretty good at resolving, with either the Yammy NS10s or ProAC Studio 100s. (I know, the NS10s aren't something I'd choose to listen to at home, but they do bring out little stuff buried deep in the mix that everything else seems to gloss over.)
WW
New Orthophonic High Fidelity
With a resolving system, the polarity issue is huge when listening. Unfortunately the recording industry hasn't always considered it important to get the polarity right, so most recordings are in the proper polarity, but once in a while one is completely reversed.
I would have thought this topic to be beaten to death and well-understood in professional circles by now. Surely, the AES and/or the ASA must have numerous papers on it. It wouldn't surprise me if the old Bell Laboratories have archives about it.
So, why are audiophiles still debating it, instead of simply looking up the research and reading it?
:)
There is actually not much in AES and ASA. In a nutshell, polarity inversion is audible, yes, with selected signals, but overall not excessively important.
Below a list of papers and articles I have in my archive. If interested, mail me for a copy.
Klaus
Craig et al., “Effect of Phase on the Quality of a Two-Component Tone”, J. of the Acoustical Society of America 1962, p.1752
Greiner et al., “Observations on the Audibility of Acoustic Polarity”, J. of the Audio Engineering Society 1994, p.245; Comments, JAES 1995, p.147
“While polarity inversion is not easily heard with normal complex musical program material, as our large-scale listening tests showed, it is audible in many select and simplified musical settings. Thus it would seem sensible to keep track of polarity and to play the signal back with the correct polarity to ensure the most accurate reproduction of the original acoustic waveform.”
Greiner et al., “A quest for the audibility of polarity”, Audio Magazine, Dec. 1993, p.40
Heyser, “Polarity convention”, Audio Magazine, Sept. 1979, p.18
Hilliard, “Notes on How Phase and Delay Distortions Affect the Quality of Speech, Music and Sound Effects”, IEEE Transactions on Audio, March-April 1964, p.23
Johnsen, “Proofs of an Absolute Polarity”, Audio Engineering Society paper 3169 (1991)
Knight, “Report of an Ad hoc meeting on the formation of an AES technical committee on audio polarity”, JAES 1981, p.528
Lipshitz et al., “On the Audibility of Midrange Phase Distortion in Audio Systems”, JAES 1982, p.580; Comments, JAES 1983, p.447
“The important point is that there is a well-established mechanism in the inner ear for detecting waveform asymmetries and hence polarity reversal of asymmetric signals. What is perhaps surprising is how subtle this effect generally appears to be on music and speech. As the above-mentioned experiment [13] indicates however, it is an audible factor, and should be taken into account when performing comparisons of audio components [15], [19], [20] -- acoustic polarity should be maintained.”
Long, “Polarity in absolute terms”, Audio Magazine, Aug. 1989, p.14 [about Clark Johnsen’s book “The Wood effect”]
Long, “Upside down – Find out whether you can hear polarity inversion ”, Audio Magazine, July 1996, p.35
They must be polarity coherent (all drivers wired in same polarity) with minimal or no crossovers. Took me decades to own speakers that would reproduce polarity changes so obviously audible that it would force me to get a preamp with a polarity switch on the remote.
Hey Klaus, there are some pretty knowledgeable folks in that list! Thanks for posting those references!
:)
You are correct, the late Richard Heyser (passed away about 27 yeas ago) both proposed a way to measure acoustic phase but also related that to how phase shift alters a loudspeakers behavior in time.
You can probably find some of his papers on line like “determination of loudspeaker arrival time” Audiophiles debate this topic because how loudspeakers work can be confusing if you don’t have a way to measure what they do.
Magazines generally are not sources of technical information, they are marketing agents. The phase shift is not a feature, it is more or less unavoidable without dsp and so isn’t discussed very much.
We are not that sensitive to absolute phase in part because loudspeakers themselves in general do not preserve time or phase very well.
For example, a vented box exhibits a 360 degree phase rotation in the span from above to below the low frequency corner.
This means the lower frequencies are always delayed, as much as one entire cycle going from well above to below the lf corner in it’s response. This is why a sealed box preserves time better than a vented box with the same lf corner, the sealed box has half the phase shift around its low corner
The phase shift alters the harmonic time structure of a complex signal, a signal fed into it appears to be produced at different times which is not what the input signal did.
Making it more complicated, a perfectly located upper and lower drivers have a crossover to separate the frequencies. Above a first order filter ALL the normal crossovers types like Butterworth, Linkwitz and so on ALL exhibit phase shift going from above to below the crossover point.
For example, a 4th order filter also has 360 degrees of phase rotation and so the lower frequency range emerges later in time than the hf portion. It is not uncommon for a traditional loudspeaker to have hundreds even thousands of degrees of acoustic phase shift top to bottom and so the idea of preserving the input signal is out of the question.
If you can't produce all the frequencies in question at the same instant in time, then you have no way to judge absolute phase because the loudspeaker can’t preserve that over a significant bandwidth.
In spite of other shortcomings, this is why small full range speakers are popular, they don’t normally show that degree of crossover phase shift and so do a better job preserving the time related things like acoustic phase.
A loudspeaker that has flat amplitude and phase over a broad band, is the only type that can actually reproduce the wave shape of the input signal and then a square wave is a wave shape that is easily recognizable on an oscilloscope and in electronics was often used as a test signal..
VERY VERY few loudspeakers preserve time well enough to reproduce a square wave over a broad bandwidth and over a range of radiation angles.
Hope that helps
Tom Danley
~!
The Mind has No Firewall~ U.S. Army War College.
...a book that's been on my audio shelf for twenty-five years: The Wood Effect. Imagine, twenty-five years ahead of its time! There's a section on Richard Heyser in it too, including an interview IIRC. Also it chases down nearly every reference to absolute polarity in print until then, starting with an article JASA and even including double-blind tests! (For all the good that ever does... lol)
P.A.
PS It ain't cheap below, so leave me a message here for possible word on a hidden stash.
There is a test for transducers. Loo at Stereophile's Step impulse test and measurements. Stereophile, themselves downplay the results, uttering such platitudes like the "downward slope of the tweeter blends smoothly into the inverted midrange driver".
Such nonsense. In their own (Atkinson's) explanation, the graphed measurement should look basically like a right triangle: with a sharp rise time and a slow decay. Aktinson, himself, writes That he has seen such graphs only on ten (!) models from 5 manufacturers (Thiel, Vandersteen, Quad, Dunlavy, and Spica.
With even well regarded systems like Wilson displaying such appalling performance, it is no wonder that absolute polarity can not be heard by most, Inverting polarity basically become half a dozen of one and six of another.
One notable speaker designer put it very well ( he is on the Atkinson list, BTW). And I quote "if perfect frequency response and time alignment and phase alignment were the goal of every manufacturers and designer, shouldn't there be a convergence of sound at a particular price point?"
I am fortunate that haved owned Spicas, Vandersteens, Quads, and Thiels. For me absolute polarity is clearly audible, because I modify my speakers within 90 degrees of being time aligned.
Of course YMMV
Yup, lots of insight and good info you wrote there, Tomservo.
With regard to multi-way speaker systems, I'm hoping - as I finalize the design of my new ones - that I'll be able to ($$) incorporate appropriate time delay with the crossover in order to reduce some of that phase delay problem (they'll be tri-amped). I know Rane and dbx have some capabilities in that area, but I haven't looked into it in a couple years - since there have been other issues to work out, and a more-or-less normal life to lead.
Heyser really knew what he was doing. It's so great when a person almost intuitively understands the acoustical, mechanical and electrical physics of audio, AND is in a position to produce and publish high quality research. He and a couple handfuls of other folks were the giants who got us to where we understand most of what we do in audio.
Can y'all say TDS and TEF?
:)
You can't fix a group-delay problem with a single time-delay for a given band. The delay is frequency dependent. Some DSP/active boxes have phase correction, and the Thuneau Allocator computer-based DSP crossover has phase correction which it does with what they call "forward/reverse processing". It's kind of cool. By virtue of a latency delay, the process effectively "goes forward in time" (a trick using the latency delay) and causes in effect the opposite of group-delay. Sort of a group-"opposite of delay". Then, the crossover function causes the expected group-delay which in effect cancels out. So yes, you can make pretty square waves with standard filters such as 3rd order Butterworth and 4th order Linkwitz riley. The only trick is you need to know the acoustic function and Fc points for all crossover points, and the -6db point for the LF band, if ported. (This is to do with the group-delay of the ported design Tom was referring to).
Fascinating stuff.
Cheers,
Presto
The trouble is they are all about measurements. It wouldn't surprise me too much if nobody in either organization has any idea what he's listening to or has ever tried to hear the difference in polarity. And since they aren't standards groups they presumably would have no real concern about polarity one way or the other.
I've been an AES member for decades. Its focus is the sound, as well as the role of measurements in designing and evaluating gear, studios, pro sound installations, and broadcasting. If you dig into the AES e-library, you will find a huge concern with the relationship of measurements to what we hear. (They have a bunch of Heyser's papers for example. Also, their big-deal event at the annual conference is the Heyser memorial lecture.) The other giant organization, the IEEE, *is* more concerned with standards, but then standards is their business.
BTW, for audio geeks in New York, the AES convention will be at the Javits center Oct 17-20. A ticket to the full conference is expensive, but you can fill up four long days from the couple hundred technical sessions they offer. You can also meet and talk with the engineers, producers, designers, and manufacturers. There are studio visits available during the run; Electric Lady Studios and WQXR come to mind from recent years. Two years ago Tom Fine showed slides and home movies of Bob and Wilma at work, someone showed film of Layton/Mohr tracking sessions, and Dae Bennett and Phil Ramone did a great show on the tracking sessions for Tony's "Duets" records. (Tony was sick that day, and couldn't be there, which was a shame.) A panel session of producer/engineers paired long-timers Tony Visconti and Bob Power with a couple young successful newcomers - that old-timer versus hot-shot format gave a vivid picture of what has changed in recording, and what hasn't. Doug Sax's mastering session on the loudness wars some years back really framed the argument that was, up until then, somewhat nebulous. Most of the schedule is on the AES site, and the rest should be filled in next week.
WW
New Orthophonic High Fidelity
"...but you can fill up four long days from the couple hundred technical sessions they offer."
I can barely contain myself.
nt
New Orthophonic High Fidelity
I would hope that you, as a manufacturer, are a member of one or both organizations, and have voiced your concern to them, and that you learn from papers presented by researchers in applicable fields.In any case, isn't the "debate" among audiophiles regarding the audibility of polarity/phase reversal really about quantifying - measuring - its audibility, via a statistical analysis of results under controlled conditions, rather than through anecdotal stories or off-the-cuff "tests"?
I'm not sure why a manufacturer would pooh-pooh measurable science in favor of - what?
If you know of a professional organization which has better science presented in its publications, please tell me.
Edits: 08/04/13
"I would hope that you, as a manufacturer, are a member of one or both organizations, and have voiced your concern to them, and that you learn from papers presented by researchers in applicable fields."I suspect they wouldn't think too much of me, either, you know, as someone much more interested how something sounds than how it measures.
"In any case, isn't the "debate" among audiophiles regarding the audibility of polarity/phase reversal really about quantifying - measuring - its audibility, via a statistical analysis of results under controlled conditions, rather than through anecdotal stories or off-the-cuff "tests"?"
No, actually the debate is about the differences in sound. I.e., is it audible, to what degree, what is it about the sound that changes? Things of that nature.
"I'm not sure why a manufacturer would pooh-pooh measurable science in favor of - what?"
Uh, in favor of how it sounds. In case you can't tell yet, I'm not real big on measurements.
"If you know of a professional organization which has better science presented in its publications, please tell me."
To be honest, I'd be much more interested in the opinion of someone who is rather experimental and who also knows what he's listening to.
Edits: 08/04/13
"No, actually the debate is about the differences in sound. I.e., is it audible, to what degree, what is it about the sound that changes? Things of that nature."
Yes... Statistically verifiable and measurable differences, done under controlled conditions, partly to learn about what's going on, and partly to remove some of the mystery about what we can hear, how we hear, how that affects the design of audio products, rooms, systems, etc., etc.
Oh, like Monday morning quarterbacks. Sure, there's always a place for those measurement guys. By the way, what did those guys ever conclude about high end cables, you know, under controlled conditions? Besides, I thought the whole world loves a mystery. Why spoil it?
Besides, I thought the whole world loves a mystery. Why spoil it?
It depends what you’re doing, an “air of mystery” can be great for selling things and a real roadblock to advancing or improving the state of the art.
Tom, get back to me when AES or ASA or whoever comes up with a scientific explanation for high end cables, directionality of fuses and wire, coloring CDs, Schumann Frequency Generators, Crystals, Mpingo discs, demagnetizing CDs and LPs, ionizers, WA Quantum Chips, tiny bowl acoustic resonators, etc. If you tell me those organizations have better things to do I will totally understand. Wink, wink. Meanwhile sit back and enjoy the mystery.
Edits: 08/05/13
Actually, it's not the organizations which do the research, it's the members, who are typically manufacturers or university researchers.
The orgs are merely a means of promoting research and disseminating the results to the professional world for consideration. They also promote the establishment of standards.
The AES and ASA also invite comments which point out flaws in published technical papers, and those comments are also posted in subsequent issues of the journals. Given your "manufacturer" adversarial stance to these organizations, I'd expect to see numerous and credible critical comments from you with regard to the content in their journals. Please, can you cite any?
Meanwhile, how about you post some verifiable and repeatable results from your audio research and products?
:)
Why do folks always demand test results or some such thing from manufacturers? There is no such onus on manufacturers. Have you never heard of third party independent verification and validation? What do you think would happen if military weapon systems were not tested by a third party? Do you think the military should just accept whatever data or test results the contractor provides at face value? So, what's next, demands for controlled blind testing? Wink, wink
Edits: 08/05/13
"Why do folks always demand test results or some such thing from manufacturers?"
First of all, "folks" don't "always demand" test results or "some such thing".
But it does seem like a reasonable enough request, especially when the "science" behind a product isn't generally well-known. And, it helps to take the "snake oil" aspect out of the picture and give the product some credibility.
So, what exactly do you manufacture? Snake oil?
"But it does seem like a reasonable enough request, especially when the "science" behind a product isn't generally well-known. And, it helps to take the "snake oil" aspect out of the picture and give the product some credibility.So, what exactly do you manufacture? Snake oil?"
I prefer to characterize my products by saying the science behind them isn't generally well-known.
:-)
Edits: 08/06/13
"I prefer to characterize my products by saying the science behind them isn't generally well-known. "
Well that would make them perfect for an AES technical presentation then.
When a manufacturer develops something “new”, one of the best ways to get technical credibility is to do a presentation showing how it works to other engineering types.
Assuming one can explain how it works (a requirement to engineer something) , it is one of the best ways to rise above the “kenoki foot pad” level of credibility / marketing.
The Kenoki foot pad was an example of a product which had a faithful following of believers who were disappointed when it was revealed that the “impurities” that leached out of your body, were actually contained within the pad and in reality it did nothing that was claimed.
The faithful were simply duped by what they wanted to believe the pads did.
A plausible sounding explanation and result that requires belief, is not the same as something based on a demonstrable scientific principal.
In other words, things based on scientific reality generally withstand the examination when exposed to the light of day, while phonies recoil from the same scrutiny
Nothing much grows in the dark, Tom
{Smile}
The Mind has No Firewall~ U.S. Army War College.
Hey, Tom, anyone is free to try my products, which number twenty something, plus there is a 30 day guarantee fir all of them. I don't even mind if they emply controlled blind tests ir any type if tests they desire. I suspect orgs such as AES actually have no interest in pursuing new technologies, otherwise they would almost certainly have contacted me by now. Ditto ASA. Of course, it's possible the organization, or rather the individuals in the organization, might claim that they never heard of me or my products. And that response would certainly be understandable. Furthermore, I suspect once you raise the specter of quantum mechanics and things that don't operate directly on the audio signal, so-called audio experts are a little leery about getting involved, it's just not good for business, if you see what I mean. Business as usual, I should say.
~!
The Mind has No Firewall~ U.S. Army War College.
When I first met John Curl in Montreux many moons ago, and he was going to assist in teaching me some things, the first thing he asked was "Do you know your differential equations?". At that moment, I knew I was in over my head, 'cause I didn't even know what a differential equation was.
:)
I taught John Curl how the Intelligent Chip works. You know, quantum mechanics. I tried to explain it to Jack Bybee, but he admitted his quantum mechanics was about 50 years out of date.
I am not sure you have the right image of what they do.
They do not seek out new things to review or act as a “police” agency, it is a place where the people with the discoveries can present them and explain them in hopes that they will be recognized as a breakthrough or as a technical explanation of how they work.
The audiences are the most technical people in the industry so even presenting there says something.
Also, since there are physicists who are into audio and even work for audio companies, there would be little risk presenting things using quantum mechanics as long as the explanation was consistent with what is known about that.
This is not the place to BS people however or to present something which cannot be supported based on engineering / physics .
If you can present a test where people that didn’t know what they were hearing could hear a difference between X and Y that would also be the basis to present a less tangible explanation.
Fwiw, I have demonstrated several new loudspeaker transducers and technologies live at both AES and ASA and found them to be very receptive to “new things” and an attentive curious audience.
I am an invited participant on a panel discussion on intelligibility for the next one in NY if you happen to present, I’ll look you up.
If you want to step into the next level of credibility, this would be a great thing to consider.
10-4 Tom.
I remember being at an AES convention in L.A. back in the 70s, when Dan Dugan presented a paper on his automatic muting feature for live sound mixers for conference PA systems. And then there was Cecil Cable who described his "foot-fall" device to make repeatable foot fall noise measurements for building construction spec verification. Oh, and someone who showed that tire/road noise was a greater sound source than engine noise with regard to vehicle environmental noise. And let's not forget that guy Matti Otala with his paper about crossover notch distortion in amplifiers. 'Course, then there's also the team of Stanley Lipshitz and John Vanderkooy.
And, that Richard guy. What's his last name again? Oh yeah, Heyser. And listening to John Hilliard go on and on about loudspeaker design, well, ...
What a bunch of closed-minded people!! ;) I can see why Geoffkait wouldn't want to hang out with any of them.
:)
...cables do not, and never will, "sound different". He exercised his ignorance extensively at the AES 91st. Just sayin'.
P.A.
Dick Heyser is one of my audio “hero’s”, I only met him once and didn’t say much (not wanting to put my foot in my mouth) but came away felling lucky to have been among audio giants that evening.
I have had a TEF machines for about 25 years now and between it and Dick’s writing, I could never have designed these loudspeakers without him.
https://www.dropbox.com/sh/nmmmdtum82lyig9/QnEaYWlnDE
As Don Davis once said, we stand on the shoulders of the giants who came before us.
Armed with the truth, on need not fear the outcome of technical scrutiny.
Hey Tom, that's very cool that you had a chance to talk with Richard Heyser. People like he and John Hilliard (who I had lunch with, along with Cecil Cable and Ron Streicher), Don Keele, Harry Olson, and others are like rock stars in the audio world.
:)
I'm pretty sure I have the exactly the right image for what they do. If you can access the archives of the Journal of Acoustical Society of American there was a kind of tongue in cheek article on Machina Dynamica, my co., around six years ago. I am pretty sure that article illustrates my point perfectly. Old and in the way I think better characterizes that sort of mind set, you know, rather that open-minded and curious, two requirements for real scientists the last time I looked. Why would I put myself in the position of beng peer reviewed by an organization that is no more tolerant, open-minded, or curious than say Hydrogen Audio or DIY Audio?
Edits: 08/07/13 08/07/13
"If you can access the archives of the Journal of Acoustical Society of American there was a kind of tongue in cheek article on Machina Dynamica, my co., around six years ago. I am pretty sure that article illustrates my point perfectly. "
No doubt, you wrote a response to the article, and they published it. Both the AES and ASA are in the habit of publishing replies from the author of an article or from the subject person/company of an article. What did you write to them as a response?
I did not respond to the article, actually. What could I possibly say? That's kind of the whole point.
"I did not respond to the article, actually. What could I possibly say?"You could have refuted untrue statements, and clarified the rationale of your science. It was a perfect opportunity to speak to the professional community and earn credibility.
Geoff, really, if you don't have a leg to stand on, scientifically, just say so. But don't go around bad-mouthing other people who clearly know what they're doing - it makes you look silly and petty.
Edits: 08/07/13
I think you probably need to read the article before you go accusing me of anything. Your attitude is well just as silly as AES, if you don't mind my saying so too much. You do realize dismissive attitudes are not very scientific, don't you?
Edits: 08/07/13
No, I haven't read the article. What article? Can you point to it? I'm not going to sit here are try to find "an article" from "about six years ago" when you've not even cited a title or an author. When you do, I'll look into it.
For now, I'll reply to this:
"Your attitude is well just as silly as AES, if you don't mind my saying so too much. You do realize dismissive attitudes are not very scientific, don't you? "
Silly as AES? Dismissive attitudes? Who's being dismissive and not very scientific here, Geoff? I'm aware that you've been laughed off at least one other audio forum. Here's your chance to step up and set the scientific record straight with regard to yourself and professional associations. Simply scoffing at others isn't doing you any good.
:)
As it turns out the letter that appeared in the Journal of Acoustical Society of America can only be viewed by logging into the ASA archive. Will you take my word for it? Being snide and dismissive is not being scientific, even though you apparently think so.
give me some data such as author, title, volume no., issue no.
Klaus
"A short history of bad acoustics"
J. Acoust. Soc. Am. 120, 1807 (2006); http://dx.doi.org/10.1121/1.2336746 (9 pages)
For access to fully linked references, you need to log in.
Here's the part of that article where Machina Dynamica is mentioned:
#########################################################################
B. Snake oil for the ears
The fact that the human auditory system is connected to the human brain makes it a marvelous subject for study, but it also means that we are capable of being fooled about what we are listening to. This, among other factors, has made objective assessment of subjective listening experiences very difficult, and easily swayed by suggestion, a fact that is exploited by many purveyors of devices that purport to improve sound.
Architectural acoustics was prey to a form of this delusion as recorded by Sabine (stretched wires in churches, court rooms, theatres).
Many readers will know of the long debate over the importance of Stradivari’s varnish to the sound of his violins. Consider, then, the claims made by luthier Dieter Ennemoser for his C37 varnish.
Once the sound has left the loudspeaker it still needs to survive transmission through the room.
"Brilliant Pebbles is a unique room & system tuning device for audio systems and satellite TV. Original Large Brilliant Pebbles is a 3-inch clear glass bottle containing various minerals/stones. A number of highly-specialized, proprietary techniques are used for preparation/assembly. Brilliant Pebbles acts as both a vibration “node damper” and EMI/RFI absorber via various atomic mechanisms in the crystal structures. On the floor in room corners, Large Brilliant Pebbles reduces comb filter effects caused by very high sound pressure levels that occur in the corners when music is playing. Large Brilliant Pebbles is also effective on tube and solid state amps, on speaker cabinets, on armboards of turntables and on tube traps and Room Lenses."
The doyen of this field is Peter Belt, whose products have a small but devoted band of followers who seem to be convinced beyond doubt that their listening experience has been enhanced by the use of his products. And how could they not, after all. If the actual effects of these foil strips, jars of stones and varnish might seem negligible the prices charged for them are certainly not; readers are invited to guess what they might be before investigating for themselves. Of course, the actual value of any such device can be separated from the psychological effect of its presence and price on the listener by careful double-blind testing. Sadly this is strongly resisted by a significant proportion of the audiophile community. Until it becomes commonplace it will be hard for those who seek to improve Hi-Fi systems by legitimate means to distinguish themselves from those who just sell false hope. As a last psychosociological note it is worth pointing out that such devices are given short shrift in the world of professional audio systems, where the audience neither knows nor cares what has been done to the equipment, and is therefore immunized to the power of suggestion.
#########################################################################
What could you possibly have said in a letter to the editor? Maybe you could have provided some solid evidence that the devices work as claimed? Maybe you could have provided some solid scientific/technical explanation about how they work?
Klaus
"Of course, the actual value of any such device can be separated from the psychological effect of its presence and price on the listener by careful double-blind testing."
You are falsely conflating "value" with "physical effect". Value is an economic concept, not a physical one. As such, a product has value according to the subjective judgement of a purchaser. There is no objective standard of value, as the value of an object varies as a function of time, place and person.
If someone is happy with their purchase of an audiophile doodad, that product has value to them. (You may think they are a fool and they may think you are a nerd. Such opinions are of no value or physical effect.)
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
Good question. Most likely, considering the audience, the less I say the better. The mainstream audio industry was not ready for the intelligent chip or crystals 8 years ago. I hate to judge things too quickly but I suspect it still isn't. As you know I did provide solid scientific explanations for how they worked - eight years ago!
“As you know I did provide solid scientific explanations for how they worked - eight years ago!”
As you know I had contacted Altewischer himself, and he and his colleagues were laughing back then and must still be laughing.
Altewischer, Nature, 2002: “Experimental realization of quantum entanglement is relatively easy for photons; a starting photon can spontaneously split into a pair of entangled photons inside a nonlinear crystal.”
This using a 240 mW krypton-ion laser beam of 406.7 nm wavelength, which isn’t exactly the wavelength of a CD laser! And a photon being split in two isn't exactly the same as two photons encountering each other on a random basis!
A solid scientific explanation? In your book maybe, not in mine. Get your explanation published in a peer-reviewed physics journal, or in Nature, or in Science, then, and only then you may call it solid.
So I'd say, no, mainstream audio industry professionals are no more ready today for such gadgets than they were 10 years ago, and for good reasons.
Klaus
Nice to see nothing has changed. No surprise here.Of course the important thing is if milk squirted out of Altewischer's nose when he laughed.
Mainstream professionals? Now there's a group in need of a serious makeover. :-)
"Just what makes that little old ant / Think he'll move that rubber tree plant / Anyone knows an ant, can't / Move a rubber tree plant / But he's got high hopes..."
Edits: 09/13/13
"Mainstream professionals? Now there's a group in need of a serious makeover. :-)"With or without the smiley, you've dismissed the scientific community in several of your posts. Yet, you have completely failed to offer even a single shred of evidence to justify doing so.
What exactly is it that disqualifies people like Hilliard, Lansing, Heyser, Toole, Small, Thiele, Linkwitz, Curl, Beranek, Otala, and many others from earning your respect for their work?
For some inexplicable reason, you cling to some notion that the scientific community is misguided, yet you offer no coherent explanation as to why, nor do you offer any evidence that your so-called "solutions" do anything other than to affect the psychological disposition of the buyer and to line your wallet with money from unsuspecting and gullible customers. You should be ashamed of yourself.
Edits: 09/13/13 09/13/13
You forgot the pseudo skeptics' favorite admonition::"Extraordinary claims require extraordinary evidence."
The inmates are restless.
Smiley face
Edits: 09/13/13
"You forgot the pseudo skeptics' favorite admonition::"
Actually, I didn't forget anything, Geoff Kait of Machina Dynamica.com, except to mention Geoff Kait and Machina Dynamica.com.
I wrote exactly what I intended to write.
And of all the opportunities you've had to state your case for your machina dynamica "products", Mr. Geoff Kait, and dismissing the audio & acoustical professions, you still fail to offer even one coherent thought which backs up any of your assertions.
I'd be happy to reply to anything you say of substance. Until then, Geoff Kait of Machina Dynamica, you have no, none, zero, credibility, and, as I wrote in a previous post, you should be ashamed.
I couldn't possibly respond with less substance than that. Mainstream professionals everywhere must be getting a little nervous.Have you considered taking a nice cold shower?
Edits: 09/13/13
I guess you figure that would make you equals.
Your oh-so snarky comeback is now awaited. 1, 2, 3, ...
How could I possibly out snark the old snarkmeister?
You're doing it again - no facts, nothing substantive, no meaningful reply. Have you got an "article" (now a "letter") title, author, issue number, or ANYTHING to go on? (If I were a betting man, I'd bet that you have the entire text practically at your fingertips.)And, no, I'm not going to take your word for it. You've already called the AES "silly", you've changed your characterization of the ASA piece from "article" to "letter", you've called me "dismissive" when you've done the same to two of the top audio and acoustical professional associations without anything to back up your assertion, you've called me "snide" when all I've done is ask for something - anything - that means anything. But you continue to spout nothing but vapid platitudes and meaningless assertions.
Why on Earth would anyone take your word for it?!
Edits: 08/14/13
"I suspect orgs such as AES actually have no interest in pursuing new technologies, otherwise they would almost certainly have contacted me by now."
Oh yea, that's bound to be it.
Perhaps if you were to join and offer to present a paper?
Just a thought...
Rick
That's so funny. Apparently I have more experience with both AES and ASA than either of you guys. I'll go out on a limb and say that both organizations are simply old and in the way of real progress, preferring to rest on their laurels.
Charles Wood in 1962 developed a test to see if absolute phase is audible.
He clipped the top of the waveform and after a listening session he inverted it 180 degrees and listened again.
Results were a noticeable change in timber between the two sessions.
Here is a good article about it.
This something that I found a long time ago from Clark:
Clarkjohnsen acoustic polarity
What to listen for:
1) Better dynamics - "leading edge" of notes more defined. This is both when music is played soft or loud. But it also helps separate out softer sounds when other instruments are being played loud. This not a huge night and day thinng but is readily observable.
2) Better sound stage proportions - wider, deeper, and more forward.
3) Better focus of individual images - particularly singers, will come forward and be more separate from the "mix" when AP is right. When AP is wrong the soundstage becomes more two-dimensional and singers move back in amongst the other instruments.
4) Sibilance and distortion of higher frequencies. More sibilance on voices is usually sure test (for that microphone). Splashing and edgy cymbals another for incorrect AP. Violins are a good test - they become steely, edgy, and annoying whem AP wrong, and more silky, balanced and dynamic when AP right.
5) Bass is more dynamic, punchy, and detailed when AP correct, looser with a bloom when wrong.
6) The is more of what can best be describe as a "haze", a light fog making it harder to differentiate what is going on when AP wrong.
7) Another good test is sitting off centre - when AP is correct you will find image from the centre and far speaker "stay put" somewhat better. With wrong AP the images will tend to follow the listener more.
8) Having well designed coherent speakers with good impulse response makes it easier to differentiate all of the above - but is not essential.
Regards,
Todd
I am familiar with Clark Johnsen's work, but I have not read Wood's original study. One thing that concerns me with Wood's results is that second harmonic distortion in the playback chain (e.g. speaker) could invalidate a conclusion that human ears can hear polarity reversals, as the amplitude spectrum would differ for the two polarities of Wood's asymmetrically clipped waveform. Perhaps Wood controlled for the possibility of speaker distortion, but if so, I've not seen this discussed.
In addition to the ability to hear the effects of polarity reversal, there is the question of whether recordings sound better (e.g. more natural) when presented with correct polarity vs. reversed. There are some logical issues here, especially given that some musical instruments radiate to the audience with differing polarity according to their orientation. It would also be interesting to see if (a) one individual is consistent in his selection of preferred polarity of a particular recording and (b) multiple individuals agree as to the correct polarity when listening to the same recording on the same system. There are test devices that are designed to aid in setting up correct polarity of public address systems and these can be adapted as an tool for recording polarity experiments.
From a practical point of view, I have a polarity reversal button in my DAC and can swap it whenever I want. Along with the volume control and the location of my listening chair I use polarity to fine tune a playback so that it sounds "the way I like it", for whatever that's worth. Your mileage may vary. :-)
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
The original Wood experiment of 1957 used headphones... on cats' ears! It was cited in a 1962 article by Craig and Jeffress writing in JASA, who replicated the results on humans but without a truncated waveform.
P.A.
Using headphones could be open to the same criticism of second harmonic distortion.One test that would be immune to this kind of criticism would be if a bipolar speaker were used and it were constructed with complete symmetry and located symmetrically in the listening room. (I don't know if any commercial bipolar speakers meet this test, as the ones that I am familiar with have a clear "front" and "back".) With such a speaker one could reverse polarity by a 180 degree rotation of the speaker.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
Edits: 08/03/13
Question, In a typical rock recording with maybe 15 to 25 microphones or more with all instruments having there own mike and overdubs done at different studios what does correct absolute phase really mean. Reversing absolute phase may make a recording sound different but I doubt it has anything to do with correct absolute polarity of the recording
Alan
The situation is complex if there is a forest of microphones, but if they are far enough apart and close enough to the individual instruments then the multiple microphones won't affect the polarity, assuming that the microphones, preamplifiers, and cabling is different. (There are two standards for pin-out on balanced XLR cabling, which can lead to confusion if different brands, e.g. different nationalities, are used.) In addition, figure 8 microphones are sometimes used and they are velocity sensitive, which means that the polarity on one side of the microphone is reversed. Some recordings have one microphone shared by two singers and if this is done with a figure 8 microphone the singers will be in opposite polarity.
Absolute polarity is most easily heard on a single microphone monaural recording played back on a single driver speaker system. Here all one needs is an AM table radio. Many multi-way speaker systems have their drivers wired in opposite polarity and they scramble phase, making it more difficult to hear the effect. As far as I know, none of the people who have done research on absolute polarity have done "live" vs. "recorded" demonstrations or showed that the correct polarity sounds better (rather than merely different as you suggested).
I have attended a jazz concert where the polarity of the PA system used on the singer was wrong. At the set break I went up to one of the band members and remarked that the polarity was wrong. He believed me, because he was getting bad sound and didn't know why. We reversed the wiring on both speakers and the second set sounded much better. There is test equipment that can be used to calibrate correct acoustic polarity. Getting acoustic polarity correct is essential in PA sound reinforcement situations.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
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