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In Reply to: RE: You missed the point... posted by Steve O on November 12, 2015 at 17:48:08
I was commenting on statements like this one:
Perhaps next time you might quote the text to which you are responding.
Good measurements do not preclude good sound.
Certainly not. Nor do they have any correlation to good sound. Usually the converse is true.
While it's probably reasonably true today that the correlation between good meas performance and good sound is mildly positive
If you refer to THD measurements, I find the converse to be true. Those with "heroic" distortion metrics (via boatloads of "corrective feedback") usually sound unnaturally lean and flat dimensionally.
Follow Ups:
Setting aside good measured performance, does poorly-measuring equipment sound good despite that or because of it? Is there some quintessence of music that can only be conveyed by less-than-stellar objective performance or does that poor performance add something that makes it sound preferable?
Steve O thinks that there is a stronger correlation between good reviews and poor measured performance than between good reviews and good measured performance. And, in regard to THD, you agreed with him.
Not wishing to put words in anyone's mouth, but the point then is that if well-measuring equipment can sound good it is more likely that poorly measuring equipment is preferred for what is adds rather than what well-measuring equipment cannot do. So, in those terms, measurements do matter.
"it is more likely that poorly measuring equipment is preferred for what is adds rather than what well-measuring equipment cannot do. So, in those terms, measurements do matter."
This is not the case. What is defined as "poor" measuring is that it has a somewhat high THD or IMD compared to "state of the art" but if the harmonics are in the human perception "blind spot" then it is acutally the other way around in terms of which product has good measurements. Those that measure poorly are high in low order harmonics relative to high order harmonics...this is a pattern similar to one observed in nature. Those that measure well have disrupted this pattern because they have pursued the ENGINEERING goal of low absolute distortion rather than the SONIC goal of low to no higher order distortion.
.. it shouldn't become a hall-pass for designers to not do a good job.
You can't help getting high 2HD with something like a single-ended triode so how much care/knowledge does the designer really need? But, you are correct about it all depending what the goals are.
I do wonder whether high levels of consonant distortion are subjectively better subjectively because they mask-out dissonant distortions or because they just sound nicer on their own. But, in the great scheme of things, it probably doesn't matter too much.
Regards
13doW
". it shouldn't become a hall-pass for designers to not do a good job." If it measures good and sounds bad does the designer get a pass for producing excrement with good specs?
Define not doing a good job, please.
"ou can't help getting high 2HD with something like a single-ended triode so how much care/knowledge does the designer really need?"
Very much actually because the goal is to keep the distortion low order and prevent the rise in high order harmonics...this means a lot of care in the design of each stage of the amplifier and careful balancing of operating points, passive parts choice and most importantly using a great transformer (at least the best that is affordable for a given design price point). It is a lot harder than making a mediocre design and cleaning it up with copious amounts of negative feedback.
" I do wonder whether high levels of consonant distortion"
Let me be clear, there is no such thing as "consonant" distortion...all distortion degrades fidelity but some does much more damage at much lower levels than others. Read the articles in Stereophile by Keith Howard where he added different distortion patterns to different music selections. He found no added distortion was the best (no surprise) but he also found that some patterns were far worse sounding than others. The monotonic pattern that was championed by Hiraga was found to be the least offensive of the distortion patterns he tried. This is the same pattern that Cheever concludes should be the least audible and that Geddes data also corroborates. Now, ideally we have a linear amplification device that gives no additional harmonics or IM distortion but since all our devices are "bent" then that ain't going to happen.
JA often calls triodes without feedback "bent" but the truth is that the triode is the least "bent" of all amplification devices, with the BJT and the Pentode being the most "bent". That is the true reality.
I think the white paper from Nelson Pass regarding negative feedback is interesting and illustrates quite well what is wrong under the surface. You don't really get rid of distortion but you seem to just push it around...Crowhurst said that the result is a kind of signal modulated "noise" floor that will mask low level resolution and damage dynamics.
And yet , regardless of what you , me and others think, many more like class-d sound over SET sound, oops, so much for the theories.
Since it's all wrong, whats next ....?
Go Rossi ......
Edits: 11/13/15 11/13/15
What I find is this:
Tubes and SS...
"Vocals are run through passive Renkus Heinz mono PA with Cary Audio Hi-Fi tube amplifier...
The other end is a two channel hi-fi playback system with Revel Saloon II speakers coupled with Levinson solid state, bi- amps. Rogue Audio tube pre - amp, Benchmark DAC , Esoteric transport and Sony Media Server. "
"I've owned numerous equipments..."
Start about 9:55. And none of it class D. :)
There is a room with Wilson Alexandrias in it. So, what does Dave Wilson use for making his recordings?
Answer here .
How about when Wilson shows their product at shows? Find out here .
Dave definetly know how (i have a few ) to make recordings , I'm also a big fan of prof Johnson reference recordings ....
!
Go Rossi ......
Edits: 11/14/15
if your point was simply the need for room treatments (to me an obvious requirement for any high performance system), then I heartily agree.
How many audiophiles spend big $$$ on the hardware and not the room?
I will bet Hypex has sold more ncore amps in the last 2 years than all the SET manufacturers combined....One would think that if they were all that, more people would be rushing to buy one...
No doubt SET offers something some people like, just as class d does. Trying to build a theory for their "superiority" is like trying to "prove" Thai food is superior to Italian....
It's also not necessary for enjoyment of one's hobby. I fail to understand the need to find some sort of rationale as a basis for the ownership of a certain type of equipment, or the need to belittle what others enjoy. I suppose there will always be those who need to feel superior, small and insignificant as it may be....
try it! you know you want to!
many more like class-d sound over SET sound
I have yet to meet someone who actually stuck with Class D. It definitely sounds different and for many that is good enough.
I know a lot of guys who tried it and tried to live with it though and all gave up on it.
I haven't given up yet, but if it takes 50K to hear what class-D sounds like,i will have to take Kurby's word for it..Have to sully myself with the usual bad SS stuff ... :)
Regards ..
Go Rossi ......
Edits: 11/13/15
For my own part, I think class D is the rising star in audio amplifier technology, but so far hasn't brought home the bacon. But that might be different tomorrow- the technology is still in a steep portion of the price/performance curve.
If you need $50K to understand what its about- well, traditional technologies need nothing of the sort to demonstrate what they do in spades. I think I'll wait too...
I think class D is the rising star in audio amplifier technology...
when implemented as a "Power DAC" or using other means (Devialet's current dumper/Stasis) to eliminate the prodigious amount of HF noise.
"Good measurements do not preclude good sound.
Certainly not. Nor do they have any correlation to good sound. Usually the converse is true."
If the converse is true, there is a correlation, a negative correlation, yes?
"If you refer to THD measurements, I find the converse to be true. Those with "heroic" distortion metrics (via boatloads of "corrective feedback") usually sound unnaturally lean and flat dimensionally. "
Not necessarily THD alone since there are other measures of linearity and maybe even good sound. Also not clear what you mean by "heroic". FWIW, an amp with low THD and other good traditional meas ( thru use of corrective feed forward ) is also getting tairly decent listening reviews too...the new Benchmark amp. I want a pair!
If the converse is true, there is a correlation, a negative correlation, yes?
Yes.
Not necessarily THD alone since there are other measures of linearity and maybe even good sound.
To wit?
To wit!: IMD, SID, smoothly decending levels of high order distortion products (there's name for this condition but it escapes me at the moment), basic stability, rapid overload recovery and so on. Optimizing any one or two parameters is probably insufficient so it's really an exercise of judicious balance. Much of this stuff was known and effectively dealt with in the middle of the previous century by a few designers.
Geddes found that IMD also has no correlation (actually slightly negative but statistically insignificant at the 95% confidence).
An interesting paper by Geddes. Since you've cited Geddes on a couple of occasions here, I assume you're familiar with his paper.
While I'm not qualified to directly butt heads with Mr. Geddes, what he describes in his paper raises a number of questions.
1. The testing methodology employed a 15 second excerpt from ALW's "Phantom of the Opera" ripped from the redbook CD and converted to a .wav file. This was considered "the reference". Is 16/44.1 sufficiently resolving considering the potential subtleties involved? Is the music selection sufficiently revealing? Is a 15 sec sample of sufficient duration?
2. Twenty one different stimuli (distortions) were mathematically simulated (calculated). The exact nature of the distortions is unclear as is the correlation of them to real life distortion generating devices. The calculated distortions were then used to multiply the input reference wav file to produce the test sample or signal. All stimuli were digitally adapted and presented to the subjects via computer...as 16/44.1 wav files. Is a mathematically generated distortion a valid means of simulating the performance of a physical device? Has this methodology been validated by Geddes or independently by others?
3. Subjects rate the test signals as better or worse than the reference. Doesn't this predispose the results towards "preference" instead of "accuracy"?
4. Geddes finds a weak negative correlation between THD and IMD and preference but essentially dismisses this finding based on statistics and pursues it no further. He also finds a moderate positive correlation between the proposed Gedlee measure (Gm) and preference. He then chooses to improve the statistics of Gm by throwing out three unsupportive stimuli. Is this appropriate?
5. The paper is 12yo. Has there been any independent validation of the methodology or verification of the results? Have there been any additional developments or refinements of the Gm concept since 2003? Is any independent mfgr using Gm in place of or as a supplement to more traditional measures? A quick web search turned up nothing but not being a member of AES may be a limiting factor.
Overall, I found Geddes' findings and proposal to be interesting. But really isn't this just one relatively old data point and another dead end in the search for a means of correlating objective device performance with subjective preference or "goodness" using one or two measures?
1) I would assume it was chosen specifically it's revealing nature and i think 16/44 is sufficient.
2) There is another paper that discusses the distortion in more detail (it is a theory paper).
3) No, preference is a better way IMO as it takes off some of the pressure of "do I hear" vs. "what do I hear".
4) I think the findings of THD and IMD mirror what a lot of audiophiles out there complain about. I do not think that what Geddes does with his own metric is all that valid (one data point maybe if it fails a Q test but not three). His metric suggests he is on the right track but the fact of a weak correlation means there is something missing from his model to make it more complete. Maybe Cheever's model would fair better? Apparently, Shorter's simpler model was not that effective either or maybe more would use it.
5) I found a more recent pub from a Swedish (or Danish) group that reached similar, but more difficult to understand, results
Based on the synthesis of all recent research I have read I reached the conclusions that I posted some time ago on the amp/preamp forum.
http://www.audioasylum.com/forums/amp/messages/20/208108.html
I stand by my analysis until such time that I hear something or see research that falsifies what I wrote.
I posted a link where you can take the test yourself ,
Geddes findings and research is valid, what is not valid is how much of it actually correlates to us in actual use , when one hears their favorite song vs non familiar music , our sensory system will and usually does change gears...Short of directly taking and using amplifiers with the distortion characteristics suggested by Geddes research with golden ear audiophiles , what are we really proving....
Regards
Go Rossi ......
Edits: 11/14/15
Geddes found that IMD also has no correlation (actually slightly negative but statistically insignificant at the 95% confidence)- Morricab
Go Rossi ......
nt
try it! you know you want to!
Yep, that's the one
That wasn't difficult, was it?
Much of this stuff was known and effectively dealt with in the middle of the previous century by a few designers.
Then such got lost when SS first arrived and the arms race for "better" metrics and worse sound was prevalent. :)
"Then such got lost when SS first arrived and the arms race for "better" metrics and worse sound was prevalent. :)"
Seems that way although I don't believe "worse sound" was an actual design goal back then. I'd guess that the degraded sound was the result of the pursuit of unbalanced objectives with advertisable power and distortion specs taking precedence at a time when SS technology was not well developed. I have to believe the better designers knew what was going on but weren't in a position to resist.
The problem is the outcome of the techniques used to lower distortion, namely push/pull and negative feedback. The outcome gives the desired ENGINEERING solution of low distortion but doesn't achieve the SONIC soluton of having a proper harmonic content for good sound.
I'd guess that the degraded sound was the result of the pursuit of unbalanced objectives
Absolutely and to the point of this thread - chasing metrics that fail to correlate with qualitative aspects of the listening experience.
Which continues today with some designers.
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