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In Reply to: RE: Just a music lover posted by E-Stat on June 14, 2024 at 12:37:24
Feanor himself will tell you that I'm not like him an any significant way. So do you totally ignore graphs? If so, I think that kind of isolates you to your own little corner of the audio universe, along with a few other true believers. ;-)
And BTW, which is it? Negative feedback is OK, or noise and distortion are OK? Maybe a little of both for you? LIKE FOR MOST OF US? Remember, I listen to most Dolby Atmos recordings in LOSSY 24/48. ;-)
Follow Ups:
Feanor himself will tell you that I'm not like him an any significant way.
Ok, so your shared enthusiasm for the value of SINAD is not significant.
So do you totally ignore graphs?
Only the ones that don't correlate to what we hear.
I do, however, use measured graphs to fine tune speaker placement and EQ for the HT. Here's upstairs which took some work along with a small forest of bass traps to achieve.
Negative feedback is OK, or noise and distortion are OK?
Why not quote something I posted and frame a question based upon it?
"Ok, so your shared enthusiasm for the value of SINAD is not significant."
Why not quote something I posted and frame a question based upon it?
[I] ignore the [graphs] that don't correlate to whatweI hear.
There! Fixed it for you, Mr. Self-Appointed Golden Ears.
Why not quote something I posted and frame a question based upon it?Question unnecessary.
Calls to mind this . Like Feanor, you're also not in the Geddes camp where correlation is the objective.
Edits: 06/14/24
"Calls to mind"? Not to most intelligent people.
Sometimes, the correlation exists, but you simply deny that it does.
Geddes papers show a correlation does not exist.
I brought up the question of measurements in general, and you're trying to confine what I said to THD only.
from the Geddes interview:
"That's the problem with THD, it just does not show what we need to know."
I learned that lesson as a teenager.
I'm convinced Chris didn't follow and thus doesn't understand my "calls to mind this" embedded link where another inmate asks why he makes snide and scornful conclusions. Seems he rarely follows embedded links I provide and later asks question answered by them.
His reply is all the more ironic. ;)
. . . you act as if I'm totally pushing THD as the be all and end all - which I NEVER have done. Check this thread. I just say that, in my experience, measurements (in general - not just THD) DO usually correlate with listening experience. Even YOU have admitted that when you say you use frequency response measurements to improve the bass response in your room.
What do frequency response measurements (linear distortion) have to do with THD (non-linear distortion)? What studies have you done to demonstrate that you can correlate your preferences with THD level? I guess the answer there would be none, right? It's just your gut feeling that you would prefer a low distortion amplifier over a higher distortion one.
. . . I quoted?
If you bothered to read the papers, he explains what he is on about and that he developed a metric to process distortion in a more meaningful way than THD and IMD. His metric takes the THD and IMD data and establishes a much better correlation with what the listeners reported than just plotting that versus THD or IMD.
So, what he said in the interview doesn't contradict the papers.
I'll quote the relevant part once again:I have also never believed that all that matters is "how it sounds," because this is such an unstable and personal opinion. Sound quality opinions can and will differ from person to person, system to system and most importantly even within the same person on different days (as I said before, I have personally witnessed this in well regarded "reviewers"). Personal preferences have such a low stability as to be an almost completely pointless thing to stake a claim to.That does not sound to me like he takes "what listeners reported" very seriously, metric or no metric. Contrary to your assertion, what he said in the interview DOES contradict your summary of the paper(s). How recent was his paper? Maybe he changed his mind over time.
Read the papers and slide presentation and answer the questions for yourself.
He is talking about an individual response. Taken in aggregate you will build a statistical preference for most listeners (assuming you have a good correlation to the measured data) for particular types of distortion vs. other types.
Geddes papers (if you don't read them then we have nothing more to discuss) indicate that THD and IMD had no correlation (even a slightly negative slope) to the distorted sounds they were subjecting listeners to. When he applied his metric, which takes into account some kind of weighting for harmonic content, he got a much stronger and positive correlation between preference and his metric.
I scanned through the two AES papers and the conclusion is convincing that THD and IMD doesn't match the subjective scoring of their test group whereas their Gm metric (bad choice of symbol as Gm means something else to a lot of people) does correlate much better. There is much to pick over - in the first part they don't quantify masking. Yes it is a psychoacoustic thing but how much effect does it have and why choose a cos^2 weighting factor? I also question one of their precepts that distortion will be more apparent at low signal levels than high signal levels - that needs some explaining as distortion grows quicker than the signal level that causes it (i.e. if a signal increases by 1dB any second harmonic will grow by 2db, third harmonic by 3dB etc).We aren't told what the 21 transfer functions are nor their correspondance to trial number. We do know one/some/many have severe discontinuities - are those really relevant for high-end audio? And they remove 6 of those transfer functions at the end because they don't fit the scatter plot so well (at least they were open enough to admit this as data manipulation is often a big problem in academic papers).
But, the big unanswered question is whether a low distortion system is somehow worse? We don't know because they don't detail the transfer functions! We can probably conclude that many non-linearities are not that audible, or audible at all, but we can't conclude that low distortion devices are somehow subjectively inferior. So it is a bit of a shield for audiophiles to stand behind and an excuse for high-end audio designers to not work too hard but not the full story.
Edits: 06/20/24
Indeed! Rush rules!
Cheever added an SPL factor into his model because there is also a change in the ear's own generated harmonics. It also then would depend on the sensitivity of the speaker and how much distortion/power at a given SPL...
So, a high sensitivity speaker that only needs mW to a couple of watts will be an easy, low harmonic dominated (which are basically masked) distortion pattern that will sound clean.
Once you get beyond a certain SPL it will really depend on how rapidly the devices distortion, particularly the high order harmonic distorion rises and how that still compares to the ear/brain masking...complicated but can go a long way to explaining a lot of the subjective varaiabilty observed.
"But, the big unanswered question is whether a low distortion system is somehow worse? We don't know because they don't detail the transfer functions! "
It is not low distortion per se, it is the fact that there are high order harmonics without lower order harmonics to provide masking. The audibility seems to be down to very low levels. Achieving this with negative feedback has it's issues with regard to artificial noise floor (read Crowhurst and Pass white paper) and IMD that gets generated. Just seeing absent harmonics in a static test does at all tell the whole story.
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