Asymmetrical waveforms !

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Nick
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#106 Re: Asymmetrical waveforms !

Post by Nick »

steve s wrote: Sat Jun 04, 2022 12:21 am
Nick wrote: Fri Jun 03, 2022 10:46 pm After all if it measured like that and still didn't sound that good, its clear that we cant trust measurements, or at least there is no correlation between measurements and sound

I think many of us would be in full agreement with that nick, ( hopefully I've quoted in the right context)

I suppose the question on my mind is why, despite the 'perfect' measurements
Maybe you misunderstood my point. I was questioning that the measurements were that good in the first place. If you read any good book on amps its clear that part of the problem is working out how to make measurements that tell us useful things, but marketing just prefers a numbers war. To an engineer measurements should be a measure of whats wrong with something, to marketing they become a way of claiming there is nothing wrong.

Another pet phrase, If you can't measure what you value, you end up valuing what you can measure.
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Nick
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#107 Re: Asymmetrical waveforms !

Post by Nick »

I think it's like the issues F1 cars have. Despite the "perfect" measurements in their static testing and wind tunnel, the car on the track can do something completely different under dynamic conditions. Witness Mercedes and their porpoising issues.
But where it differs, is that I am sure that the engineers didn't throw up their hands and declare that they would sell the wind tunnel and shut down the CFD. They would have been working to understand the lack of correlation between reality and the measurements/simulations to make them more useful.
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#108 Re: Asymmetrical waveforms !

Post by Ant »

With the merc aerodynamic problem, the conditions to trigger the on track issue couldnt be recreated in the wind tunnel or with cfd modeling due to the limitations of cfd, and the boundaries set by the fia in terms of wind tunnel use.
So, the data correlation it could be said doesnt match because the testing methods and perameters are not measuring the right things to detect the problem. A classic case of just because you cant measure it, doesnt mean its not there. And just because you can measure something it doesnt mean its necessarily relevant

Merc need to know what to measure before they can devise a useful test, so the usual tests need to be tested to check that the tests are actually testing the right things, and wether the tests are hinting at the aerodynamic problem, giving a basis to devise a test that measures what they need to measure to overcome their problem.

It also highlights that some legacy tests they run may now be largely irrelevant to the new cars, i.e. the test results look good on paper, but in practice are not making the car faster, and could be contributing to make it slower.

The rumour mill at pre season testing was that the merc data showed an absolute rocket of a car that would smash everyone else, but what actually hit the track was actually rubbish compared to other cars because of the undetected problem. So was the data wrong? No, it was incomplete, leading to the wrong conclusion on its projected performance
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steve s
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#109 Re: Asymmetrical waveforms !

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Ant wrote: Sat Jun 04, 2022 11:38 am.
So was the data wrong? No, it was incomplete, leading to the wrong conclusion on its projected performance
To me, that's sounds like a fairly accurate description of what's wrong in hi fi land ?

I would hazard a guess that the losses in all but the very best measuring equipment would also be a good start.

An extra cap in line is audible in my amps, or a carbon pot, ..so I'd guess most measuring equipment also doubles as up as a filter.

At a recent bake off I attended,
There where a couple of systems playing, both didn't play the background detail in the music very well.
One in particular, to my ears only played the 'tune' if you know what I mean.
Probably 15 dbs down, the music started to disappear.. but the sharp leading edges and tone lacked at everywhere.
That just confirms to me the real usefulness of whats actually measured.
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IslandPink
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#110 7th is death

Post by IslandPink »

Some interesting thoughts from John Curl .
Start at 33:20 for some thoughts about specific harmonic distortions :
"Once you find out ... the Circumstances ; then you can go out"
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Nick
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#111 Re: Asymmetrical waveforms !

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On the subject of the 7th harmonic I thought I would check it out, and its correct (not that I thought it wouldn't be, but reviews and all that). Looking at the first 9 harmonics of a C, I get the following (error is in approx cents)

Code: Select all

Harm    Freq        Note    Closest     Error       Tone
F       261.63      C4                  0           1st
H2      523.26      C5                  0           1st
H3      784.89      G5      783.99      +2          5th
H4      1046.52     C6                  0           1st
H5      1308.15     E6      1318.51     -13         3rd
H6      1569.78     G6      1567.98     -2          5th
H7      1831.41     A6      1760.00     +68         between 6th and #6th close to #6th
H7      1831.41     A#6     1864.66     -30
H8      2093.04     C7                  0           1st
H9      2354.67     D7      2349.32     +4          2nd 
H5 is a little crunchy as well, but H7 is certainly the one that's between western tones.
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