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Re: John Curl, you still grabbing at straws??

Posted by john curl (M) on November 24, 2002 at 11:07:41

In Reply to: John Curl, you still grabbing at straws?? posted by John Escallier on November 24, 2002 at 10:16:17:

John Es, you have accused me of 'whining' and I have accused you of 'sniping'. Let me define what I mean by 'sniping'.
To me, 'sniping' is the criticism of someone elses research without attempting to verify or ascertain whether your criticism has any merit. So far, you have 'sniped' Hummel, Hawksford, and me, in that order.

For me, 'sniping' is related to 'refereeing' because that is where it does the most damage.

For everyone, this is what happened at an IEEE Conference on TIM at Tulsa in 1978. Walt Jung and I had completed giving our respective papers on (TIM or SID) when Walt recognized Dr. Ashley in the audience. He asked Dr. Ashley, in front of me, why Ashley had rejected his paper written specifically for the 'Journal of the AES' where Dr. Ashley was a referee at the time. Dr. Ashley responded that "he didn't like the math". He was referring the the 'Volterra series'. Dr. Ashley didn't try to PROVE that there was anything wrong with the math, and he never did show that anything was wrong, he just expressed his uninformed opinion.
I knew something about the 'Volterra series' because I studied it at UCB in the same graduate class as the co-author of Walt's Paper and this is where it had originally came from. Walt's paper wound up published in 'The Audio Amateur' and this started a long tradition of using alternate venues, rather than the AES.
This is 'sniping' folks.
As far as my measurements are concerned:
Engineers know that the underlying basis of any harmonic distortion is a deviation in the transfer function, which ideally should be a straight line. I am looking for 'kinks' in the transfer function. Harmonic analysis is one of the LEAST SENSITIVE methods of measuring the underlying non-linearity, but it is relatively easy to do, and we can measure extremely low levels, BECAUSE we can null the original signal. Actually, a multitone IM signal would be better, and real music would be better still.
Fortunately, a single harmonic can predict that there is an even greater amount of distortion generated with real music, but I just can't directly measure it at this time.
It is also true that I am using a 5kHz signal, for convenience. I could use a 500 Hz signal and then the 7th harmonic would fall at 3500 Hz. However, my THD analyser is 25 years old and does not want to null at 500 Hz without me readjusting it, while also measuring at the LOW LEVELS necessary for this test. The non-linearity that I am measuring will track with frequency. At higher input levels, the distortion goes away, as this a crossover type distortion, rather than a simple nonlinearity, so I am running my distortion analyser at its operational limits. This is why this sort of distortion in wires goes unnoticed,because nobody looks at wires at lower voltage levels, where they actually operate in audio systems.
To criticise my efforts at this point is 'sniping' as you have refused to consider what I just stated, and your intent is to block my input rather than to constructively criticise it. I knew this from the first, so I originally responded as to your 'intent' rather than the specifics of your question. I hope that this clarifies the situation, however, I will always have critics just like my friends. Oh well. ;-)

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