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Give me ultimate proof... |
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Graham Slee
Admin Group Retired Joined: 11 Jan 2008 Location: South Yorkshire Status: Offline Points: 16298 |
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Posted: 12 May 2008 at 6:38pm |
@dvv, or anybody else professing a knowledge, this is my challenge: Give me ultimate proof beyond all doubt that;
1] there is such a thing as damping factor (I never heard about it in broadcast audio!) 2] and therefore prove the case that headphone amp output impedance must be some fraction of headphone impedance. I will expect a proper mathematical argument that is not subjective in any way. I have thrown down the gauntlet. |
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Graham Slee
Admin Group Retired Joined: 11 Jan 2008 Location: South Yorkshire Status: Offline Points: 16298 |
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Ah well, 14 hours have passed by so I guess there must be other pressing issues affecting the technical minds of this community, so I'll start us off...
What is the impedance of the load? Is it pure resistance? If it were pure resistance then there would be no need for this imaginary thing called damping factor? If it is not pure resistance then how do we express the load's impedance? If we don't know the thing that isn't pure resistance how do we express this other thing? Maybe we don't know what this other thing is? What does the mathematician call something that is an unknown, or something that in itself is unsolvable? An example of an unknown or unsolvable number is the square root of minus eleven! Try working that out! It is however, a number. So how does the mathematician account for numbers like that? Imaginary numbers! Have you ever seen the notation j in a mathematical formula? Therefore, if the load isn't pure resistance, and this other part of the impedance is not known we call it j. And so the load resistance can be expressed as jx Ohms. (x being the real part) Somebody willing to take it from here? |
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It's a lorra, lorra years since I took GCE "O" Level maths and physics so I'll leave this to others .
Meanwhile I will continue my search for a pesticide that I can legally use to control red ants in customers lawns. Strange that nothing is cleared for such use!
Graham, you have your concerns with the good ole EU, but they are are making my job a misery too
Adrian.
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Dave Millier
Regular Joined: 29 Feb 2008 Status: Offline Points: 67 |
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Graham
Are you mis-representing imaginary numbers and complex mathematics on purpose to suit your thesis? I'm sure you know perfectly well that the square root of -1 (i) is *defined* in mathematics and there is nothing dodgy about complex maths.
As to how this related to "damping factor", I haven't a clue.
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Graham Slee
Admin Group Retired Joined: 11 Jan 2008 Location: South Yorkshire Status: Offline Points: 16298 |
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Read it again David, "square root of minus 11"
Damping factor is expressed as load impedance over output impedance, Zload/Zout. Assuming Z = resistance, we are given glib results based on nominal loudspeaker impedance. But the loudspeaker is far from a constant Z, more like jZ, and inside the audible spectrum. Therefore damping factor is one of those terms invented by hi-fi, which serves no purpose other than showing off. It was probably conceived to explain to the average man how output impedance compares with load impedance, but it hasn't worked, going on the number of inquiries I get about cartridge matching and matching one piece of equipment to another. The result is most people think that the higher damping factor can stop the mechanical forces of a loudspeaker dead. Not the case in my observations. And if it can't do it for a speaker it can't do it for anything. |
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Graham Slee
Admin Group Retired Joined: 11 Jan 2008 Location: South Yorkshire Status: Offline Points: 16298 |
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PS. My error, I was educated using j instead of i
(perhaps j was too Jehovan?... ) Edited by Graham Slee - 13 May 2008 at 3:49pm |
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Dave Millier
Regular Joined: 29 Feb 2008 Status: Offline Points: 67 |
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I'm afraid "load impedence" and "output impedence" are as much of a mystery to me as damping factor as I know nothing about electronics!
But I take your point about loudspeaker impedence. I've seen graphs from the old days of Hifi Choice when they cared about such things that showed loudspeaker impedence going all over the place. One reason for claiming that power amps needed 50amps of peak current output I seem remember - why was the NAD 3020 better than 200W behemoths? Current delivery. Or so they said. Must have been right then ;-)
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