Instead of pontificating over why the bumblebee can never fly, why not test Blowtorch and put the disbelievers to shame?
It either HAS PIM or it hasn't. We can discuss why when the results are in.
JC, would you like to explain why you are not telling us what you found on the Hirata tests?
Did you know how i chose my cone speakers ? Looking with this typical first little accident in the impedance curve
If i can, one octave lower will be the upper limit with a 24db/oct filter.
This makes-me remember of a legendary hilarious improvised show between two comic French stars.
They were both drunk on the stage. One was dressed as a Fakir, the other plays the presenter..
The presenter ask: "Can-you tell me the age of this man in the audience ?"
The Fakir answer: "Yes, i can".
The other, concluding, appreciative: "YEEEEEES, He can do-it !!!!"
... applauses !
Ahhhh ... no matter how many times I've done it, it still throws me when it happens ... 
With direct relevance to what has just been discussed, good sound is so, so fragile, unless the system has been thoroughly "toughened", as Christophe has confirmed he worries about.
Today, I wasn't happy with the sound -- the giveaway: turning up the volume only made it worse, it steadily became less agreeable, to the point of saying, Turn it off!! But, having been here many times before I started looking for a "problem": hmmm, good, good, good, good ... ah-ha!! A cable had moved perhaps a 1/4 inch from where it should have been, because what it had been sitting on had been disturbed by some other activity. Readjusted, and ... we're back in action. Now, I could turn up the volume and all was fine, relatively speaking ...
A key test, for me, is the ability to go louder and louder with no loss of "musicality", in fact, typically it improves the sound with "cheap" speakers. This slow loss of quality with increased volume I've heard on the most expensive setups, it's a generic problem in audio. The drab, dead sound of most PA systems is an extreme version of this "disease" ...
Frank
With direct relevance to what has just been discussed, good sound is so, so fragile, unless the system has been thoroughly "toughened", as Christophe has confirmed he worries about.
Today, I wasn't happy with the sound -- the giveaway: turning up the volume only made it worse, it steadily became less agreeable, to the point of saying, Turn it off!! But, having been here many times before I started looking for a "problem": hmmm, good, good, good, good ... ah-ha!! A cable had moved perhaps a 1/4 inch from where it should have been, because what it had been sitting on had been disturbed by some other activity. Readjusted, and ... we're back in action. Now, I could turn up the volume and all was fine, relatively speaking ...
A key test, for me, is the ability to go louder and louder with no loss of "musicality", in fact, typically it improves the sound with "cheap" speakers. This slow loss of quality with increased volume I've heard on the most expensive setups, it's a generic problem in audio. The drab, dead sound of most PA systems is an extreme version of this "disease" ...
Frank
It is possible to "build" a cable with similar Zw, but it is not only a "cable" then.
PIM is a result of change (modulation) of -3dB open loop response corner.
My take on FM vs AM distortion (common harmonic distortion) is that they should be considered at least equal in importance with magnitude, until we find otherwise. Therefore the .012% distortion is about 10 times higher than the residual on the HP339, or the ST1700, both common measurement instruments over the last 35 years, and needs to be lowered if possible to separate each IC or amp for its FM component.
At this time, I will not take the position that Paul Klipsch made of the importance of FM or Doppler Distortion (in his case) and AM distortion (the normally measured distortion in loudspeakers, as he presumed FM to be much more (annoying) than AM. Again, I will give them equal value at this time, until research proves otherwise in either direction.
At this time, I will not take the position that Paul Klipsch made of the importance of FM or Doppler Distortion (in his case) and AM distortion (the normally measured distortion in loudspeakers, as he presumed FM to be much more (annoying) than AM. Again, I will give them equal value at this time, until research proves otherwise in either direction.
The situation is that below ka = 2, you want the cone to be pistonic.
But above that, for constant power output, flat response bla bla, the effective cone area has to shrink. This happens through cone breakup so you need to control it with material thickness, stiffness & cone shape. One reason for the dominance of Rice & Kellog's invention is that ALL cones do this in some fashion. Really rigid cones don't do this until much higher frequencies so sound bad.
Our scanning laser interferometry work from the early 80's and Peter Fryers holograms from even earlier allowed us to see this at important frequencies for the first time. But it wasn't until Patrick Macy of PAFEC developed the first usable Boundary Element for air that we could tie this to the FEA. (mid 90s)
I believe I know how a 'plastic' cone should behave for good sound and have had some success engineering this.
But the breakup behaviour of a good sounding paper cone is completely different. Black magic still prevails with paper.
Starting with my dissertation?
This has been my profession for most of the past 35 years.I'm still amazed at the crude state of plastic speaker cones. They could be done sooooooo much better...
As someone who has done original research in quantum gravity and other areas of physics and engineering I am not daunted by things which are "very very complicated", although I will admit that I have forgotten much of the solid-state quantum mechanics which I used to know 35 years ago.mikelm said:
Are you saying that modern audio interconnect phenomena are inaccessible to people with PhDs?
Or could it be that the effects (e.g. microphony, leading to 'euphonic' distortion) are all too accessible to those who know some physics, but denied by others?
Put up a summary of what the "large envelope" might contain. Then the physicists and chemists on here can consider it, and decide whether they wish to see the whole thing.
Hang in there, mikelm. I, too, have a REAL PROBLEM in truly and effectively understanding how current flows in a wire.
Perhaps I have the wrong textbooks?
Let's see: THE THEORY OF THE PROPERTIES OF METALS AND ALLOYS, MOTT/JONES
THE THEORY OF METALS, WILSON
ELECTRON MICROSCOPY OF INTERFACES IN METALS AND ALLOYS, FORWARD/CLAREBROUGH
And finally: ELECTRONIC PROPERTIES OF MATERIALS, HUMMEL
What else do I need to get further enlightenment?
Perhaps I have the wrong textbooks?
Let's see: THE THEORY OF THE PROPERTIES OF METALS AND ALLOYS, MOTT/JONES
THE THEORY OF METALS, WILSON
ELECTRON MICROSCOPY OF INTERFACES IN METALS AND ALLOYS, FORWARD/CLAREBROUGH
And finally: ELECTRONIC PROPERTIES OF MATERIALS, HUMMEL
What else do I need to get further enlightenment?
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The stability is dependent on the phase margin left at the unity gain point. I don't think that detail needs elaboration here, discussion of such is a sidetrack.
Nobody said it was, that is another sidetrack.
I use 350 pS because it's trivially easy. It allows me to determine the health and ability of the current viewing resistor used in a low impedance system. Most get caught in the dB/dt self field problem inherent in most CVR's. One need look no farther than Hawksford's paper on skin effect to note the trap one can think ones self into.
By making my test materials capable of zero overshooot and ringing at sub nanosecond transition speeds, I guarantee performance below half a Mhz.
jn
Start with a book on basic E&M and work the problems. Then go back to some of those specialist texts and read them, rather than having them collect dust until you need to find something to quote out of context. When you get to the point where you realize how ridiculous claims like "slipstreaming electrons" and "near superconductivity" are, then you're starting to actually understand the physics.
This is targeted at Mike as well. Dielectrics are complicated. Simple dielectrics (like plastics) at low frequencies (sub GHz) and low voltages (sub kV) are actually pretty simple. Their effects on low frequency signal transmission are even simpler.
I do not claim any particular knowledge of the physics of dielectrics but in my last job in the US we were working on project involving the behavior of dielectrics.
We employed a physicist with a masters degree join our research team to delve deeply into the theoretical understanding.
During the year that research team was active a fuller understanding was gained but it was not straight forward by any means when considering the effects of different materials, temperatures, applied voltages, and how all of these interacting together "aged" the plastics.
If fact several times the predicted "theoretical models" had to be revised because they did not match our empirical data.
So when someone suggests they can summarise the full story about dielectric behavior on the back of an envelope in a few minutes I'm afraid I don't take it that seriously.
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In all the applications I've done and read about, this has been shown as several orders of magnitude (6 and up) below audio level anything, even mm coils. S/H apps certainly are more rigorous, and it's been done..
While it may sound logical, it is important to understand the level of effect.
Yes, I recall being taught that in an RF class back in '74. I also recall being taught the exponential approximation equation for current density profiles as applied to rf. And then, incorrectly applied for use at audio frequencies.
It is important to think beyond the approximations taught us.
That would be interesting.
My applications range from single digit picoamps to 30 kiloamps, current densities in excess of 3000 amps/mm squared, temps from 1.8K to room, volts from nano to 29 Kilo, and...all at the same time... and yet, nobody I know has any idea what you are referring to..
Do not confuse the inability to measure with the inability to build.
The most salient feature of a T-line is this: the inductive and capacitive energy storage of a signal within a T-line which is propagating at the t-line's characteristic velocity is equal. After that, the understanding is easy.
jn
ps..
e = 1/2 L I I
e = 1/2 C V V
1/2 L I I = 1/2 C V V
L II = C VV
L/C = VV/II
sqr(L/C) = V/I
V/I = Z
Z = sqr(L/C)
(sorry, no equation editor here..) should be...
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That's not the worst approach!
It's not limited to guys at that level either...it happens where I work as well..
edit: well, sometimes it isn't done, and the consequences can be, shall we say, interesting? LHC..
jn
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