I wouldn't think higher maths are required for this. Speaking of wires and professors, the Hawksford affair comes to mind.
My PhD advisor was, no joke, a student of Manfred Eigen, the great kineticist and Nobel laureate in Chemistry. So indeed, he literally was an Eigenstudent.
Hey, we found the very shovel that dug the ditch! There's a big difference between what is physically true, and misapplication of it to audio.
The concept of TL settle time simply has no context or meaning here.
This is because there is no 'transition' to settle in TL terms, even the fastest 'transition' in audio appears as a slow continuous function in the scheme of things. In this case, treatment of the superposition of the incident waveform and the infinite discrete reflections by calculus is long established - the line 'disappears' no matter what source or termination impedance is applied, and behaves as a plain wire with lumped properties. The driver simply sees the load impedance, and the lumped cable parameters.
Here's a common sense reductio ad absurdum point. Say there's an infinitely fast step change, which is then bandwidth restricted to audioband and applied to drive speakers via audio cables. So the driving waveform has a characteristic ramp curvature, and has a rise time representing the fastest possible 'transition' in audio programme material, and this is 1000s of times slower than speaker cable round trip. Proposition is that the resultant waveform at the speaker deviates from the driving waveform so as to have artifacts of 1000s of reflections by way of inflections of some sort. However each deviation must comprise in part a rise time faster than that of the driving waveform, ie faster than the fastest possible transition in audio programme material, which by definition is inaudible, having an out of audioband spectrum...........
I would be careful about your meaning of misapplication. What is physically true describes reality (in this case) exactly. It is important to put boundaries on when approximations are sufficient, whether or not they apply in this particular case.
Misapplication seems an OK description to me.........
Here's another example which has no context in audio, the flip side of the TL coin:
Capacitors behave as open circuit transmission lines.
Physically true, being rolled up parallel plates of conductors with a single point connection when you think of it. And if one deals with short enough events and fast enough rise times, it's observable in full glory, with all expected properties.......reflections from edges of foil and all - I've seen it first hand. But this property of capacitors is only relevant when events are so fast that it matters, and that obviously excludes audio being many orders of magnitude too slow. No-one ever even thinks of it in passing in audio, it would be silly. Nevertheless I expect once one becomes aware of it, expectation bias might kick in and try to shoehorn it into explaining a whole set of phantom capacitor audible effects, and someone seems bound to propose convincingly that capacitors have various settle times based on thousands of unterminated round trips..........
'All the world's a transmission line', as Shakespeare said I think.
Here's another example which has no context in audio, the flip side of the TL coin:
Capacitors behave as open circuit transmission lines.
Physically true, being rolled up parallel plates of conductors with a single point connection when you think of it. And if one deals with short enough events and fast enough rise times, it's observable in full glory, with all expected properties.......reflections from edges of foil and all - I've seen it first hand. But this property of capacitors is only relevant when events are so fast that it matters, and that obviously excludes audio being many orders of magnitude too slow. No-one ever even thinks of it in passing in audio, it would be silly. Nevertheless I expect once one becomes aware of it, expectation bias might kick in and try to shoehorn it into explaining a whole set of phantom capacitor audible effects, and someone seems bound to propose convincingly that capacitors have various settle times based on thousands of unterminated round trips..........
'All the world's a transmission line', as Shakespeare said I think.
It was one of those situation in which a little physics-educated common sense allowed a person to say that the prof must be wrong, but it needed some fancy maths to explain in detail exactly how he was wrong. My understanding is that the physicists were hoping to avoid a public humilation of their engineering colleague but he would not shut up so eventually they had to go public in order to maintain the reputation of the institution as a whole.scott wurcer said:
I used to see Prof Eric Laithwaite in the coffee bar at IC. He was a bit of a legend to the students. This is the man who could really surprise you with some of his electromagnetic demonstrations. A sort of magnetic gun that fired a copper ring up in the air at high velocity! I think he designed that bit of fun at the Science Museum where a falling copper coin slows briefly to a halt when it passes through a high magnetic field due to current induction.
His field was electric motors in the heavy engineering department. He invented the MagLev train principle and linear induction motors to propel them. I guess the Japanese Bullet Train is his lasting contribution. Which is quite something IMO.
The gyroscope anti-gravity business was rather interesting. Gyroscopes are counter-intuitive. His gadget did sort of take off, but then it came down again. I don't think anyone had ever tried it before. But I wouldn't dismiss him as a simpleton. He was having fun with something new, and sharing it.
Prof. Stephen Hawking get egg on his face with the Black Hole Entropy business. Prof. Susskind and Prof. 't Hooft got the right answer. They sat at the back of the hall and realised that if he was right, most of the established physics would fail. That was real insight. Doesn't make Hawking an idiot. He was the first person to even think about it.
His field was electric motors in the heavy engineering department. He invented the MagLev train principle and linear induction motors to propel them. I guess the Japanese Bullet Train is his lasting contribution. Which is quite something IMO.
The gyroscope anti-gravity business was rather interesting. Gyroscopes are counter-intuitive. His gadget did sort of take off, but then it came down again. I don't think anyone had ever tried it before. But I wouldn't dismiss him as a simpleton. He was having fun with something new, and sharing it.
Prof. Stephen Hawking get egg on his face with the Black Hole Entropy business. Prof. Susskind and Prof. 't Hooft got the right answer. They sat at the back of the hall and realised that if he was right, most of the established physics would fail. That was real insight. Doesn't make Hawking an idiot. He was the first person to even think about it.
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Generally, after rolling, the edges of the foil (ends of the roll) are sprayed with zinc, so the connections are all along the electrode, not just a single point.
He'd get a nobel prize if he could do that with copper. I made a linear rail gun at school. We could get an aluminium ball about 60ft in the air.
You went to Imperial or just mates with someone who went there?
What's the issue, buddy? What is your problem? Does aluminium work better? I don't know. It was 30 years ago.
Tell me something interesting, and less of the personal sniping. OK.
Basic A level Physics. Don't claim intellectual high ground if you can't get what 16 year olds are taught right.
The high ground is using some advanced mathematical techniques. In fact it's often the proper technique, rather than some quick and dirty approximation. Like projective geometry, which sees all triangles and conics and quadratics as just ONE triangle and ONE circle and ONE quadratic viewed from different points! Amazing. They are all the same!
I did Basic "A" level physics too. It was good. I went further. But what is it I am not getting?
Why does aluminium work better than copper in these sort of magnetic coil guns? Or why doesn't copper work? That's what I am asking. Do explain. That would be interesting. We might even learn something about cables from that.
Aluminum has about a 2:1 advantage over copper when weight is considered along with conductivity.
That might be the reason for using aluminum.
"But what is it I am not getting?"
Forget all the physics fantasies, what you seem not to GET or have attempted to explain or justify, is your understanding of short cable transmission line characteristics AT AUDIO FREQUENCIES.
I am beginning to conclude that you really DO NOT GET what this is all about!
Just try going over that again; the relevance to speaker cables, lifters &c and forget the rest of the off-topic distractions.
Forget all the physics fantasies, what you seem not to GET or have attempted to explain or justify, is your understanding of short cable transmission line characteristics AT AUDIO FREQUENCIES.
I am beginning to conclude that you really DO NOT GET what this is all about!
Just try going over that again; the relevance to speaker cables, lifters &c and forget the rest of the off-topic distractions.
Simply, and utterly, incorrect.
The only argument to be had is whether or not the use of T-line is needed, vs the simplistic RLC approximation.
I ignored the rest of you post so will not comment, not because I hate you or think you're dumb. (I do not on either count). Merely because you do not yet understand what is being discussed. I suspect that when you understand, you will change your mind. You've learning to do with respect to what I've been saying, I am patient.
jn
Finally I think we totally agree, and thanks the brain exercise keeps the Alzheimers away. There is an impasse here that is for some reason totally ingrained in some, I don't think further discussion at this time is productive. I wish Bateman's article had a wider audience (even if he did steal my oscillator). 😉
I think you're right, Tom. Aluminium is lighter. But copper works too. Whereas billshurv was poo-pooing the idea and Prof Laithwaite's experiments. I think he was wrong.
SY made an interesting observation that clear cable could be very bad for oxidisation due to sunlight and corrosion with a poor dielectric. Good. A takeaway at last.
I can't apologise for using the correct transmission line method with all frequencies on cables. A lumped LCR approximation is a low pass filter, and that isn't what really happens.
Now if you are of rather limited ambition, you could just say cable is cable and any odd effects are negligable. So cable lifters are just a waste of time.
I sure don't want them. So I looked at some of the other things we do to make cables and amps and speakers work as well as possible. That's called an engineering solution. And that was all in the first 10 pages. The rest has just been an ugly spat that does this forum no credit. It certainly left the original poster angry.
SY made an interesting observation that clear cable could be very bad for oxidisation due to sunlight and corrosion with a poor dielectric. Good. A takeaway at last.
I can't apologise for using the correct transmission line method with all frequencies on cables. A lumped LCR approximation is a low pass filter, and that isn't what really happens.
Now if you are of rather limited ambition, you could just say cable is cable and any odd effects are negligable. So cable lifters are just a waste of time.
I sure don't want them. So I looked at some of the other things we do to make cables and amps and speakers work as well as possible. That's called an engineering solution. And that was all in the first 10 pages. The rest has just been an ugly spat that does this forum no credit. It certainly left the original poster angry.
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