speaker cable myths and facts

[ThorstenL]

Hi,

What you are hearing is not 'distortion' but the impedance curve of the loudspeaker translated into signal level.

That remains to be seen/heard. The distortion levels Duncan et al demonstrated may very well be audible, depending on their spectrum.

Of course, if all we hear is the original signal, attenuated and possibly somewhat unequalised, then the errors are linear in nature, but if not...

One can also apply FFT to such signal and many others...

You will get a similar effect by feeding the speaker through a small resistor (with very short cable) and listening to the voltage across the resistor.

This is based on actual experiments and tests, or is it based on what believe should happen?

If done with a dummy load instead of a speaker you are listening to the impedance curve of the cable. Not very interesting, unless you have a bad contact somewhere - then you may get genuine distortion.

Than would you care to explain the results obtained by Duncan at al in the 1999 tests published in HFN (cited earlier)?

Ciao T

 

[SY]

DF96, if you don't have a copy of the articles Thorsten referenced, the test setup (and the results) are described here:

Current Dependent Phase Shifts in Audio Cables?

 

[ThorstenL]

Hi,

Current Dependent Phase Shifts in Audio Cables?

Either this discussion is for tests that are different from the one I was intending to reference, or it omits several highly relevant sections of the original tests and focuses only on one section.

The tests I intended to reference also covered several issues but operated essentially as null test. It included (T)HD measurements for the cables. The general time and content seemed right, I apologise if I got the wrong test.

Hence my request for scans...

Ciao T

 

[scott17]

OK great article! This thread can finally be closed.

All you have to do is use speaker cable of the appropriate gauge.

Other than that there is no audible difference between brands of cable regardless of cost.

 

[SY]

Either this discussion is for tests that are different from the one I was intending to reference, or it omits several highly relevant sections of the original tests and focuses only on one section.

For the tests you mean to cite, what was the difference in the test setup?

 

[DF96]

Thanks, SY. I was having a look around the web, but didn't find anything apart from a long report by Ben Duncan on woven mains cables. This reminded me of his writing style, which I remember back in the days I used to read HFN/RR before it went too subjective.

Incidentally, I knew Jim Lesurf many years ago. He was a postdoc in the same physics dept where I was an undergrad and postgrad. He did some audio design as a sideline to his astrophysics. His website is worth reading for anyone who is in danger of being confused by audio fashions.

 

[ThorstenL]

Hi,

For the tests you mean to cite, what was the difference in the test setup?

They included a "null-test" arrangement similar to that described earlier in the test, however evaluation was not using a 'scope", instead the residuals where analysed among other factor for THD/Noise etc.

The Table of the cables in your reference looks pretty much like what I remember, however Jim Lesurf does not mention these parts, but concentrates only on the Inductance. This does not mean it was not contained in the tests of course...

Ciao T

 

[DF96]

For further comment on speaker cables see Jim Lesurf on how short is a piece of string? This doesn't answer all possible questions, but it does show that for audio signal purposes the lumped approximation is good enough up to about 50kHz. RF is different, so where EMC is an issue (almost everywhere?) things can get more complicated.

Note that if the lumped approximation is good enough, then cable or connector non-linearities (if they exist) can be handled as a non-linearity of the lumped parameters. This should remove some of the mystique.

 

[a.wayne]

Hi,



Sorry, non left except what is in my personal system and that is not for sale.

Some dealers do have cut length available, I have no specific examples.

Look for SCSI III Cable, FEP/PTFE Isolation, Silverplated 30awg solid core copper condcutors. There are at least two factories, one makes it with red stripe the other blue.

In a pinch, 3M #3749-80 will also do, this should be readily available.

This uses TPE insulation and tinplated conductors. Some may feel that these are inferior to the spec I use, in my own tests I quite liked the 3M cable but I never compared them side by side. Certainly the grey TPE looks way less cool as the clear Teflon over silver...

Ciao T

Thanks for the heads up ..... is this similar ..?

http://www.awcwire.com/ProductSpec.aspx?id=TPO-Microzip-Ribbon-Cable

edit: just looked at the specs ....nope !!!!!

 

[SY]

They included a "null-test" arrangement similar to that described earlier in the test, however evaluation was not using a 'scope", instead the residuals where analysed among other factor for THD/Noise etc.

Thanks. So presumably the test setup artifacts described by Prof. Lesurf will remain for the other analytics?

 

[ThorstenL]

Dear Sy,

Thanks. So presumably the test setup artifacts described by Prof. Lesurf will remain for the other analytics?

I believe to debate a given publication third hand based on some-ones critique of it (which may or may not be correct), even if it someone like Jim Lesurf is futile, if conceivably diverting, just like William Cowpers story of John Gilpin...

The first step would surely be to obtain the original publication and then work from this, both to see if this is the test I meant to reference and if it is to check what was tested, how and what the results where...

Ciao T

 

[SY]

OK, when you figure out what it is you want to reference and find a copy to see if it says what you think it says, then we can see if it says what you say it says.

 

[Joachim Gerhard]

In 2005 i did some measurements on cables. The result was discussed on a german internet
forum. The differences where considered too small to be audible. So here we go again. The differences are not audible but i can measure them. It is the other way around this time.
Usually people hear something and can not measure it.
Excuse the rather fruity language. That came from the marketing people.

 

[Joachim Gerhard]

I tried to upload the measurements but it did not work. I try again later.

 

[DF96]

I realise that this is only weak evidence but here is a discussion about the articles (and other things). The comment is made that

"To remind anyone that didn't read the original articles, the claim was that there was a difference in phase shift caused in these speaker cables that seemed to depend on the magnitude of the current used in the test.",

implying that this was the main result of the test. Jim Lesurf seems to have seen that one off so were there other minor results which don't depend on the major (now debunked) result?

 

[ThorstenL]

Hi,

"To remind anyone that didn't read the original articles, the claim was that there was a difference in phase shift caused in these speaker cables that seemed to depend on the magnitude of the current used in the test.",

If such a mechanism indeed existed, that is signal dependent phase shift (and it actually is plausible to exist as a purely mechanical deformation of the cable with signal modulating in the form of magnetostriction between current carrying conductors) it would also show up in HD measurements.

implying that this was the main result of the test. Jim Lesurf seems to have seen that one off so were there other minor results which don't depend on the major (now debunked) result?

Well, Jim Lesurf has not really dispatched much, now has he. He merely claimed to do so.

For example, IF magnetostriction varied the geometry with signal and thus the cables LC parameters nothing would be debunked, merely explained.

Note, I do not claim that magnetostriction and resultant LC parameter variation (which are very real and affect some cables more than others, cables that soft and limp for example are more subject to these than more rigid cables) cause the measurement results, after all, we are still talking third hand and I only have some fairly hazy memory of the precise details.

Ciao T

 

[DF96]

He merely claimed to do so.

Lesurf showed that the claimed phase shift was not caused by "signal current" but change in terminating impedance, unless you are disputing his arithmetic. The experimental measurements from the article sat quite neatly on or near his theoretical line.

Any remaining minor differences may be due to experimental error or the second-order effects you mention. If someone says "I have detected something new", then someone else explains roughly 100% of it using normal circuit theory then the most likely conclusion is that nothing new has been detected.

I note that Ben Duncan is a consultant to Jenving, who make Supra audio cables and believe in cable directionality - apparently the signal has to flow in the opposite direction to the final die drawing of the copper wire at the factory. They say on their website that "Simplistic electronics theory says there is no ‘directionality’ in conductors, but assumes conductors are perfectly isomorphic." I'm not certain they mean 'isomorphic' - perhaps 'isotropic' or 'laterally symmetric'?

 

[jcx]

are there audiophile approved diodes for switching the signal to the appropriate direction wire?

 

[vacuphile]

I note that Ben Duncan is a consultant to Jenving, who make Supra audio cables and believe in cable directionality - apparently the signal has to flow in the opposite direction to the final die drawing of the copper wire at the factory. They say on their website that "Simplistic electronics theory says there is no ‘directionality’ in conductors, but assumes conductors are perfectly isomorphic." I'm not certain they mean 'isomorphic' - perhaps 'isotropic' or 'laterally symmetric'?

I think the same effect can be achieved by controlling the incline from the cable connecting your amp to your speakers, which, like in plumbing, should be 1.5 cm/M or more. Myrthle blocks work best for implementing such set up. ABX-ing is unfortunately not possible because that would upset the run-in of the cables. Measurements can't be done because of the Heisenberg uncertainty principle, which rears it's ugly head at this level of precision.

 

[ThorstenL]

Hi,

Lesurf showed that the claimed phase shift was not caused by "signal current" but change in terminating impedance, unless you are disputing his arithmetic.

Jim Lesurf showed what he showed, if that really relates to the measurements and the article would need me to have the article at hand, which I do not.

The experimental measurements from the article sat quite neatly on or near his theoretical line.

This does not make his thesis automatically true.

Again, we are debating third hand, there is simply no debate that has a point until we have a copy of the original publication at hand.

I note that Ben Duncan is a consultant to Jenving

Sure. So what. And what about what the company "believes" in? I am not interested in debating this kind of stuff. It's below the belt line.

We can either debate published tests (which would no doubt please the moderators) once we have what is published. Or we can engage in more of what may be likened to certain acts of self gratification, with no tests, no facts, hearsay and trying to cast doubt on others reputation and/or honesty.

I'll see what I can dig up and leave you to your own style of debate, I'd love to be in with it, but I cannot stoop so low, bad back I'll have you know...

Ciao T