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Old 27th September 2010, 10:00 PM   #1
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Default cables for esl speakers

I'm hoping some of you may want to discuss your experiences in finding or building optimized amp to ESL cables. I've read quite a number of white papers on the subject, most notably those of Allen Wright and Rodger Sanders.
Sanders' paper made a lot of sense on a number of levels, and Wright's discussion of skin effect was to me, compelling.
ESL's pose a very unique load. as we know. Stray inductance seems to be the biggest problem, followed by excessive capacitance.
Sanders maintains that cables exhibiting a higher resistive impedance are desireable. To me this makes sense, as ESL's are essentially voltage rather than current driven. To me, this suggests thin conductors- very thin.
Inductance occurs whenever signal carrying conductors are in proximity of each other as I understand it. It can be cancelled to a degree if the opposing conductors cross each other repetitevly as in a braid or Litz confiuration according to several engineers I have spoken to.
Another area I would like to explore is the treatment of the interconnect as a transmission line. Bell Labs established years ago that a properly designed line can minimumize a number of distortion components.
So, friends can we talk?

Last edited by glorocks; 27th September 2010 at 10:02 PM. Reason: spelling
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Old 28th September 2010, 05:33 AM   #2
Calvin is offline Calvin  Germany
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Hi,

as usual with cables there´s no general recommendation of what´s best.
As for example the cited increased resistivity. The upper bandwidth limiting resonance resulting from the stray capacitance of the audio tranny and the panel capacitance requires some damping. The value of the damping resistor can vary between a fraction of ohms to a few ohms. If You use a low output impedance amplifier, like most fed back transistors You certainly need a dedicated resistor to perform the task, because there´s no cable with such a high resistivity. If You use a no-feedback tube amp You might not even need a resistor at all, because of the higher resistivity of the tube amp´s secondary winding resistance. In any way can You tune bandwidth and frequency response of the panel with this resistance. But You can´t recommend a certain value as a onefitsall-value. As with most speaker cables it should be a low resistivity cable to start with.
Since the amp typically sees a heavy capacitive load (in the middle to high frequency range) of couple of µF a additional capacitive load of a few hundreds of pF added by the cabling doesn´t change matters much.
I´d rather opt for a low inductance cabling instead.
But then again, there´s no general rule.

jauu
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Old 28th September 2010, 09:35 AM   #3
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As Calvin says, for an ESL you can use a cable which trades off parasitic capacitance in favor of low inductance, since a little extra capacitance won't make a difference.

The easiest way to make such a cable is from computer flat-cable. Simply alternate between + and - signals: all even conductors carry +, all odd conductors carry -.

As an added bonus it's possible to run this cable under the carpet if necessary

I can post a picture later if desired.

Kenneth
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Old 28th September 2010, 08:08 PM   #4
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Inductance occurs whenever signal carrying conductors are in proximity of each other as I understand it.
No - self inductance increases as the two conductors are moved away from each other. The braiding or Litz configuration is to reduce skin effect on very large diameter wires. Skin effect is not a problem on small diameter ELS cables. Characteristic Impedance is not a factor in speaker length cables.
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Old 29th September 2010, 02:47 PM   #5
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About 25 years ago, I bought 100 feet of 3-wire, 16 gauge, cord made for heavy duty extension power cords, at a yard sale. Each of my tweeters, about 1KV bias, has around 25 feet of it... just in case I move to a big room next.

Can't say as I think (or mic's think) there is any deficiency in my tweeter system. Anybody think I've gone wrong?

On the other hand, when I was working DIY with Dayton-Wright panels, I found it convenient to fish test-lead HV wire for the bias and ordinary wires for the stators through clear plastic tubing. 3-4 KV bias with those panels.

ESL panels are pretty low capacitance so as a high-reactance load, hard to upset them with upstream wires with minuscule losses. Likewise, the whole system south of the power amp is wacky in several frequency-interfering respects which can't easily be assessed.

In short, very low on the list of things worth fussing over, I'd say.
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Last edited by bentoronto; 29th September 2010 at 02:52 PM.
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Old 29th September 2010, 11:36 PM   #6
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I understand the function of the series resistance. Sheldon Stokes mentioned it in his DIY ESL project, and the data that was provided with my transformers (Plitron) suggested a starting point of about 1 ohm.
I suppose I will have to do an RTA to look for that pesky peak and probably have to use the old substitution method to determine the desired value. Thank you for you contribution-
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Old 13th October 2010, 08:30 AM   #7
SM7UYJ is offline SM7UYJ  Sweden
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Hi,

I did a little test a while back.

1.5mm^2 standard "lamp" cable:

Click the image to open in full size.

RG213 coax cable off good quality

Click the image to open in full size.

The big differance is in the phaseshift - 20deg differance at 20kHz!

What it does in reality I do'nt know - Can't hear any differance!

[Connected speakers are my DIY ESL-hybrids]

/R
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Old 19th October 2010, 03:12 AM   #8
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Electrostatics generally look like capacitor to amplifiers, need relatively higher current at higher frequencies. But some are more inefficient than others, need more current. My Acoustat 1+1's are in the super-inefficient category (Black Hole). The bigger Acoustats are actually more efficient, the smaller ones less efficient, that's the way it worked. The more inefficient your speakers are, the more series impedances like resistance and self-inductance matter as they will soak up power in a way that alters frequency response. Given that you are already using 16ga or larger wire, self-inductance is probably a more important factor for electrostatics in modifying their frequency response.

I went from 12ft 16g cord to 4ft. Nice difference. Problem is, I'm going to have to go back to 12ft eventually when I get my old amplifier back. So how do I get the same self-inductance in a 12ft wire as I would get in 4ft 16g zipcord?

I think I will do just that. Many different multiconductor designs will work. I'm thinking of getting some variety of Cardas; they use Litz combinations and specify the self-inductance of their different cables. That's nice. But there are many other cheaper options too, and you can test cheap braided/flat wires to see what their self-inductance is.
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Old 19th October 2010, 04:35 AM   #9
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Quote:
Originally Posted by charlesp210 View Post
I went from 12ft 16g cord to 4ft. Nice difference. Problem is, I'm going to have to go back to 12ft eventually when I get my old amplifier back. So how do I get the same self-inductance in a 12ft wire as I would get in 4ft 16g zipcord?
Or you could run coaxial cable, those have low ESL. I've had good luck with parallel runs of RG-8. RG-58 is lighter, but a lot more tractable than RG-8.
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Old 19th October 2010, 04:36 AM   #10
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Some other low-inductance designs here:

DIY speaker cable for ESL
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