Impedance curves for conductors

I haven’t managed to find measured impedance curves for different metals. I don’t see what else would precisely quantify the audible differences between metals used as conductors - for example silver is perceived as generally “brighter” than other metals so it seems obvious that silver’s impedance curve drops more rapidly as frequency increases than, say, gold’s.
Of course the matter is very complex and includes metallurgic factors at the lattice level, conductor geometry, the lot of it, but I’m just interested in seeing some measured results that correspond to the general characteristics of different conductors in audio systems.

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impedance of a cable is very dependent on the geometry, not just the metals involved :slight_smile:

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And of course the frequency and current of the signal as well as environmental factors. My guess is @rower30 has papers on just these parameters.

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When you change metals, you adjust for the skin depth and resistivity values. Aluminum is actually pretty darn good or audio if it didn’t work harden at the sizes necessary for reliability.

Many speaker voice coils are aluminum to lower the overall mass effectively as the wire is FIXED in place and can’t work harden, for instance.

More and smaller wires with a HIGHER DCR will improve the sound. Stick more in parallel to equal other metals DCR. When we get the aluminum DCR in spec (make them strands bigger) compared to the copper wire it is still too brittle.

It’s all a balance on the resistivity and skin depth. Copper is far and away the easiest to work with at decent value points. Silver and gold are good, too, but expensive.

Cable impedance is a simple phrase; physicals equals electricals.

Change the materials, DISTANCE and/or dielectrics and the impedance curve will change.

Galen Gareis


If we want to define impedance (not resistance) characteristics for pure elemental metals at given temperatures,… why don’t we have such charts, actually?
Having a perfect monocrystalline conductive sample of an element isn’t that hard to have and to measure electrically. Of course the measurements should be standardized so that we have the same conductor structure for each being measured, etc.

rower, do you know to tell about some specific alloys that have beneficial properties over some elemental metals as conductors (used in audio)?
I know that brass is used for platings commonly and isn’t actually bad at all if it’s of proper metallurgic quality.

Here is where I can’t over step what I know from calculation and measurements…HOW a metal sounds, not just measures.

This is why we offer several choices in ICONOCLAST as we do have a preference for what we consider “beneficial”.

I do have a tech paper on materials if you want it. Kind of dry as it is just numbers and materials.

Galen Gareis

It isn’t sensible to attempt to correlate the electrical characteristics of a bare conductor in isolation to SQ because using bare conductors in an audio system isn’t practical. While it might be possible in principle, nobody I know uses bare conductors as interconnects, speaker cables or in digital applications. It is like attempting to correlate how a car would handle when the only part of it to be characterized is the engine without consideration of the body, suspension, tires, etc. IMO the question only makes sense when combined with the insulation materials and geometry being considered for a cable design. I’m going to go further by stating at audio frequencies (RF is a different ballgame but home audio is nowhere close to operating in RF) geometry and insulation materials are more important than conductor type for the overall complex impedance and group propagation in a cable. When I do skin depth calculations for the 20-20khz range I simply can’t convince myself silver is anything other than bling factor to justify higher prices. I don’t find in practice that silver is ‘brighter’ than copper all other factors being constant.

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I seem to remember Paul saying the material used for the sleeving causes chemical interactions effecting sound quality of cables as well

Why not just make a same length same gauge monocrystalline piece of conductor from all commonly used metals and their platings, copper, silver, nickel, rhodium, gold? Then measure the impedance curves for those wires?
People say that to their ears a rhodium plating offers a neutral, balanced, well-refined sound even though its about twice less conductive than gold which is described as somewhat warmer overall? Doesn’t this hint that gold, as a conductor measured against rhodium in a standardized test would show higher impedance toward the top end, what else would explain the common perception that it really sounds warmer in comparison?

And how come so many people just love their JPS Labs aluminium alloy cables despite how “bad” aluminium is as a conductor? Maybe a curve would shed some light on this rather than a harshly defined overall resistance.

All audio cables will have a significant rise in impedance as frequency decreases. None can escape the physics. The conductor material won’t change that property significantly. R and C are in the denominator of the equation that defines Vp through the audio range. As Vp and resistance drop, impedance rises, a lot.

Skin effect and proximity effect are also improved when you address Vp through the audio frequency range. It is all in the math. Many are addressing skin and proximity effect without the knowledge of what those specific properties do to the Vp linearity through audio band. Many that do know, don’t make the Vp non linearity public as it tosses out a lot of the miracles of cable out the window. Cable can’t be a flat impedance or anywhere near eight-ohms.

I will have a paper on this on the web site, or just ask me, shortly. It is all there, Substitute conductors properties and the answers will be close to copper. The data isn’t new, it is a hundred years old or more and verified over and over again. I provide two separate sources with the exact same conclusion as the math says that will be the case.

Incidentally, aluminum is a GREAT wire to consider for Audio as it has a DEEPER skin depth compared to copper (gains better current uniformity at the same size, and the increased resistance can also be used to flatten Vp linearity.

OK, that’s the numbers. Aluminum is too fragile to use in the sizes we’d need. The benefits stay largely on paper. Copper still wins. What we hear in different RESISTANCE wires (we can use differing wire materials to do this) can be partly explained by how the Vp properties follow the wire’s resistance and current efficiency (skin and proximity properties).

The fundamentals are there, increase DCR and capacitance to improve Vp linearity through audio frequencies. How you do that isn’t always clear as this is a geometry problem.

Galen Gareis

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Exactly. I’m appalled at how bad the high-end industry is at hiring mathematicians. Einstein had to hire a mathematician.

“How a metal sounds”—Can we assume that silver plated copper sounds different from, say, TPC because the silver plating creates a smooth surface, free of the TPC or OFE crevices, just as OCC is?
Am I making any sense at all?

I’d think silver-plated copper creates its unique “discrepancy” of high-mid to high freq flow. An abrupt transition with a highway for highs, you know…

My common sense tells me a single conductor is always best, the best being cryo-magnetically treated pure silver. In what geometry, who knows…

But I’m not Galen, so.

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Let’s think about this a second. A 6-8 GHz coaxial cable exhibits almost pure surface skin effect properties. This high frequency cable works flawlessly with the same conductor we use for the SPTPC speaker cables.

Which one do you think would rat out “surface defects” better based on skin depth? Certainly not the “low frequency” audio cable. The 6-8 GHz coaxial has virtually all the signal in the outer skin!

I don’t think that the surface is the issue that makes the wire sound different. I know we are supposed to think that, but isolating the effect and measuring performance WAY up there where it matters most doesn’t show there is a problem.

By the way, the TPC copper is also super uniform, too. It can reach the same RL performance, and indicator of dimensional accuracy, but with higher attenuation as silver is a better conductor if leveraged at super high frequencies.

Does eliminating the surface issue allow me to make a conclusion what it is? Nope.

Wire doesn’t have an “impedance” so much. If we run current through it, yes, we see self inductance that forces the current to the surface, exhibiting higher resistance as we go p in frequency so we can sort of say that’s and “impedance” as we are using AC verses DC.

If we add enough current, we get proximity effect between two closely spaced wires. This further reduces the are of the wire used to carry current.

None of that is changed by so called perfect surface copper. Copper RF wire is run through a diamond swaging die to get the dimensional variation to less than 0.001".

Galen Gareis

Pure silver has issues with controlling Vp linearity because it has lower DCR. That variable is in the Vp linearity equations denominator, opps. We need a bigger value there. But at the same time the aggragate DCR value needs to be LOW, true. Silver can complicate that balance.

If we don’t need aggregate CMA area, is silver really better in a solid form? Depends on what you need to fix, yes?

Cryo is used to relieve built-in stresses and with some metals improve wear properties. Cool it down SLOWLY and SLOWLY raise it to room temp. The conductivity stays the same unless some real issues were involved in the process. Copper needs to re-annealed after cryo if Tensile and Elongation are under ASTM standards for full soft anneal.

As we sweep frequency throght to 10 GHz on a coaxial test cable, the attenuation trace shows no deleterious effects going from the copper to the silver layer that would effect audio or RF any at all. The SLOPE of the curve changes WAY up there as it transitions to silver, that becoming the only conductor.

I know we are told bonding silver to copper using an electroplating process is supposed to add impurities between the silver and copper but super critical RF frequencies would really show the problem if it exists.

For some reason, we expect the frequencies that are least able to exhibit problems to show the most problems. Why not isolate the issue to the frequencies most sensitive to it?

So no, I still don’t see indicators that silver plate causes problem through the audio band at all. What we know isn’t telling us what we want to know just yet.

Galen Gareis

Thanks Galen.
It’s a “wonderment”. The RCA’s of yours that I use and very strongly prefer, are the OCC version. But it’s hard to get my arms around why the OCC particularly.
So I’ll just put my confusion to the side and enjoy what I’m hearing!


I agree with the confusion on copper. Why is copper structure effecting the EM wave? How? There are no current repeatable tests that show in dv/dt domain what is going on. None. It isn’t conductivity as changing the length of the wire would have dramatic effects on the sound. Grains do change conductivity.

We can isolate the copper so users can decide if they hear a change. But, we can’t provide information to PROVE, verses people agreeing, it is different. It has to be a repeatable test as FACT before this is cleared up. It isn’t.

I can’t point to measured or calculated copper changes I’m making that are evident through those tasks to change the cablee EM properties, measurably. We can argue how fine changes are to hear, but they have to be there and repeatable before we say it is better on a design / measurement basis.

Galen Gareis

Galen, since you too bring up the point of aluminium not being a terrible conductor (as is apparent from JPS Labs aluminium alloy cabling being highly regarded), would you say it has any use in speaker cabling, or just interconnects?
How much does skin effect depth (in benefits) depend on whether it’s a voltage or current transferring cable? For I see no aluminium speaker cable on market, only interconnects.
If we were to utilize aluminium for efficient speaker cabling, what simple requirements would increase? I’ve come to understand that this is not about a necessary increase in cross sectional area as much as we would think?