The consensus on cross sectional area

What is today’s consensus on the true need for any substantial cross sectional area in anything other than power cabling?
Apparently analogue signals, from low voltage phono to high current speaker level, need not much cross sectional area to be efficiently transmitted, if the material and geometry are sensible. I’ve understood that cross sectional area is best minimized up to a certain point of trade-off. I understand a foil ribbon cable that trades minimal inductance for higher capacitance can shine in one setup and literally even fail in others, being an extremal case of near null cross section. (Like a capacitor turned inside out, some amps will oscillate without a correction circuit)

Since the mentioned near-null cross section foil-type speaker cables are succesful and praised products, apparently have no trouble driving high amperages, I am left to wonder why we bother with cross sectional area at all instead of simply focusing on geometry, metallurgy and dielectrics?

Also, is it actually skin effect in itself that even has much impact on SQ with designs made to eliminate it, or rather the well thought out general structure and LCR characteristics that come with such geometries? How could it possibly be audible, isn’t it more of an issue in radio applications? I do have hollow cables myself, which I enjoy, but I trust their strength isn’t in skin effect elimination because they still have enough outer radial gauge that I doubt very HF signal has much of an easier path, feels more like saving silver. But what do I know.

Seriously, is there actually global confusion on this subject, despite the precise mathematics we have to evaluate it?

If we do well with speaker cables with nearly null cross sectional area (foil), why is there consensus for the need for high gauge wiring? Is it very application specific or what?
I’d like to understand why ultra-thin foil is capable of transferring high amperages and what are its weak aspects?
A straight comparison of, say, a Goertz foil ribbon and ICONOCLAST cables would be very interesting.

Seriously, isn’t this a simple matter? I’m waiting for a mathematical explanation - me, personally, I have no clue how to approach this with other than common sense.
Well, common sense has carried me far enough to demand an answer to things like this. This is seriously bugging my brain!

Since I use integrated units on both my systems only speaker cables are relevant for me. In 6 years, for runs < 2m, I switched from legacy 1.5mm2 generic copper cable to 2.5mm2, and finally to 4mm2 (which was also used when I set up my desktop system). At no time did I perceive any change in sound quality. The ‘upgrades’ were purely cosmetic, since I like the look of chunky cables!

There is no confusion at all. Thin foils are designed to represent low inductance with decreased loop area, and ignore capactance, doing it. Just look at the data. The design is suitable for systems that can tolerate higher capacitance. Loop are is loop area, don’t get confused, the physics doesn’t.

The frequency dependant nature of the foil is the same as a round wire. Make it thicker, and the frequency high enough and the current moves to the surface as the self inductance of the “wire” increases in the center on out. The center of the wire looks higher and higher in impedance to to higher and higher frequencies.

This ignore proximity effect in high current cables (speaker cables) where the magnetic fields either push apart (same direction of current in two close wires) or pull together (opposite current direction in two close wires) the current dennsity. This alters the wire efficiency as the cross section is not used unifoirmly.

Audio is pretty deep skin penetration even at 20 kHz, about 18-mil. The current is only 37% what it is on the surface of the wire with the definition of “one” skin depth. Go two full skin depths and it is 37% less that where it left off from the first skin depth, or 0.37 *0.37 and so fourth.

A wide thick foil exhibits skin depth same as any wire, until you get to the ends where the sharp corners are a real EM field problem as they are decidedly different orientation than the fields along the width of the flat wire, making EM field management and cancellation technology far harder.

Flat wire reach good “L” by SPACING, and NOT secondary field cancellation. Same as round wires closer and closer together. It is just easier to use EM field cancellation in a symmetrical EM field around a round wire.

Just go look at the EM field line illuistrations on various shapes.

Most of audio is diffusion coupled, essentially the same current through the wire cross section, and this is what causes the non-linear issues with frequency. Add that to a non-linear Vp at frequency through audio and we have a pretty poor communication line compared to DC or RF.

The Vp at DC is ZEREO by definition. As we go down in frequency Xc goes way, way up. Xc is capacitive reactance and it simply describes the ability of a capacitor to easily move an AC signal at a specific frequency. Capacitors have a harder time of it at lower frequencies. This is why so much attention is paid to low frequency capacitors (audio is all really pretty low frequency) and how they work.

You would think as frequency rises and Xc decreases, that a wire would be more efficient with rising frequency but, internal inductance goes up with frequency (the opposite direction again!) and kind of trashes that idea.

Cable parameters have several things that go counter to one another and have to be weighed. What do I want more of, less of, the same balance of? How do I even DO what I want to do? Calculating it is one thing, but getting a cable to do it is vastly different. Math won’t tell you, past simpler symmetrical geometric designs, what is going to happen. The EM geometry to balance strand R, L, C, Vp, skin effect, proximity effect and bulk DCR to name a few is a hidden variable you need to ferret out yourself.

A foil has no magic to move current, it needs DCR and CMA same as any shape wire. Make it thinner just means it has to be wider to reach the same total CMA area for the current drawn (same voltage drop across the cable verses a load).

We all think in isolation on cable parameters when they work all at once. We decide today it is one thing and tomorrow another thing. You can’t do that. Cable is a system of attributes that push and pull every other one in a given design. I just chose to try to better balance ALL attributes and understand how they inter-relate to one another. This is all real stuff.

The harder issue is in a “network” between an amp and a load, how much CHANGE can we hear? This should ALWAYS BE the debate as cable measurements SHOULD BE made and designed in properly. It can’t sound better if it can’t measure and calculate better.

There is no sense in doing testing when the starting point of two cables isn’t even known to be accurate and correct. Once we know the cable is better, we can see if it is applicable in use. No two amp/speaker networks are the same. Amps linearity varies into reactance and speakers are natoriously non-linearly reactive. Add the cable for some more reactance.

ICONOCLAST simply uses the accepted physics to make better, although far harder and more expensive, cable designs to evaluate. We explain what and why we did what we did. We measure each assembly so you know it was done. Does it help? At least you know the starting point is really different, and correctly specified.

Any one variable by itself look too little to matter. Without listening, I agree.

Galen Gareis


Thank you for the learning experience yet again.
So have I understood correctly that since a foil’s area defines its amperage carrying capacity, we are generally always interested in the total area of conductors in any speaker cable, due to the current mainly travelling “close” to the surface since it has an easier path to travel along surface lattice due to increasing impedance towards the center?

I have hollow core cables with relatively little cross sectional area but more surface area than with conventional geometry because its individual bundles of thin conductors are braided, as in they overlap symmetrically and apparently this also reduces induction significantly compared to a twisted design?
So is it the braid-surface area and minimal depth at any section of my cables that mainly makes them sound so clear? They’d be 14 gauge were they not hollow, the air-filled core of hollow dielectric takes up a majority of them.
Is it so that capacitance is null in the hollow core?
Also, what could be the reason why their oval shape is such in the cable pair run, that the ovals are not parallel in longitude but width? Isn’t the AC current bunching phenomenon better adressed by running ovals such that their longer sides are against each other, dispersing the bunching? How come having them in this arrangement isn’t even worse than parallel round cables, since there’s two “thin” sections of ovals close against each other? Does the overall geometry here eliminate the need to address current bunching? I doubt QED would make a big mistake here.

The inductance and capacitance explain the trade-off. Are the numbers achieved more efficiently than other ways? Is a design biased to R, L or C?

Hollow wire is more just wow than any real advantage at audio. Make a wire hollow and it can improve conductor efficiency at the frequency high…but you need to aggregate conductors, same as more small round wires, to achieve DCR and at a far higher cost (and fragility). Because I can do something, should I? Smaller round wires do the same thing easier, better, and far more durably. Everything a design needs to do has to be considered, not narrow focused aspects (hollow wire) that don’t address other design issues. How are those added variables benefitted with a given design choice? I said it earlier, ALL the aspects of a cable are what we hear so they all have to be managed somehow.

Nature enjoys simplicity. Always pay attention to that. The simpler the design at the same measured metrics is always the best.


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Is it true that a very low inductance foil cable is very good at transferring transients very pristinely?
Is inductance the ultimate enemy of delicate transients?

No, a signal is a voltage level (capacitance) and current (inductance) both. Cable types will vary the amount of each.

Either L or C in excess values can be a problem. L and C also creates time based distortion; ELI the ICE man. Voltage lead current in inductors. Current leads voltage in capacitors. This changes when work is done resistively, and it can do work ONLY when it is resistive. L and C store current and voltage.

To mitigate the voltage and current limitations each contribute, good control of L and C mitigate and lowers inductive and capacitive reactance. L and C are in the reactance equations with frequency. Reactance isn’t linear. Lower L and C improves the reactance transfer function of voltage and current with frequency.

We can’t dump all our hopes and prayers on a single variable. Maximizing just L or C with disregard for the other is pretty easy. Reducing BOTH is very hard.


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I use flat cables - Townsend Isolda. They’ve been around for decades, I think close to 40 years. Ultra low inductance and capacitance handled by a network.

They have the advantage that you can stick them under a rug without knowing they’re there and you can use different lengths.

I’ve never had any reason to doubt their efficacy.

Ribbon cables with polyester (Mylar®) films are essentially capacitors, and thus are supposed to have little inductance. Yes, a ribbon does indeed “remove” inductance but at the expense of thousands of pF capacitance across your amplifier. This is more an electrical component than a neutral “cable” that manages R, L and C.

Be careful using such extreme design “benchmark” cable types (either low L or C) as we are adding electrical components and not a “cable” per say. Modern cable design eclipses what earlier designs have tried to do, and at far more benign loading to amplifiers and speakers.

A zobel network is really a speaker mitigation circuit that smooths a driver’s low frequency impedance anomalies making the cross-over non-linearity smoother. Most speakers have an impedance rise on either side (ported speakers) of a driver above and below the resonant saddle frequency. Zobel circuits aren’t able to manage ultra high capacitance of a speaker lead. That’s not what they do.

Resistive load (less reactance) design speakers are best with ribbon cable over dynamic drivers (more reactance) and are better with high negative feedback amplifiers to manage overshoot caused by high capacitance loads.

ANY cable is NEVER 8-16 ohm through the audio band, it is electrically and physically impossible to do as Vp drop to ZERO at DC, where “AC impedance” is infinity. Using open-short low frequency impedance measurements ALL cable impedance will rise, significantly, in impedance below 1 kHz.


It is hard to justify adding tremendous capacitance across an amplifier in the name of “low inductance” as the result of the high capacitance can be far, far worse than the advantage of low inductance (let capacitance go any where it wants to). Ribbon cables are large capacitors…the specification data supplied says so. The nature of how amplifiers work suggest AVOIDING high capacitive loads. Designing low inductance AND low capacitance with low resistance is what a cable should try to do. This is better for ALL amp/speaker interfaces, ie no cable is the best cable.

Use them if you wish, there are better modern designs available that mitigate both L and C.
Q. How does capacitive loading affect op amp performance?
A. To put it simply, it can turn your amplifier into an oscillator. Here’s how:

Op amps have an inherent output resistance, Ro, which, in conjunction with a capacitive load, forms an additional pole in the amplifier’s transfer function. As the Bode plot shows, at each pole the amplitude slope becomes more negative by 20 dB/ decade. Notice how each pole adds as much as -90° of phase shift. We can view instability from either of two perspectives. Looking at amplitude response on the log plot,circuit instability occurs when the sum of open-loop gain and feedback attenuation is greater than unity. Similarly, looking at phase response, an op amp will tend to oscillate at a frequency where loop phase shift exceeds -180°, if this frequency is below the closed-loop bandwidth. The closed-loop bandwidth of a voltage-feedback op amp circuit is equal to the op amp’s bandwidth product (GBP, or unity-gain frequency), divided by the circuit’s closed loop gain (ACL).

Figure 1

Figure 2

Phase margin of an op amp circuit can be thought of as the amount of additional phase shift at the closed loop bandwidth required to make the circuit unstable (i.e., phase shift + phase margin = -180°). As phase margin approaches zero, the loop phase shift approaches -180° and the op amp circuit approaches instability. Typically, values of phase margin much less than 45° can cause problems such as “peaking” in frequency response, and overshoot or “ringing” in step response. In order to maintain conservative phase margin, the pole generated by capacitive loading should be at least a decade above the circuit’s closed loop bandwidth.When it is not, consider the possibility of instability.


One of your most interesting posts! Thanks!

Now to read it again. There is a lot there. :slight_smile:

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As soon as I can get my eyeballs to stop spinning in opposite directions, I’m going to read it again.
Agree with the Elkster. That was fun.


I found it took a number of reads. Cool stuff.


Such reading, everyone in this hobby should read that as many times as it takes to understand it.
Thank you very much for the thorough input mister Gareis! Glad to have made this thread.