Foil ribbon cables & skin effect

Cables
41

Arenith,

Proximity effect is current. Like inductance the dielectric doesn’t matter for proximity effect, the geometry does. The common language is available from many, many sources. This isn’t new stuff, any of it. GOOGLE it and read away.

Cable is always going to be a balance of properties. L and C make sure if that and both induce time based distortions we hear over amplitude attenuation distortion. More of a bad thing isn’t better. How L and C are balanced can improve what we hear; Vp linearity, current efficiency / coherence, phase (inductance) etc.

42

All cable designers need to change attributes to balance what they believe is the best compromise. Cables are a geometry problem and “age” doesn’t really matter. Longer doesn’t make it better or change it. Cable is agnostic to politics of the crowd.

Physics is physics. A ribbon has varying magnetic field around each wire as the surrounding material changes towards the ends and into the middle of the ribbon. It is just the way it is. Take a “simple” ribbon. Two wire parallel. Move them apart. The L and C change based on distance. A ribbon also has this built-in to the geometry as the wires are farther apart through the design. It is what it is. EM fields aren’t the same in the two ends or the middle based on material geometry.

Using a ribbon can alter other variables the designer feels are important. There are many who use ribbons, but that doesn’t remove what the reactive balance can be or the issues all cable faces. Knowing this won’t change how you enjoy your cables, either, it just better tells you how they really work.

If you use accepted open and short impedance measuring methods for low frequency cables, ALL cables see a large rise in impedance as you go lower in frequency. There are no exceptions.

Vp drops significantly towards 10% and even lessons at 20 Hz. Capacitive reactance rises significantly. Xc reaching infinity at DC after all. DC is blocked by a capacitor. Both properties increase the cable AC impedance orders of magnitude at low frequency.

Both Vp and C are in the numerator of the equation(s) for impedance. When one or both they go down, impedance fundamentally goes up and the opposite as one or both go up.

Cable look more and more like a resistor at RF where capacitance is less and less an issue as Xc drops lower and lower. C and F are in the numerator of the Xc equation; 1/(2piefC) lowering the reactance. This makes sense as a capacitor passes AC, the higher the frequency the better.

Impedance is loosely used to describe a real and imaginary AC resistance vector below RF and not a true RF impedance that has to obey wave theory of the signal. Audio can’t obey wave theory as the signal is too long to “fit” inside a length of used cable. Our beloved audio cables are not transmission lines.

No audio cable is even remotely close to eight-ohms. There is nothing wrong with saying so as again, it is what it is. No audio cable has Vp much above about 50% at best as it drops from RF values with lower frequency and is not linear. Vp will be well below RF values starting as high as 20 KHz and drop lower from there.

We need to use proper methods and stick with the facts on how cables work and test. Once we get the measurements right, we can argue over what attributes we can hear, or not. Cable won’t get better inventing the physical measurements.

We test speakers and amplifiers to set test methods and this in no way prevents a large number of nice speakers and amplifiers from being designed. Truth in measurement is not a restriction to design.

If you would like the data on all this, just ask.
galen.gareis@iconoclastcable.com

My cables are stuck with the physics same as any other.

2 Likes
43

Galen - it sounds from this as if you are talking about a cable with a flat arrangement of multiple strands, like some of the Nordost cables. I think what is being referred to here is a single, thin ribbon encased in some sort of plastic:

44

Yes, correct bad beef, flat arrangement of parallel wires. Goetz and others use rectangular thin sheets of copper with a dielectric between them to get low inductance (distance property) but higher capacitance (parallel plate area property).

Inductance needs field cancellation and close proximity to reach best in class inductance AND lower capacitance. Again, it is what it is.

Get inductance low with spacing, get it lower with field cancellation. Using field cancellation can allow a LARGER loop area to LOWER capacitance, too, for a given inductance. So the proper geometry allows some flexibility in design. You can leverage the inductive geometry improvement to lower L or C or a little of both. Again, the designer gets a good say in what is done…but WHY it works is the physics for everyone. We don’t get to make it up.

The user needs to be careful to make sure amplifiers tolerate the high capacitance well (feedback). For bi-wire the capacitance to the amp doubles, and inductance halves so be careful there, too. You may be able to use ONE set of leads but not two.

I chose an EM field cancellation design that mitigates excessively low or high L and C while making sure every wire looks exactly the same from an EM field perspective between polarities and ground. All those wires are the same electrical “cable”. To do that, every wire has to see the same dielectric along the way no matter what. One bonded pair in air is 0.126 uH/foot inductance but drops to 0.08uH/foot in a cable structure. Logically, capacitance goes up from 12.5pF/foot to 45 pF/foot to lower inductance so much. Capacitance would be far higher with no field cancellation. I can’t escape reality. I chose the dielectric wall to set capacitance as high as I feel is safe for bi-wire, as well as single wire set-ups. Too thin wall, is also too unsafe. We have practical considerations!

Based on the equations higher capacitance improves Vp linearity at the higher frequencies (lowers it some to better match the lower frequencies). Lower inductance lowers phase response in the audio frequency range. So that’s why I went the direction I did. Resistance also is in the Vp low frequency equation, so this drives the need for higher resistance small wires in parallel. But, that also drives capacitance up as we increase the parallel plate are between all those wires! Again, I get the same physics everyone else does.

I’m not thrilled with damaging someone’s amplifier with high reactance designs. We’ve been there before. Many amps are OK with reactance, but aren’t as linear when driving reactive loads. This is why amps sound so different speaker to speaker (that includes the cable as part of the speaker).

We don’t have a consistent test for amps into reactive loads, just a big old resistor. Some sort of standard reactance test would go a long way to help isolate what amps do what and why. Tubes, SS and Class D SS all drive reactance differently.

Not being afraid to properly characterize components will go a long way to allowing customers to pick what works best for them. This isn’t a best and worst issue, it is a method to allow CHOICE.

Best,
Galen Gareis

45

All I was saying was that I am one of many people using ribbon cables, many people have been using them for decades, you don’t really see anything in the audio press about products that have been selling happily for 40 years. I regret that I know nothing of physics or electronics so I didn’t get past your first paragraph.

46

Isn’t this quite what we want?
Unless we have an amplifier that doesn’t handle higher capacitive loads, high freq oscillation…
Is high capacitance any problem in a cable if we have an amplifier circuit that doesn’t care about a caacitive load cable?

47

But we don’t have that situation where reactance isn’t important. We are adding the cable’s reactance to a pretty awful load, the speaker, that is highly reactive in most cases. There are a few speakers that are more resistive, yes. The amp sees the cable and speaker as one load.

Second, where is the data to show how linear an amplifier is into various reactances? We don’t have that, only the resistive load RMS test. Same as cable, the ability of an amplifier to be linear into reactive loads is what we hear. Not saying it is better or worse, but it will change the signal.

There are cable’s that throw L or C to the wind and build a long capacitor or an inductor. Either of those isn’t hard to do, but what does that do to the time based cable error? I chose not to do that. Getting both low is difficult but offers advantages across all speakers and amplifiers. If we can get the cable to “nothing” we just have the speaker and amplifier.

We do have cable, so deciding how to balance the time based error for voltage and current is the best we can do. our ears hear time over attenuation and is why amp/cable/speaker combinations are all so different sounding.

Being devil’s advocate, the LENGTH of the cable suggest that the time it takes to ALTER the time based input to output is so small as to be insignificant. The calculations do suggest this and there is no doubt about it looking at the numbers. We are, after all, still moving at 10% or more the speed of an EM wave in a vacuum…pretty darn fast. There isn’t much time for all this to happen, right?

We have what all the numbers are, and we have how the amp/cable/speaker are, too. There are differences that better cable technically should not be, on a one on one attribute bases, really changing…the numbers say so.

I’ve worked it out to what I feel is the most audible attribute and concentrated on linearizing that but with low L and C. The designs needed to truly do that, arrive at decent L and C and R with good time based properties, isn’t easy at all. Stuff gets very complex pretty quick. The improvements also get stiffer and stiffer to truthfully reach.

Will I ever mathematically calculate the EM field’s final inductance in the speaker cable? Not a chance! But I can measure it’s value from a single bonded pair @ 0.126 uH/foot and the final cable at 0.08 uH/foot. It works. How well we could model it is REALLY complex as we have a flat oval shape with 48 wires!

Better has to be achievable if a cable is to every sound better. This we know, too. My experiences has shown cable with poor fundamental’s don’t sound as good so the foundation of the cable’s factually known attributes is very important. And yes, this has as much to do with how it affects your amplifier driving the speaker as “just” the cable. You can’t really hear just the cable.

Best,
Galen