Speaker Cable Questions Answered by Galen Galeis
1. Is it better to run long cables (RCA or XLR) or long speaker runs?
It is better to keep the signal at the load end, and not on the cable itself. A speaker cable has many amps of current, and the current squared times resistance losses go up with the square of the current. This is why speaker cables are such heavy aggregate AWG size, to make the cable look invisible to the current relative to the 2-16 ohm load. If our speaker cable was twice the resistance of the load, most of the signal would be lost across the cable in a ratio between the two load values, with the higher DCR getting more voltage signal. In practice the speaker load is super small resistance, so the cable has to be REALLY small resistance to be ignored. We want the cable to go away as much as we can. We have huge currents in speaker cables, so limiting those currents is really hard. All we can do is attack RESISTANCE, and keep it very low.
An IC cable, on the other hand, see’s little current as it is terminated into an “infinity” load, 47 k-ohm or close to that. Voltage equals current times resistance and if we have “zero” current we drop little voltage across the cable, and the signal is all dropped across the higher resistive load (47 k-ohm resistor). Even with a puny IC signal wire we see little voltage across the cable as the load is the opposite a speaker cable, it is HUGE by comparison to the cable. The voltage drops across the load, not the cable in aratio between the two resistances.
RCA cable can add ground differential noise between the ends of a long run. There is no way around that. If we raise the ground one end to the other we will get current to a lower potential ground point, and noise. The challenge is to keep the RCA shield as low a DCR as possible so any current in the shield times the shields resistance is a very small voltage across the cable. XLR are balanced, and the ground is floating so it is immune from those ground issue, and, any noise that is common to all the wires in the XLR cable are removed, by superposition theory. Equal voltages subtract to zero. Differential voltages add, our signal, add. XLR are superior for long runs.
2. Do cables degrade with time? If so, what’s the recommendation time-wise for when they should be replaced?
The degradation is in the plastics mostly. The light molecular weight plastisizers can migrate off and change the dielectric properties in LONG time frames. Like twenty years. Most cables made with PE, PP of FEP have anti-oxidation packages that pretty much stop what is called “migration”. FEP is good for about ever, and why it is an environmental hazard and should be properly re-cycled.
Oxygen can diffuse through some plastics if the “holes” in the plastic are larger than a oxygen molecule, same as a balloon losing the helium inside over time. This is a SLOW process as it is at ambient pressure and moderate heats, 20C or so. So this is a decades long thing or more. I’ve stripped back RG62 hollow core coaxial cables that are two feet long (production QA samples) and the copper was as bright and shiny as the day I made the cable 35 years ago.
Connections on the cable are permanent gas tight seals with crimp, sonic weld or solder. You can break them, but other than that you’re good to go about forever. The outer jacket of your cables is what will get beat-up with UV and age. I use FEP to keep UV from degrading the cable in sunlight in your living room. It should outlast you juyst sitting there.
Unless you get water inside your cables, they should work well for decades. It is easy to quick compare contrast with new cables and see if huge differences are heard. Adds are it is just a better modern cable than anything wrong with your older one. If you fire your old cable and take it apart what do you see? Are the plastics hard and cracking? Is the copper green and ugly? Are the connections high DCR and broken or corroded?
3. Copper, Silver, or a combination of the two? Or other?
If we use the properties of a metal, we can optimize the known attributes such as resistance, skin depth penetration, resistivity and grain structure formed in manufacture. There will be a specific change with base metals in calculation and the changes in a design to “normalize” to a new metal. But, It is a mystery as to why the copper does impact the sound as it does. It changes the electromagnetic field, as that’s what we here, of course, so something is superimposing onto the final field to alter it’s time based voltage level and again the EM wave’s amplitude fluctuations in time are what we hear as our signal. The final EM wave is a supposition of all the moving electrons in a wire. Since the electrons flow is through the wire’s cross section, they create distance based magnitude that vary. The EM wave is a DISTANCE squared based property so distance matters. WHY a copper or other metal’s structure changes the final EM voltage is not really understood. We have no repeatable calculations or empirical measurements to model what is happening.
Using multiple metals is tricky to do. I used a silver coated wire to investigate lead free silver solder adhesion and workability, first. The Beta testers all said this structure sounds better I said ????. So I tried it and yes, it does have a different sound. Why? The silver is 40 micro-inches thick, far too thin to effect any frequency except the very, very top harmonics of music. The highest fundamental is around 960 kHz or so, not even 10 kHz. The sound must be effecting the harmonics, not the fundamental as 10 kHz is too deep into the wire to really be changed much by the silver (so it is said an calculation and examination of the numbers). I can only hear to maybe 13 kHz, I’m 63 after all. What are we hearing? I can’t tell you WHY we hear it, we just accept it as an improvement, or not. As it was felt to be superior, I use this copper myself, we kept it as an alternative wire material structure.
The solution is to offer the SPTPC as an alternative to the TPC and three coppers, TPC, OFE and UP OCC in the interconnect. Make the copper’s structure and materials completely transparent to the design so we can tell if it is worth the price difference to buy.