Exotic Materials and Cable Construction
It's not too hard to understand why a lot of discussion of quality cables focuses on the materials used in cable construction. Just as with any physical product, the materials cables are made out of influence their performance characteristics, and so people want to know that the cables they're buying are made from the best possible materials.
Many high-priced cables are made with materials for which special claims of high performance are made. The most common among these are silver instead of or in addition to copper, "oxygen-free" copper, and Teflon. We'll address each of these in turn and explain what they are, what their characteristics are, and whether they make sense for particular applications.
Initially, it's perhaps helpful to point out that professional cables of the highest quality are routinely made without resort to any strange, exotic or expensive materials. If you look inside a typical audio or video production facility, you won't find it wired with silver-plated cables, oxygen-free copper cables, or (except, as we'll explain, in limited circumstances) Teflon-insulated cables. Broadcast studio engineers--people whose livelihood depends on the signal getting through with the lowest possible distortion and losses--rely on cables from companies like Belden and Canare, made with ordinary high-quality materials. People who spend millions of dollars on high-definition studio gear rely on these cables not because they're out to save a buck at the cost of quality, but because they are looking for the best possible product.
Let's take a look at some of these materials and consider how they bear on quality cable construction.Broadcast-quality cables are generally made with copper conductors; but it's not uncommon, in the consumer a/v market, to run into cables made with silver, or silver-plated copper, conductors. Why is this?
There is one respect in which silver is a better material for cable construction than copper: it is slightly (about 5%) less resistive (that is, more conductive) than annealed copper. "Resistance" is the property of any material which causes some of the electricity that flows through it to be converted into heat, and it's fair to say that resistance, in cables, is a bad thing--the less the better. All else being equal, lower resistance ought to be a good thing, and therefore one might think that silver would make for a better cable than copper.
That would indeed be so, but there are some other factors to take into account. First, the resistive loss in high-quality copper cables is already extremely small, because copper, though marginally less conductive than silver, is an extremely conductive metal. For example, Belden 1694A's center conductor resistance is 6.4 ohms per thousand feet. In a very long home theater run of 50 feet, then, the resistance of the conductor is 0.32 ohms, representing a minuscule cause of signal loss in a 75 ohm impedance video circuit; a solid silver conductor would drop this resistance by about five percent, resulting in a truly infinitesimal improvement.
This infinitesimal improvement might be worth something under extreme circumstances, all else being equal--but all else is rarely equal. First, silver is a more brittle material than copper, compromising the cable's flex-life. To solve this problem, silver is often plated over a copper wire--diminishing the conductivity benefit. Second, the conductivity benefit, as often as not, is offset by a reduction in wire gauge. Going from an 18 AWG conductor to a 20 AWG conductor, for example, results in an increase in resistance of over 50%; this swamps the conductivity benefit of silver, so that an 18 AWG copper conductor is more conductive, not less, than a 20 AWG silver or silver-plated conductor. When the comparison is between full-sized copper cables and silver-plated mini-coax of tiny gauge, like those one sees in many popular silver cable products, there's no contest; full-sized copper cables are dramatically more conductive, silver or no silver.
Think about it. The cables of the earphones are basic thin copper. Just sayin' 
Not that there is or isn't a difference, but they don't use silver cables in their design testing.
