"Supra PLY 3.4 Speaker Wire, 12 AWG, by the running foot. PLY wire is closely spaced, reducing inductance and loss at higher frequencies. Tin plated OFC copper wire, Ion stabilized Ice Blue PVC jacket."
Before considering more special "esoteric" 2nd and 3rd-order effects, such as conductor metallurgy, the performance of audio cables is principally determined by their series loop resistance (R), their series loop inductance (L) and their shunt capacitance (C). Both the absolute and the relative values of R, L & C matter. For speaker cables connecting high performance amplifiers to every day electrodynamic (moving coil or ribbon) speaker drive-units that are desired to operate with fidelity across the audio band, the R & L (cable resistance & inductance) must both be low, while the value of C (capacitance) does not matter much [1,2]. This is so because current flow into conventional speaker drive-units is relatively so much larger than in line-level connections, and also absolutely large, ranging to over 100 Amperes in some instances. This is especially true of auto (12 volt) installations. But simply using a fat wire gauge makes R low at the expense of increasing L. This is musically unacceptable for high sonic quality.
"Squaring the circle" techniques to make this loop inductance, L, low, simultaneous with low resistance, include tapes, either stacked in parallel pairs, or several arranged side-by-side in ribbons, where the ends are X-connected. But of course, these types are (i) impractical to fit to nearly every known speaker connector (at least without introducing discontinuities), (ii) are stressed and may be unsightly when right angle surface bends are required in domestic installation, and (iii) are unsuited to for mobile use by professionals. Litz techniques, i.e. multiple, parallel, insulated conductors are more practical in use and laying out, but when properly executed, they are expensive.
They are also awkward to terminate and must be soldered. Other types are grossly large, like industrial pneumatic pipes, making them unsuited to smaller domestic dwellings.
Conventionally, fat conductors" high loop inductance (which raises impedance at +6dB/octave) is further raised due to internal eddy currents causing "Skin effect". This acts like "the square root of an inductor", i.e. progressively adds a +3dB/octave component to the cable"s series inductance. With typical speaker cable runs of a few metres, the combined inductive effect is that performance in moderately heavy, plain conductors is measurably affected with steady signals at or a little above 1kHz. Whereas for music transients, even low bass qualities are affected.
Conventional stranded cables with copper, silver or related conductors suffer from complex oxidation. The surface becomes a semiconductor. The diodes so formed between the strands are not seen by steady-state signals, but look like the plates of a high value capacitor to transient signals. This causes low-level energy storage and release after transients, that is invisible to steady state testing yet nonetheless perfectly audible with many music recordings. This "transversal distortion" may also be described in terms of the TEM (Transverse Electro-Magnetic) Wave, which takes a direct route, whereas electron flow is "trapped" inside individual, particular strands that are commonly twisted away from the most direct route, at each of the inevitable bends in a stranded cable, when laid-out.
Supra Ply is able to be a large-section, low resistance cable, while also overcoming skin effect and transversal distortion, by using a proprietary, pure tin plating. This has the double benefit that tin and copper meld without forming a diodic barrier (as with many silver-plated copper "audiograde" conductors) and that tin strongly resists most common causes of metal corrosion, and hermetically protects the copper, making Supra Ply ideal for outdoor use.
By contrast, most audiograde cables claiming highly pure copper or silver conductors are either wholly unprotected from contamination, initially by the out-gassing of the plastic covering (even if PTFE/Teflon), and eventually from the impure atmosphere - and even from accidental immersion in liquids! Some very expensive cables are protected only by a very thin, initially good lacquer, that must eventually crack, invisibly, with handling and age.
Even if oxidation should form on the outside of Supra Ply, it will be sonically benign, as in audiograde "metal oxide" resistors - which are really tin oxide.
Ice Blue heat and aging resistant PVC jacket
3.4mm (12AWG) wire
2 conductor, 192 strands of 0.15mm wire
Tin plated OFC
External Size: 7.2mm x 7.2mm
5.1 ohm per kilometer (3280 ft)
0.2 microhenries per meter