Sean I realy love to see everything in numbers.
Let's take 20m of Alpha-core the high-capacitance wire or interconnect. Let's assume that such high-capacitance wire has 50pf/m(I think it's large enough) that will overall give a capacitance of 800pf and voice coil inductance of 0.3...0.7mH and determine a self-oscilation freequency of such load wich equals 1/sqare root of product of both.
Without precise calculation I'll state that in the denominator the number has a degree of -7.5 that states that self-oscilation may occur at tens of megahertz. These freequencies, if not filtered properly, may result a parasite oscilations of the amplifier that will act certainly negatively on normal amp performance. These freeququencies have also a large enough amplitudes so that it's lower freequency harmonics may also be amplified. The solution states in blocking such freequencies and limiting sencitivity for lower freequency harmonics to make the amplification or preamplification stable. If the amplifier was made tube or SS with carefull consideration of RF compatibility rules, wires are only to be considered as resistive load and should realy cost minimum. The best ones are only under zero-Kelvin temperature where super-conductivity effect was discovered.
You can also plug-in another reasonable values of capacitive and inductive reactance of speaker or speaker wire and all you realy need to know is simple radio equation where you equate both of the reactances to determin the self-oscilation freequency.
Every time you divide or multiply this derived freequency by 2 you get even-order harmonics and it means that you multiply the product of reactances to get a freequency divider. To get freequency multiplier you decrease reactances etc...etc...etc... Any harminics of self-oscilating freequency have smaller amplitude so by selecting a values of feedback resistor and capacitor you can always prevent amp's self-oscilations.
Please note that in tube amps output tube less-likely to oscillate by itself but small-signal ones realy do while in transistor amps both input and output transistors may oscillate at RF.
