@Cakyol
If you perform some quantitative calculations regarding speaker cable capacitance, such as I describe below, I think you will conclude that what I said is correct.
The high frequency rolloff you refer to results from the low pass filter formed by the combination of the capacitance of the cable and the output impedance of whatever is driving the cable. The bandwidth of that filter, defined as the frequency at which 3 db of rolloff has occurred, is:
3 db bandwidth = 1/(2 x pi x R x C)
If R is specified in ohms and C in farads, the calculated frequency will be in Hz.
Since the output impedance of a power amplifier is very small, the resulting rolloff will occur at a frequency that is so high as to be totally insignificant in the case of an analog audio signal, under any reasonable circumstances.
For example, a 20 foot length of the cable the OP is considering has a total capacitance of 520 pf. The Kinki-Studio amp the OP is obtaining has a specified damping factor of 2000, so its output impedance is approximately 8/2000 = 0.004 ohms. But let’s assume a MUCH worse situation than that, say 2000 pf and 1 ohm. Even in that case , which is vastly more extreme than the OP’s, the 3 db bandwidth calculates to 79.6 MHz. In other words, it is high enough to be totally irrelevant to analog audio signals.
On the other hand, as I had mentioned, the inductance and resistance of a speaker cable might have some significance in certain situations, especially if the impedance of the speaker is very low at some frequencies.
In contrast, in the case of a line-level analog interconnect the fact that the cable may be driven in some cases via output impedances of hundreds or even thousands of ohms can sometimes result in the effect you referred to being significant. While in that case inductance and resistance are unlikely to be significant. The impedances presented by inductance ("inductive reactance") and resistance are presented in series with the input impedance of the destination component, and that input impedance is almost invariably vastly higher than the resistance and the inductive reactance of a line-level interconnect at relevant frequencies, even if the cable is particularly long.
It is also true, as I mentioned, that if a speaker cable has extremely high capacitance it can adversely affect the performance of the amplifier, depending in part on the gain, feedback, and bandwidth of the amp. Effects such as overshoot, ringing, oscillations, and on rare occasions even damage have been known to occur when some amps are used in conjunction with speaker cables having ultra-high capacitance.
Regards,
-- Al
