Steve, Tom Nousaine published a very interesting article in Sound & Vision detailing the results of blind tests of speaker cables. He had audiophile listeners compare 16 AWG zip cord to their own chosen brand/model of speaker cable, in their own homes, on their own systems, with their own chosen playback source and media. He gave the listeners a choice between ABX switching and cable-swap (scored as same-different) methods (except the last listener; for her, he used both ABX and the cable-swap method because the others had chosen ABX). No time limits; in fact, he let the listeners warm up and practice so they would become as comfortable as possible with the tests. A minimum of 10 trials per listener. None of the listeners, despite their high opinions of their own hearing prowess, could correctly identify the cables they were listening to a statistically significant number of times: in comparing the zip cord to a set of T1 bi-wires, one listener guessed correctly 3 out of 10 times, which is within the likely range of results that would arise from just guessing or flipping a coin. Another listener's results were 4 out of 10; again, within the range of strictly chance.
In short, the listeners were asked to prove that they could indeed hear audible differences between the cables, and none succeeded.
Regarding ABX: Some may allege that rapid A-B switching "hides" real differences. That's one vague assertion! My opinion is to the contrary: it allows the closest thing to actual side-by-side comparison possible in audio. Obviously we can't listen to two things simultaneously and judge between them; the best we can do is put the same audio through both DUTs, match the levels, and freely switch between them as needed to make the comparison.
In short, the listeners were asked to prove that they could indeed hear audible differences between the cables, and none succeeded.
Regarding ABX: Some may allege that rapid A-B switching "hides" real differences. That's one vague assertion! My opinion is to the contrary: it allows the closest thing to actual side-by-side comparison possible in audio. Obviously we can't listen to two things simultaneously and judge between them; the best we can do is put the same audio through both DUTs, match the levels, and freely switch between them as needed to make the comparison.