In general, the appropriate gauge for speaker cables is 12ga +/- 2-3gauges (about 10ga. through 14ga.)
This has been borne out by some "objective" tests that have been published in JAES and elsewhere. BUT...
But, that doesn't tell the whole story by any means.
Two cables that are identical in effective (electrical size) gauge may result in completely different sound. A cable made like a capacitor will have different sound than one made like a big coil (inductor).
The problem with really big (low gauge) wires is that they start to get self inductive and roll off the top end... while the problem with thin wires is that they tend to not be able to deliver peak currents.
Still, it is interesting to try some rather thin pure silver wires on your bi-amped tweeters and see how that sounds.
:- )
So, the 12ga turns out to be a good middle of the road compromise.
So, gauge is only the simplest criterion for speaker cables.
In abstract theory, the idea cable would be "none at all" - the output devices being part of the voice coil of the speakers, so no distance at all. The idea for the practical audio person is to use a speaker cable that comes as close as is possible to having no cable at all.
In reality, most cables are designed to, or by definition (do anyhow), in some way interact with the amp and the load to cause some change in sound. Thus, the hunt for a "good sounding cable."
What I call the "geometry" of the cable plays a big role in the gross L & C of the finished cable - and is a big reason that people hear a difference between "regular" and "shotgunned" speaker cables. The geometry being everything between the two conductors and how the conductors are physically related to each other.
One problem can occur like this: you might have actually tried a cable that is essentially "not there" and not liked it at all! It may have revealed another defect in the signal path. So often folks use cables to attempt to do what I call "complementary coloration" in an effort to get what we call "good sound." The problem with this quest is that it is rare or impossible to in effect filter something twice and restore the original (which is the ultimate goal for high end).
Anyhow, the gauge thing is only a minor consideration in the resulting sound that you're likely to hear.
Of course, you mileage may vary, as may your perceptions and ears...
_-_-bear
