Lplayer, thanks for providing the link to that paper, which is excellent IMO.
When I wrote my earlier comments, I hadn't thought of the fact that propagation velocity will slow at low frequencies. However, as can be seen in Figure 2 of the paper, it will still be about 5,000,000 meters per second at 20Hz, meaning that propagation times through cables at that worst case frequency are still utterly insignificant in a home audio system.
For those who don't want to bother with all the technical stuff, IMO the bottom line of the paper is expressed in its last two sentences:
Thus, at audio frequencies, a cable less than 2,000 ft long is no more complicated than its series resistance and parallel capacitance. As the cable becomes longer, or as frequency increases, the cable will BEGIN to behave as a transmission line.
I would add that in a speaker cable, in particular, inductance can also sometimes have audibly significant effects. The focus of the paper is mainly on transmission of line-level signals through coaxial or balanced cables.
Regards,
-- Al