Regarding differences in cable propagation velocity as a function of frequency, the following paper (which I and another member had referenced in posts here a few years ago) appears to me to be credible as well as informative:
http://www.audiosystemsgroup.com/TransLines-LowFreq.pdf
See Figure 2 of that paper, although it addresses a coaxial cable rather than speaker cables. It can be seen that propagation velocity does decrease considerably at low audio frequencies compared to high audio frequencies. However, even at 20 Hz the propagation velocity, while much slower than at higher frequencies, is still about 5,000,000 meters per second, easily fast enough to be utterly inconsequential in the context of a home audio system, despite claims in some marketing literature to the contrary.
As Ralph aptly said in another context here not long ago, where there is an effect there is snake oil for it. I would add that is particularly likely to be true when the claimed effect is not or cannot be looked at in a quantitative manner.
I believe that this statement is correct, and is unrelated to skin effect. Cable propagation velocities are usually somewhere between around 50% and 95% or so of the speed of light in a vacuum, and are dependent on the dielectric constant of the insulating material surrounding the conductors. Numerous references can be found on the web in support of that.
The reason is that signal energy is conveyed in the form of an electromagnetic wave (rather than by the associated but vastly slower "drift velocity" of electrons), and for the most part that wave propagates outside of the conductors, within the dielectric (aside from a small fraction of that energy that is absorbed by the resistance of the cable itself).
Again, though, whether an audio signal propagates from one end of an audio cable to another at 1 nanosecond per foot (close to the speed of light in a vacuum) or at 2 nanoseconds per foot, or somewhere in between, is utterly inconsequential. And if a 1 ns/foot cable sounds different than a 2 ns/foot cable, the reason is something else.
Regards,
-- Al
http://www.audiosystemsgroup.com/TransLines-LowFreq.pdf
See Figure 2 of that paper, although it addresses a coaxial cable rather than speaker cables. It can be seen that propagation velocity does decrease considerably at low audio frequencies compared to high audio frequencies. However, even at 20 Hz the propagation velocity, while much slower than at higher frequencies, is still about 5,000,000 meters per second, easily fast enough to be utterly inconsequential in the context of a home audio system, despite claims in some marketing literature to the contrary.
As Ralph aptly said in another context here not long ago, where there is an effect there is snake oil for it. I would add that is particularly likely to be true when the claimed effect is not or cannot be looked at in a quantitative manner.
... the velocity of propagation of the signal (versus the velocity of the actual electrons) is determined by the dielectric or insulation material that the electromagnetic wave is predominantly traveling through.
I believe that this statement is correct, and is unrelated to skin effect. Cable propagation velocities are usually somewhere between around 50% and 95% or so of the speed of light in a vacuum, and are dependent on the dielectric constant of the insulating material surrounding the conductors. Numerous references can be found on the web in support of that.
The reason is that signal energy is conveyed in the form of an electromagnetic wave (rather than by the associated but vastly slower "drift velocity" of electrons), and for the most part that wave propagates outside of the conductors, within the dielectric (aside from a small fraction of that energy that is absorbed by the resistance of the cable itself).
Again, though, whether an audio signal propagates from one end of an audio cable to another at 1 nanosecond per foot (close to the speed of light in a vacuum) or at 2 nanoseconds per foot, or somewhere in between, is utterly inconsequential. And if a 1 ns/foot cable sounds different than a 2 ns/foot cable, the reason is something else.
Regards,
-- Al