So I was just reading this thread because I have always wondered about the cable debate. You guys seem to be talking about capacitance and inductance, and whether that has any effect. I'm not sure about that, but it seems to be that impedance would effect frequency response anyway. I studied physics at uni but its been a while. I've been trying to remember what I used to know to think about how impedance would effect frequency response. Here is what I got:
So, when you are dealing with DC, you can characterise the response of a component like a cable in terms of a constant quantity - resistance. For a cable, resistance will be a function of area, length and material, but for a given cable it will be a constant. This would have no effect on the signal transmitted: you merely increase the power of whatever is driving current through this component to compensate for the added series resistance that it presents.
But with AC everything is different. There is no constant quantity that can characterise a given cable like resistance. The closest thing is impedance. Impedance, like resistance is a function of area, length and material, but importantly it is also a function of frequency. The same cable presents a different load to different parts of the frequency spectrum. If I remember right, the reason for this is that AC signals don't travel "through" the cable in the way DC ones do. AC signals actually propagate along the surface of a wire, only penetrating a small way into its interior. The amount they penetrate is called the skin depth. Now skin depth IS a function of frequency. The upshot of this is that because some frequencies penetrate deeper into the wire, they experience a greater effective cross sectional area, and so a decreased impedance. So different frequencies will be attenuated differently as they travel down the wire, and the wire will change the signal.
The skin depth varies a lot for different materials (I think it is much greater for silver, which might explain why silver cables don't attenuate highs so much), and I don't think there is any straight forward relationship between frequency and skin depth. It would be complicated and possibly vary greatly between different cables.
This all sounds very plausible to me, and makes me very open to the idea of different cables changing the sound quite a lot (especially in the high frequencies, where the skin depth is much less). Can anyone comment on this explanation - have I got the science right?
Interested in this debate...