03-17-13: GregmI'll second that. Your writeups make a great many excellent and important points. Well done!
Rower30: your original post & further "articles" are very interesting and, if i may say so, a significant contribution to the community.
The one area I would question, though, at least with respect to situations where the wire is not plated, is your emphasis on the importance of minimizing skin effect.
Audio has a skin depth of 18-mils. This is where the current in the wire center is 37% of that on the surface. The current gradients can be vastly improved with smaller wire (current closer to the same everywhere).First, I would rephrase the second sentence to say that "this is where the current in the wire center is 37% of the TOTAL current, the other 63% flowing in the part of the wire's cross-section that is between the surface and the skin depth."
As you undoubtedly realize, with respect to sub-RF frequencies what skin effect basically does is to increase the resistance of the cable as frequency increases. It can be calculated that under typical circumstances (e.g., cable lengths on the order of 10 feet or so, and used with dynamic speakers, which generally have impedances that are high in the upper treble region and above), the effects of that resistance rise will be a rolloff at 20 kHz of a very small fraction of 1 db. That is likely to be completely swamped by room effects, speaker inaccuracies, inaccuracies elsewhere in the system, and the high frequency rolloff and finite resolution of the listener's hearing.
I can provide such a calculation, if desired.
On the other hand, in the less common situation where the length of the speaker cables is particularly long AND the impedance of the speakers descends to very low values (e.g. 1 ohm) at 20 kHz, as it does in the case of many electrostatics, I would agree that skin effect might conceivably become a marginally perceptible factor. And as you indicated, additional considerations come into play in the case of plated wire.
Also, a minor correction to a statement in your initial post, which was most likely just an oversight. 16 ns is 16 billionths of a second, not trillionths.
Again, though, my compliments on what IMO are a great many excellent and important points that are made in your writeups.
Regards,
-- Al