What makes capacitance bad??

[DF96]

Originally Posted by Speedskater

But more correctly it's also the leakage resistance of the insulator (conductance) that makes the formula very messy at audio frequencies.

Yes, but in practice I think it turns out that at audio frequencies insulator conductance is negligible when compared to capacitive reactance, but conductor resistance dominates inductance.

[Speedskater]

Jim Brown has a good paper on Transmission Lines at Audio Frequencies:

http://www.audiosystemsgroup.com/TransLines-LowFreq.pdf

Dynaudio Ocos Loudspeaker Cable has very high insulator conductance:

http://www.dynaudio.com/eng/pdf/DYN_...Grundl_INT.pdf

A solution in search of a problem.

[Elvee]

Originally Posted by DF96

but conductor resistance dominates inductance.

That's debatable: a typical figure-of-eight speaker cable has a lineic resistance of ~15milliohm/m, and a lineic inductance of ~1µH/m.
At a frequency of 10KHz, this is equivalent to 62milliohm/m, 4 times the resistive part.

[DF96]

At 1kHz, assuming your figures, it would be 0.4 times the resistive part so in the LF-mid region where audio signals are strongest the resistance dominates. OK, I will qualify my statement: for most of the audio band resistance dominates. If you consider the audio band to have ten octaves, then only the top three(ish) have inductance dominating. My main point was that you have to consider inductance, resistance and capacitance but you can usually ignore insulator conductance.

[Elvee]

Originally Posted by DF96

but you can usually ignore insulator conductance.

I completely agree: all current polymers, including the humble PVC can be considered as perfect in this respect, and for this application.