It's Simple

Only the R (resistance) matters at audio frequencies (20 hz - 20 kHz). Thinner wire has more R - thicker wire has less R.  The L (inductance) and C (capacitance) of typical speaker wire are of too low a value to affect a music signal. Physics 101!

Physics 101?  Inductive reactance of 10ft (20ft both ways) gauge 14 cable at 20kHz is about 1 ohm.  Resistance of this cable is 0.05 ohm.

My co-worker always buys Sutter Home wine @$4 a bottle.  He says he cannot tell the difference between wines.  He doesn't say there is no difference.

+1 Shadorne

Ieales, Let’s imagine 0.1 ohm (both ways) cable connected to 8 ohm speaker that has lowest impedance of 4 ohm. At 4 ohm we have divider of about 1/40 equal to -32dB while at 8 ohm we have 1/80= -38dB. Do you think that 6dB difference in audible area won’t make any difference?

You might be right that cable R can be ignored only for the purpose of damping factor, since there is always speaker’s own impedance in series with back EMF force (and 2/3 of it is resistive), but one can argue that capacitance and inductance are not that important either. Almarg pointed out that speaker, having inductive character most of the time, has very high impedance at high frequencies (where cable inductive reactance can go as high as 1 ohm) while capacitance plays very small role because of low output impedance. As for the skin effect, that you mentioned - it starts at about gauge 18 with copper at 20kHz. Our ears are not very sensitive to volume change but are very sensitive to frequency smear. When you change loudness by 1 dB nobody will be able to detect it but when you adjust treble by +1dB you can detect it easily. In order to provide low resistance without frequency smearing companies split wires into multiple strands. It won’t help much as long as the strands are in magnetic field of each other (skin effect exists). To improve it cable designers place conductors on hollow tube (or flat cable pattern) reducing magnetic field to one that comes only from neighboring wires.

Ieales, thank you for correction. I assumed gauge 17 (worst case) that is 0.1 ohm for total of 20ft, but calculated it wrong. The difference in level between 4 and 8 ohm speaker is 0.1dB. That’s most likely inaudible.

Al, I should've known better.  I calculate dividers almost every day, but yesterday was my "slow" day.  On positive note, I didn't make any bank transactions  :)