Does cable geometry (twisting conductors) affect inductive reactance?
Yes, it will be lower but not zero because the centers of the conductors would have to occupy exactly the same space. Typically, the inductive reactance will be reduced. It depends upon how close the wires are physically.
The closer the wires to each other, the higher the capacitance. The twisted speaker cable is much larger than having the +/- wires separated. If global negative feedback is involved, the feedback signal will be phase shifted, distortion will rise as the frequency rises. How much is dependent upon the amp design. Could be very little, or somewhat.
What affect does inductive reactance have on signal passing through the cable?
Think of a voltage divider. The higher the inductive reactance of the speaker cable, the lower the signal voltage is to the speaker driver. Of course, phase relationships are also involved.
One thing in our favor is that usually the driver impedance rises along with the speaker cable inductance. Still from my testing, the results are noticeable.
I just reduced my parallel speaker cables from 10 parallel 18 gauge wires to 8 parallel 18 gauge wires. There was a difference.
From a DC resistance stand point, the gauge was reduced from approximately 8 total gauge to 9 total gauge.
From my above post, inductive reatance....
1 length of 18 gauge solid straight wire, 6 feet long, at 20khz, has an inductive reactance of approximately 0,368 ohms.
1 length of 14 gauge solid straight wire, 6 feet long, at 20khz, has an inductive reactance of approx. 0,3472 ohms.
1 length of 8 gauge solid straight wire, 6 feet long, at 20khz,
has an inductive reactance of approx. 0,3155 ohms.
8 parallel speaker wires, inductance is only 0,046 ohms inductive reactance at 20khz. It is more like a direct connection to the amplifier (assuming no xover). And very little, if any cable capacitance if the +/- wires are separated.
Cheers
Steve