Nordost SuperFlatLine Speaker Cable Review

[Julf]

What is "velocity of propagation"? Why is it 91% and not 100%? And how would you measure this?

Ratio of signal propagation speed to speed of light. Usually only relevant for RF frequencies and impedance-matched transmission lines.

 

[theREALdotnet]

What is "velocity of propagation"? Why is it 91% and not 100%? And how would you measure this?

The speed of light depends much on the medium the electromagnetic wave is travelling in. Only in vacuum is the speed of light equal to c.
https://en.wikipedia.org/wiki/Velocity_factor

EDIT: As for measuring it, Alan Wolke has a cool video about measuring the length of a cable with just a 9V battery, a resistor and an oscilloscope, given the velocity factor of the cable. In the same fashion you can measure the velocity factor, given the length of the cable.