If you have a speaker switch (pass through A/B) that did not add distortion had 2 sets of the same speaker, and your 2 wires for comparison from the same source. A listening test may work but would still be subjective to many.
I am sure people will find fault in this method and will only work if you have 2 sets of the same speakers in the same operating condition.
Or go buy some sound analysis software to take a stab at determining what cable or wire will work for you.
You really need to control the variables to make any real determination and remove well guessing.
Have a great day.
I Robot