If Cables Are Not Tone Controls...

@chayro

You accomplish this by listening. Listen for the differences between recordings, and even from track to track on the same recording. The more similar all the tracks sound, the more the cable or component is imposing its own "sound" on the music, and thus the less transparency. Conversely, the more differences you are able to hear, the less the cable or component is overlaying its own sound (often referenced as ‘house’ sound of a component or cable) and the more transparent it is to the source material.

In your example above, you said ‘I have a pair of speakers that I did not like, but were transformed with different speaker cables’. I think what has happened here is second set of cables took away a ‘bad thing’ like harshness or something else you were hearing with first set of cables. In this case a cable change led to more transparency. Now you are hearing a sound (mind you from same components) is more like it should be :-)

Nothing in home audio is transparent.  Everything affects how a system sounds, including internal wiring and external cables.  It is the degree of impact and significance resulting from those differences, as well as the cost, that seems to be most often debated here.  To your original point, I agree with you, people can't have it both ways....those who hear differences between different cables and then use those cables to adjust the sound of their system to their liking are using cables as a form of non-adjustable tone control.  

Tone control implies just that. I don't consider buying another pair of cables and installing them a convenient form of control. Once you go down that line of thinking, you might as well consider your amp as a 'tone control', as well.

Never had this problem as i use PURIST NEPTUNE and DOMINUS cables which are great sounding  and not colored.

I am using Purist cables as well. They sound wonderful in my system. Or should I say, the system sounds wonderful with the Purist cables. Am I using them as tone controls?  Couldn't say.