Are cables additive or subtractive?

@jasonbourne52 - My experience aligns with yours and the box somewhat because I find that differences are very small when switching back and forth. I find the biggest difference when I’ve made a change in my system after listening to it for months. In this scenario, some changes become very obvious to me while others don’t.  It’s not possible to use any system other than your own as a point of reference in my opinion when evaluating things like cables. 
 

Example: I struggled to really describe any difference between AQ Sydney RCA and Monoprice XLR in my current setup, but the move to Morrow Audio MA4 was clear and obvious to me. 

I should also say this, I've wondered if sometimes a maker's mid-range cables weren't deliberately made to be darker?  Like I've felt that they make low and mid-range cables to demonstrate an obvious difference, but only because the high end cables didn't totally suck?

I should also say this, I've wondered if sometimes a maker's mid-range cables weren't deliberately made to be darker?  Like I've felt that they make low and mid-range cables to demonstrate an obvious difference, but only because the high end cables didn't totally suck?

Not for evil intent necessarily. The darker cables can be a godsend for a too bright component. Nothing wrong with getting a little help until one is ready to make an upgrade.

@jtcf 

Might as well hang a sock over your tweeter. Cables as tone control? So NOT!

Another way to ask the original questions is:

How can a cable add anything to the electrical signal?

The scientifically perfect cable would pass the signal unaltered.

Every cable changes the signal.

Here's an over simplified example:

If cable A has a better high end than cable B then either cable B is rolling off the highs (subtractive) in comparison OR cable A is rolling off the lows (subtractive) making the highs more prominent in the overall sound.