It's true what you say. You would need to account for variables and test the best you could.All of this could be from a million things. Maybe you were hangry? Maybe you didn't sleep well?
I mean seriously.
A good example is my Klipsch speakers and the midrange/lower midrange between 80-200Hz. It just sounded thocky not tight and punchy. It didn't present itself in most songs, but enough to annoy me. I tried trimming it out, but then other songs sounded more dull. I also had some 8-10kHz harsh sounding highs that I could trim out, but it was still there in a matter of degree.
I saw a Youtube review that said with my Klipsch R51-M speakers, you need to pull them away from the wall about a foot or more and if you have the speakers toed in, to set them straight ahead, not toed in.
Problem completely solved. I'm enjoying these speakers more than I ever have. Recently, I was even considering buying another brand (with a technical review) just to see if that would solve my problem. Now, I'm not looking, at all. However, if I had the money, I would do it just because it is fun to sample things.