+1… all posts above.
As far as not hearing the difference. I think it need not come from hearing deficiency, but it is possible the person is not focused or interested in a (or a number of) particular aspect(s).
As an example from a different realm:
When my partner and I watch a movie… I might exclaim “look at that Monteblanc fountain pen”… and she will reply… “what pen? You are really observant.” Which may or may not be true, I am just observe different things. She may have observed the nuance of a dress that didn’t notice at all.
Anyway this is an attempt at understanding why some folks don’t seem to hear differences that are obvious to the rest of us. I probabably know 25 folks with extensive high end experience. We can swap a power cord or something and compare notes and make exactly the same observations… in great detail. One of these folks hardly ever hears the difference.
What I do not understand is why some folks that don’t hear anything and therefore adamantly call BS on it. If I am learning, I want to… well, learn and understand. So, I would be trying different things and reading, ask questions, and if I concluded I couldn’t hear a difference… I would just not read posts about wires, let alone join in. The reality is, by broadcasting “all this is BS”, you’re only broadcasting your own lack of understanding and overinflated ego.