So I did actually sit down and write out an email to my FIL, which did start an bit of a further dialogue on the subject. I think he got it. It remains to be seen if he'll take the time to sit down and listen, and whether or not it will mean anything beyond the effort to acknowledge his caring. Here's the main body of that email:
Please feel free to keep your own comments coming. I've enjoyed the input.
The primary motivator that drives audiophiles is to recreate the illusion of live music within a three dimensional space in their home. That is to hear the performance as if there were a stage in front of you with a singer at the center, drums in the back and to the left, a cello to the far right and mid-stage, a mouse scurrying across the wooden floor in the back of the hall stage right, etc. The ideal is the full illusion that the performers are there in front of you in a space that is is not really there. In fact a better recording on a good system can give the sense that the music was recorded in a stone church, or in a large hall. That is the goal of stereophonic recording - an illusion of presence, naturalness and reality. How effective that illusion is depends entirely upon those boxes and what's inside them, as well as on the wires that connects them and the space they're setup in (much the same as the space the orchestra plays in has a profound effect on how they sound). I think most folks don't take the time to setup their system to take advantage of that illusion, either because they don't care about it, or are not aware it is possible. What makes one box better than another is whatever the 'one' does to make the sound coming out of the speakers sound more like live music. To refine the performance of any of the boxes means to design the circuitry better, use better components, and make the components you do use synchronize well together. Much like designing a performance race car, or a fine musical instrument. You cannot just randomly throw together the best parts available for the task. To succeed it requires great skill and knowledge, and even some creativity combined with that awareness of how those parts interact with each other to create "the whole". To really appreciate this, as far as the stereo is concerned, you'd have to actually sit down in the right spot (the sweet spot), and listen yourself. Nothing could explain it better, or not explain it at all should you not hear or appreciate the illusion. Just as one may not hear or appreciate the differences in two violins, the same holds true for a stereo; you may not hear, and or care about any differences that exist. Anyway, if you have time when you're next over I'd be happy to demonstrate it to you if you are interested. It is not something you'd appreciate very much at a distance from outside of the sweet spot, though certainly there are many qualities that extend to listening elsewhere which make the music occur as more natural and present. None can match the qualities you'd hear sitting in the right spot.
Please feel free to keep your own comments coming. I've enjoyed the input.

