The violin is simple; first of all I'm looking for long sustained notes to judge the timbre of my speakers. In regard to quality; I've been listening to violin since I can remember, on the radio, the movies, and I'm qualified to judge by comparison. As an example;
https://www.youtube.com/watch?v=tt2NIDtp-Ls
This sounds like 'crap' on the computer, must be good violin; here I can compare violin and cello. I'm much more interested in the sound of the violin and the cello than what they're playing.
Here are more good sounding violins;
https://www.youtube.com/watch?v=5iimxAJPPLY
When my speakers reproduce the sound of these instruments perfectly, I know all is well in the midrange; I'm not listening for pleasure, but the quality of the timbre; especially on any long sustained parts of the program.
Oscar Pettiford "Stardust" is so well played using nothing but bass;
https://www.youtube.com/watch?v=Ut6LinT-DJI
More coming tommorow.........