Hi, I'm with Wayne sort of. I use a computer with calibrated mic and octave analyzer. Feeding in pink noise (the program can cancel out existing ambient noise) and looking at the display. That gets the overall balance right and eliminates large nulls and peaks. Then critically listening to music I and familiar with. Usually several types. Some vocals, some just instruments and several different genres. This part can tell if the presentation spatially is good. The PC can't tell you too much about that and while the display might be flat from a power perspective it might be way off on reflections.
This sounds quite complicated but I suppose this is one of those things that we all need to learn somehow. A lot of people are only content with any sound that emanates from an audio equipment. There's a great need to ensure that proper testing is done.