It is like asking "How do you know if/when you are enlightened?" For a Buddhist follower, it is a difficult question to answer other than saying, "You know when you know."
Jokes a side, let me try to answer from my point of view. I know my setup is performing at its very best when it reproduces human voice male/female just like they are in my listening room. For my tastes, stereo sounds great when Ella, Lady Day, Louis Armstrong, Jim Reeves, Lata Mangeshkar, Nana Mouskouri, Luciano Pavarotti, Dame Kiri te Kanawa, and many other artists sounds alive in my room. Of course, there are other measures as well. But recognizing and relating to the voice of your favorite artist should be something most everyone can do.
This should not require any special training or skill such as hitting the race track and getting used to driving a Porsche! Some actually require such training as they do driving a Porsche. They are bit handicapped with driving disabilities. But most folks should be able to recognize and enjoy the voices of their favorite artist from their stereo set up. Hope this helps.