I just came across this, but have heard it’s been around a while, so maybe you folks know about it …
http://www.goldenears.philips.com/en/index.html
For those who haven’t heard of it … it’s fun, frustrating, time-consuming, and educational (IMO)! 
I am at 89%, and believe I will never ever get past that … hearing which of 9 frequencies ranges were cut or boost between two tracks is a skill that I don’t believe is destined to be mine 
. Still, I did learn a lot about how to listen …