That's a silly notion. You mix to sound good on all devices, not just one (headphones). A high quality and experienced mix engineer will spend sometimes years d

That's a silly notion. You mix to sound good on all devices, not just one (headphones). A high quality and experienced mix engineer will spend sometimes years developing his/her ears and learning the room acoustics and learning their monitors' responses. This allows them to use 1-3 pairs of monitors in their studio that they know will "translate" (which means "that will sound good on any device"). Room acoustics and monitoring are a science, not an art, so this is easy stuff that anyone can do regardless of budget. Guys on a budget, however, will get one pair of monitors/headphones, do their mix, and go listen to that mix in lots of environments - cars, home stereos, beat boxes, etc. They'll hear how it sounds outside of the studio then they'll come back and make adjustments. This is how you "learn your monitors" - you are trying to learn about "500hz sounds too low in the studio but, if I bump up 500hz in the EQ, it sounds fine in the studio but then it gets muddy anywhere else". This is just how you do it.