So here is something I notice all the time. There you are mixing your latest song in an untreated room with two big speakers in front of your ears. You're mix is sounding great and you're so amped. You bounce the mix and are off to your car to test it out.  Next thing you know is there is a perplexed look on your face wondering why it sounds so bad. How could  you not have noticed the high-hat is barely audible and the bass has too much low end? 

One better way to gauge how your mix will sound on other systems is to try mixing in mono. What does that mean.? It's pretty simple - make sure everything is panned center. Also avoid putting on reverb right away. A lot of inexperienced mixers start panning right away. Try to hold off and see if you can get that mix to sound great without panning. If you can do that I bet you will be a lot happier with your mix when you do start panning.

Mixing in mono was the standard until the late 60's and for good reason. Do you realize that most of the music you listen to has very little stereo separation. People who listen to music on their laptops, computer speakers or from their TV's have little to no stereo. The music you listen to that pours out from Subway or Starbucks is very much in mono. Here is the bottom line. Make sure your mixes sound good in mono. It may not be the easy fix but it is the better fix.