Sort of related to headphones:
There's been a lot of talk on mixing and mastering with headphones, but there's one big thing that people overlook when doing so.
Headphones force the sound into your ears (not a very technical term, I know), which is great if you're producing music to be listened to...on headphones.
If you're making music to play live, play on good computer speakers, good car systems, etc, then mixing and mastering with headphones is going to present a ton of problems. The most notable of which is:
Direction
Now I'm not talking about panning here. Obviously somebody can easily mix sounds into the left and right channels of headphones and speakers alike.
What I'm talking about is your ear's natural ability to create a sense of depth and direction to the sounds it hears, by your brain determining the direction of various sounds and the time difference that it reaches your left/right ear.
Simply put, when you mix and master on headphones, and then play your song on a big PA system, it may sound like crap. Why does it sound like crap? Well, you've created a mix that fits perfectly when right/left stereo information is being directly fed directly into your right/left ear, however there is no determining factor whether or not you've created a mix that allows a person to decipher that naturally, when listening without headphones, because you have one giant difference between headphones and monitors.
With monitors your right ear hears music from the left channel, and vice versa, which is called bleed through. With headphones, only your left ear hears left channel, and only your right ear hears right channel.
Reference:
http://audio.tutsplus.com/tutorials/mix ... eadphones/