When we mix a song, there are basically two ways to hear what we are doing as we tweak our faders and spin our knobs: monitor speakers, or headphones. Although each has its advantages and disadvantages, there is general agreement that your mixes will come out better if your listening is done through a pair of high-quality monitor speakers in a sonically appropriate room.
Monitor speakers are designed to give a fair, “colorless” reproduction of your mixes. Over time, and with the use of techniques like listening to CDs you know well through your monitor speakers for reference and EQing the signal the speakers receive from the recorder or DAW to match your room, you will develop a sense of exactly how your mix needs to sound in the mixing studio in order to sound great in a car or a living room, or through an iPod with earbuds.
Having said this, there are reasons to mix using headphones, such as not being able to afford proper monitor speakers or needing to mix late at night when others are asleep. And naturally, you will check each candidate mix by playing it in your car and living room (and through your iPod) to see what final tweaks may be needed anyway. The final evaluation is made through “real world” sound systems, not studio monitors or studio headphones.
These days, with the popularity of portable mp3 players soaring, an awful lot of listening goes on in headphones (or lo-fi earbuds). Given this, you can make the case that it could be more appropriate to use headphones if you are mixing a song that you know will be heard mostly in headphones.-->