It is said that that usually quality headphones does not sound at its maximum potential right out of the box.By playing it for long hours the sound quality will gradually "open up".Can't give you the technical explanation but thats the theory

After exhaustive research about a good pair of headphone (under RM 500), i decide to buy grado SR80. It really worth every single cent. Really worth. Compare to my zalman 5.1 and Koss or Altec headphone, grado stand out from the crowd obviously. The bass is more than enough (i am techno mp3 lover fyi) and the treble is i max my x-fi trebble setting could pierce my ear drum. Thats my recommendation about good grado headphone.

For the burn in process, any song or sound could do. Even though, you are not force to do so. You may enjoy your good pair of headphone eventually sound better and better. Yes i notice the different ... I just play mp3 and listen to it.

How the burn in process improve the sound. Well, if you buy a good set of speaker, it require some burn in too. It related to the phisical and material of diafragm. Fresh from the factory, the diafragm kinda not so elastic. The output of the diafragm sound less transparent and lack of bass (for my grado). Time to time, when the burn in process enough i think, i never imagine that the bass could be very good...more to thumping now.

well u let it also keep on running for 24 hours...
i highly doubt yur player or yur headset will masuk icu.....

Means drive. If a 32ohm earphone compare to a 250ohm earphone, 32ohm is easier to drive even using a portable device like ipod, no amp are required. For 250ohm, an amp is needed to drive because of the high impendance, without an amp, it will be nt loud enough.