Thank you for the reply.....I gonna get the ath m50 then=D...
Frequency response
Frequency-response specifications in full-size loudspeakers are generally pretty useless in predicting sound quality, but headphone frequency-response numbers are even worse. Manufacturers have routinely exaggerated frequency-response figures to the point that they're irrelevant. Even the flimsiest, cheap headphones routinely boast extremely low bass-response performance--15Hz or 20Hz--but almost always sound lightweight and bright. Generally, bass buffs will be happier sticking with larger 'phones.
Impedance
Generally speaking, the lower the headphones' electrical impedance (aka resistance), the easier it is to get higher volume. But here again, the low impedance is no guarantee of high volume capability; other factors can still limit loudness potential. Since many MP3 players have feeble power output--the iPod is a notable exception--smart shoppers should check the loudness before purchasing any pair of headphones. To be sure, listen with your player.
Source from cnet...