[TealRice]

Im just wondering if buying a used headphone can have a negative affect on the sound

 

[SleeStack1]

Since you used the term 'used', not 'abused', you probably needn't worry.

 

[siptu]

i would expect the speaker's surround to loosen up.
how much is uncertain.
whether the looser surround helps or hurts the surround is also uncertain.
i don't think it is a good idea for headphones to start sounding worse just months after owning them.. then again after a year.. and progressively worsening as time goes on.
 
if you EQ your headphones, maybe you need to re-do the EQ after some age.
 
i dont expect the voice coil to 'settle' to one persons ear, as if it melted or twisted some ceramic.. and if it did, it should be able to adjust to a new ear.
 
but it isn't about pleasing an ear shape as much as it is clarity and transparency from the speaker.
 
my first guess is.. buying used should only make the sound a little bit better, kinda like an overclocked computer.