[KingOfTheWild]

Does anybody have any recommendations for a material that absorbs reflections that also won't mess up the sound quality of my headphones? I have never modded a pair of headphones before and I plan to do it for the first time.

 

[Mad Max]

Open-cell acoustic foam is what you want.  Depending on the brand and where in the headphone that you put it, it can help the sound or it can hurt the sound.  You will have to experiment.

 

[KingOfTheWild]

Thanks a lot . . . and thanks for the fast response.
 
EDIT: I don't know why headphone manufacturers don't include this open cell acoustic foam in their headphones from the start . . . I have never had a high end pair of headphones though so for all I know they could have that in them.

 

[Mad Max]

They resort to wool or other fabric materials of varying density and composition to tune the sound and kill resonances or whatever from what I've seen.  Not even higher-end headphones actually use acoustic foam from what I know.  Making the headphone open-back allows them to be lazier.  =p
 
Mid-fi headphones are the ones that most benefit, generally.