[lilandrew21]

While recabling my new dt880s, I managed to ruin one of the cloth pieces that goes into the back of the driver housing while using a heat gun on some heat shrink tubing.  Although the headphones still sound good without this cloth in the back I am wondering if anyone knows whether it is a cosmetic or functional part of the driver.  I assume that it is so one can see into the driver from the outside and is more of a cosmetic item, but I feel as if the sound has slightly changed but I am not sure if it is due to a recable or the fact that the cloth is no longer in the drivers (possibly more treble and sibilance).
 
If it is a functional piece of the driver... can anyone think of something I can replace it with... like a coffee filter? seems to have the same consistency and perforation. Would Beyerdynamic possibly send me a new piece?  it surely cannot be an expensive part as its basically paper.  Thanks in advanced. 
 
 
I recycled this picture from the dt-880 closed-back thread rather than taking my own picture of my ruined cloth.