DT770 Rattle: Normal?

[g500tec]

I have a pair of DT770's (Pro 80) and they sound great. However, sometimes a very faint rattling sound accompanies the lowest frequencies. It seems as if, when the headphones emit really low sounds, the fabric covering the driver vibrates slightly between the driver and my ear, causing a bit of a rattle. It's hardly noticeable, but I am wondering if this normal for 770's? If not, any tips on how to fix it?

 

[krisis1]

http://www.head-fi.org/forums/f4/wie...770pro-281547/

 

[g500tec]

Thanks for the link. Do you think that the fact that I am not using an amp could be part of the problem?