While removing hair from my Sennheiser PX-100 (Mark I) headphones, I dented the diaphragm. Immediately after I thought I could hear some distortion in the sound, especially in the mid-to-high frequencies. Below is a picture of the dent. It's about 2x1 mm in size. Sorry about the hair, I've removed it since with tape. :) I tried to remove the dent with scotch tape, but it seemed nearly impossible with the small space to work in.
After using these for months after I dented them, I'm not so sure how much the sound was affected anymore, and whether or not I would notice a clear improvement in sound quality by getting another pair of PX-100's (Mark II). What are your experiences with dents on diaphragms in terms of sound quality loss? I can't say I hear much of a difference between the two channels, but the highs seem to sound a bit more pronounced (maybe slightly distorted too) on the damaged channel. I'm mainly using these on the computer with a Creative X-Fi sound card, so quite a low-spec environment, and more involved enthusiasts would probably notice a bigger difference. :)