[squelchy451]

Hi. I have a secondhand pair of ATH-AD900 and whenever there is a cello or double bass part, I can hear a certain buzzing. It's not unbearably distracting, but it is certainly audible. My cheaper IEMs don't produce this buzzing noise, which leads me to conclude that it's something to do with the headphones.
 
Is there something I can do to reduce the buzzing noise?
 
Thank you

 

[BrownBear]

That's interesting. Is there possibly a hair or some type of debris touching the driver that's causing it? Is it in both drivers or just one side? That would be my first guess. In fact, that happens to me every so often, and I get all paranoid thinking my headphones are done, until I look in there and see a hair just sitting across the driver.
 
What I would do is try to look in there and see if you see anything. Always be careful when inspecting headphones, too. Be gentle. Maybe some other Head-Fiers will chime in as well with some helpful tips.