[Voidrunner]

Bit of a necro post, but I just did basically this same mod to my DT 990 Pro's. I cut out a circle of felt and placed it in the spot shown above. Seems to have drastically reduced the somewhat overly sibilant quality of the DT 990 Pro. Made it much less fatiguing to listen to at volume. Seems to have left the remainder of the spectrum largely untouched. Well worth it, in my estimation. 

 

[MorrisL]

  Bit of a necro post, but I just did basically this same mod to my DT 990 Pro's. I cut out a circle of felt and placed it in the spot shown above. Seems to have drastically reduced the somewhat overly sibilant quality of the DT 990 Pro. Made it much less fatiguing to listen to at volume. Seems to have left the remainder of the spectrum largely untouched. Well worth it, in my estimation. 

What kind of felt did you use to achieve such a result? I love the 990 bass but hate its treble with a passion. I'd love to be able to do what you have done. It will basically be a better 880, with wider sound stage and fuller bass.

 

[Voidrunner]

Just regular felt, like you would buy at a fabric or crafts/hobby store. 

 

[Maverick255]

Can you reupload pictures?