Hello @jisoo kim,
Thank you for your post. We get this question often from customers asking how to replace the black felt or black circle inside the ear canal. This black circle serves only one purpose: it is intended to keep dust, dirt and debris from getting inside the tiny holes of the microphone capsule.
Inside each ear canal of a 3Dio microphone is a microphone capsule. The capsules used for the 3Dio FS and 3Dio FS XLR models are 10mm in diameter and include a very thin black felt cover over the capsule shell. This thin felt cover is applied to the capsule shell using a spray adhesive prior to being installed over the capsule's diaphragm, which is permanantely adhered to the backing board.
When this felt cover is rubbed off or removed, there is no way for us to reapply the cover to the capsule cover without risking getting adhesive inside the capsule itself or getting adhesive onto the diaphragm.
Alternatively, we can replace the entire capsule itself. Because all of our microphones are identically matched left and right, if we replace one capsules, we must replace the other with an exact match. Replacing the capsules requires that we remove both ears and the process is somewhat laborious. As of late 2022, the cost to replace both the capsules in our FS and FS XLR models is $80 + shipping.
If you wish to have the capsules replaced, please email us at firstname.lastname@example.org and we can arrange the replacement.
I hope this information helps. Let me know if you have any other questions.
3Dio Customer Care