I recently purchased 4 of the CM012 25mm electret capsules and noticed that 3 of them looked like they had bumps in the membrane or debris under it, and the center looked like it was touching the backplate. I've attached a couple of photos before the tweaking but it's hard to capture.
After seeing Audioimprov had disassembled link one and they were a pretty simple design, I opened one up to try to fix the issue. It turned out that the wire mesh has almost no clearance from the membrane, and flexing it outward with my thumb fixed the problem. There was also a couple of tiny specs of debris on the membrane which I carefully loosened with the edge of a tissue and removed with some air puffs. All 4 now look perfect when reassembled.
After seeing Audioimprov had disassembled link one and they were a pretty simple design, I opened one up to try to fix the issue. It turned out that the wire mesh has almost no clearance from the membrane, and flexing it outward with my thumb fixed the problem. There was also a couple of tiny specs of debris on the membrane which I carefully loosened with the edge of a tissue and removed with some air puffs. All 4 now look perfect when reassembled.
