Many years ago, I was engaged in the repair of audio equipment in our area, serving some world-famous brands. I received many orders for the repair of vintage Neumann. At that time, several Neumann U47 capsules and VF14 were damaged. I contacted Mr. Andreas Grosser in Germany through Neumann. Mr. Andreas Grosser was very patient and had very good skills. He helped me solve all the problems. From that time on, all my damaged vintage Neumann capsules and VF14s would be repaired by Andreas Grosser. During this period, we often communicated and I learned a lot. I also bought some microphone repair tools he made himself, as well as some instruments and accessories that he didn’t need, including several vintage microphones. Because of the special reasons such as the Internet blockade in my area, I couldn’t get these in other places.
He was always very humble to share his knowledge and told me things I didn't know. When it comes to Neumann's capsule technology, it is not rocket science and it is not difficult to repair. However, if you want to make a capsule with the same performance as Neumann, it is very challenging. Not only do you need some specially customized machines, but you also need rich experience and technology. Because Neumann has not leaked their capsule technology to the outside world, their process is judged by experience. When talking about Neumann's drilling technology, he said that Neumann's 34mm drilling process is carried out in several times. The internal structure is relatively special and requires a special drill bit, and then stamping may be required. After he passed away, I also repaired many old Neumann capsules myself. I personally verified his views that the manufacturing process of Neumann's old capsules is not as simple as it seems on the surface.Modern processing technology should be able to achieve this, but the cost will certainly be very high. It also requires the manufacture of some special fixtures and drills. However, it may be impossible to accurately test the impact of these special drilling structures on the sound. But why did Neumann insist on doing that? Not only did it increase the cost, but it also increased the difficulty of manufacturing. So in the end we can conclude that there must be a reason for doing this.
Glad someone is finally doing this now.