On 12/29/2020 11:35 AM, Scott Dorsey wrote:
Paul Dorman wrote:
If Neumann is so secretive, then why did they agree to do a
"How It's Made" video on the U87? This video is WAY too clean to be
from the 60's!
https://www.youtube.com/watch?v=RTZy-ThRXeY
Because that video doesn't show anything important.
And I don't see anything too special here, really. Assuming
they use torque wrenches for the ring that mounts the plastic
membrane, it looks like any assembler could do it.
There are two things they will not show you:
1. How the backplate is made optically flat and parallel to the diaphragm.
The flatness of the backplate will depend on the lathe that it is
cut with.
2. How the diaphragm is tensioned.
They DID show the diaphram tensioned!
The trampoline method that all the Chinese factories are using is the method
that Neumann used back in the fifties, and it can be done well with very
skilled people. A torque wrench tells you something but it doesn't tell you
flatness, it only tells you tension at a few points. If you combine this
with interferometry you can make a capsule with a pretty good null. It's
not easy or cheap and you'll go through a lot of material.
The method Neumann is currently using is automated and results in a ring
with the diaphragm evenly tensioned across it and fixed into place. You
can tour the Neumann plant but they won't let you look into the room where
that takes place.
--scott
Capsule construction is not rocket science.