Thursday, January 22nd, 2009 | by matthew mcglynn
The crew from the Discovery Channel’s “How It’s Made” show got a tour of the Sennheiser/Neumann factory in Wennebostel, and put together a 5-minute broadcast featuring the manufacture of a Neumann U87Ai microphone.
I was especially intrigued to see this, because I toured the same factory last April, and like the Discovery team, was able to watch a U87 being made, from the lathes cutting body parts to the clean room staff assembling capsules, to the final assembly, sweep testing, and packaging. Read more about my Sennheiser/Neumann Factory Tour.
Here’s the How It’s Made video… and below that, the transcript.
Transcript of Neumann Microphone segment from How It’s Made:
People have been doing mic checks since 1876, when the microphone was invented as part of the telephone. Microphones convert sound to a signal that can be transmitted through televisions, radios, and many other things. If you have something to say, you’ll need a microphone to broadcast it.
From the glory days of radio, to stage and screen and the digital age, the microphone has been at the center of it all.
To make a broadcast-quality microphone, they start with a support piece for it. Automated tools carve a brass cylinder to the desired dimensions. They also make a retainer ring for the microphone grille that will anchor the microphone’s metal mesh. They layer three sheets of mesh and align them; then they solder the three sheets together. A punch press forms the soldered sheets into a concave shape. They lower a blade to slice the shaped mesh in half. The two pieces will be used to make one microphone grille.
An assembler squeezes solder paste into a groove in the brass ring. Then he presses the grille halves, which have been joined by a bracket, into the solder-coated ring. On a carousel, a torch heats the rings, and the solder paste melts to bond the grilles to the rings.
A drill punctures a brass disk up to 90 times, to make ventilation holes. Another tool levels the surface and shaves off unwanted bits. This disk will be the backplate for one of the microphone’s capsules.
An assembler brushes away any remaining shavings and fixes the backplate in a holding device.
This plastic membrane has been coated with real gold to conduct electricity. She places the membrane and a plastic ring on the backplate, and then attaches an electrical lead.
She screws the plastic ring down to secure the assembly, and then trims away the excess plastic membrane. This microphone capsule is now complete.
Next, she’ll join two capsules to create the unit that is the heart of the microphone. It converts sound into an electrical signal. An aluminum spacer goes between the two capsules, which face back to back.
Two capsules instead of one means this microphone can be switched to pick up audio from various directions.
A plastic bracket reinforces the assembly. A technician then wires the brass support piece that we saw being made earlier to the electronics system, and then he secures it with screws.
After installing switches, he inserts the microphone capsules in the grille. He screws the capsule assembly to the grille, and joins it to the electronics. He slides the metal casing over the electronics and secures the microphone with a big screw cap.
He checks the switch that changes the directionality of the mic. And now it’s ready for a soundcheck.
The mic goes into a special anechoic chamber. A computer measures its response to various audio frequencies and directions.
Once a microphone has passed this test and some other checks, it’s time to pack it up with great care. Because this mic is delicate and worth several thousand dollars.
Treated properly, this microphone should last several decades. In show biz, that’s longevity.