M7 capsule-article by AG

[JamesM]

Just found this interesting article by Andreas Grosser on the history of the M7 capsule

"M7 capsule-article by AG

M7 capsule

The M7 capsule first showed up in 1933 and was skinned with a 10µm PVC. The material back then had to be – and still is today at MTG as well as STM – casted on water. ( The thickness of the material fluctuates between 10 and 12µm. After the war Neumann Berlin obtained their M7 capsules from Gefell, later on only the membranes . In 1955 Neumann Berlin hired a chemist responsible for the production of membrane films . In 1956 the first M7 capsules with PET polyestermembrane showed up. Those new capsules had a much better longterm stability as well as (because of the thinner membrane of about now only 6µm) the remarkable side effect of better low frequency response. In more than 50 % of all M49 microphones that were fitted with a M7, you can still find the M7 PET capsule, not only (like often times falsely assumed) the M7 PVC capsule. Since 1958/59 the M7 was abandoned and replaced by the K47 capsule. The failure rate in the production process of the M7 capsule was simply too high since you only had about 10 minutes to correctly position and finetune the membrane until the glue started to stiffen . The cogset of the K47 made it easier to finetune the membrane (it now got screwed on instread of glued Because of that the failure rate of the capsules got reduced drastically and so about 80 or even 90 % of the capsules could now be used after production. Back then the PET 6µm membrane film was obtained by the companies that also produced the capacitors."

Interesting!

http://www.andreas-grosser.com/2009/10/ ... cle-by-ag/

[rick]

For what its worth
If andreas says it
I believe it
Lots of information here is unseen elsewhere

[Chris H]

Ah the old Neuman / Gefell collaboration syndrome!

[JamesM]

Yeah and what about the m7 pet polyester? Never new that existed before.