M50 aluminum membranes

[k brown]

K Brown this is the earliest version of the M50 capsule. Neumann produced it from 1948 -52. This is a Neumann MM2 microphone built for anechoic chambers. Only 90 of them were ever built. Mine is no.50

I've never read anywhere that is the same capsule used in the M50 . . .

That would explain the thick diaphragm - a measurement mic.

 

[k brown]

@k brown, which transformer is in the M50?

Same one used in the M49 - BV11.

49 and 50 are identical in every regard except the capsules.

But I don't want to derail Tim's thread any further.

 

[kingkorg]

Well I know that the nickel capsule was 0.8 micron but the aluminum diaphragm that came on my M50 capsule mounted on my MM2 measure a whopping 60microns thick which I cannot understand.

Even though we talk Neumann, i'm not sure they knew exactly what they were doing back then, and how hi-fi this thing is supposed to be, what hi-fi even meant in that period. For some of that old capsules i sometimes feel they were just happy if they worked.

 

[Murdock]

I doubt the MM2 uses the same capsule as the M50... There is an official paper from Neumann with all their mics and corresponding capsules. The MM2 did not have the KK53. Maybe they share some similarities but are not the same.

Edit: Here is the paper.
https://www.yumpu.com/en/document/r...ophones-and-capsules-built-by-neumann-berlin-

 

[k brown]

See attached. That cutaway looks nothing like any of the three M50 versions.

 

[soliloqueen]

if it's a measurement microphone and the diaphragm is that thick, i shudder to think what the specified tension is and what achieving it requires.

 

[k brown]

If the customer is expecting this to ever sound like an M50, they're bound to be disappointed; this mic didn't sound like an M50 when new.

 

[Murdock]

See attached.

That's another clue. They write the membrane of the MM2 capsule is 10mm in diameter. M50 KK53 is 12mm...
Also, the capsule used in the M50 is diffuse field equalized. The MM2 is not as far as I know.

 

[Tim Campbell]

The MM2 I believe was the first measurement microphone or at least Neumann's. The internal structure of this capsule appears to be an M50 and it is omni. The thick diaphram may be because this was used for some industrial application. The MM2 is a large badge U47 amplifier (large transformer and capacitors) coupled to this omni capsule on a long extension. This was followed by the MM3 which used the AC701 tube and then the MM5 which used the KM83 capsule. ( after reading the info posted I see the MM5 had it's own proprietory capsule)

I own the mic so I'm expecting it to sound like an MM2

 

[k brown]

That's another clue. They write the membrane of the MM2 capsule is 10mm in diameter. M50 KK53 is 12mm...
Also, the capsule used in the M50 is diffuse field equalized. The MM2 is not as far as I know.

In the case of the aluminum one, actually 12.5mm.

 

[k brown]

The MM2 I believe was the first measurement microphone or at least Neumann's. The internal structure of this capsule is exactly an M50 and it is omni. The thick diaphram may be because this was used for some industrial application. The MM2 is a large badge U47 amplifier (large transformer and capacitors) coupled to this omni capsule on a long extension. This was followed by the MM3 which used the AC701 tube and then the MM5 which used the KM83 capsule.

I own the mic so I'm expecting it to sound like an MM2

Oh, I though you were repairing it for someone. In any case, it's not an M50 capsule. According to the Neumann paper, the MM5 had an even smaller capsule than the 10mm MM2, so not a KM 53 (12.5mm).

 

[Murdock]

The MM2 I believe was the first measurement microphone or at least Neumann's. The internal structure of this capsule is exactly an M50 and it is omni. The thick diaphram may be because this was used for some industrial application. The MM2 is a large badge U47 amplifier (large transformer and capacitors) coupled to this omni capsule on a long extension. This was followed by the MM3 which used the AC701 tube and then the MM5 which used the KM83 capsule.

I own the mic so I'm expecting it to sound like an MM2

Can you share some internal pictures of the capsule?

 

[Tim Campbell]

Can you share some internal pictures of the capsule?

Now I am beginning to agree with you guys. This is an early predecessor to the M50 I will gladly share some photos next time I disassemble it. That will probably be when I figure out what membrane material to use.

 

[GeorgeToledo]

K Brown this is the earliest version of the M50 capsule. Neumann produced it from 1948 -52. This is a Neumann MM2 microphone built for anechoic chambers. Only 90 of them were ever built. Mine is no.50

I had been pm-ing some references (like the spreadsheet I see came up in the thread) but I will relate this here…

According to Uwe Sattler the MM2 capsule (1949) is not the same as the K53 Aluminum (1954), though it is what directly led to it. I’ll see what else I can find out for you about documented differences and the info you are looking for.

 

[GeorgeToledo]

While I have it handy, in case you want this too:

 

[tomas.borgstrom]

Perhaps you already know the former owner of Pearl Bernt Malmqvist or the people at Milab. I'm pretty shure they have been using aluminium for many years. Bernt is very helpful and can probably guide you in some way.

 

[Tim Campbell]

Perhaps you already know the former owner of Pearl Bernt Malmqvist or the people at Milab. I'm pretty shure they have been using aluminium for many years. Bernt is very helpful and can probably guide you in some way.

Yes. I have visited them before though it has been many years.

 

[bremusound]

I read somewhere that the K53 membrane was made of Duraluminium, an alloy with higher tensile strength than pure aluminium.

 

[k brown]

I read somewhere that the K53 membrane was made of Duraluminium, an alloy with higher tensile strength than pure aluminium.

Don't know if it was used in M50/KM 53, but the material was called Duralumin.
https://en.wikipedia.org/wiki/Duralumin

 

[Recording Engineer]

Don't know if it was used in M50/KM 53, but the material was called Duralumin.
https://en.wikipedia.org/wiki/Duralumin

I’ve suspected it being Duralumin for quite some time. I’ve been interested in finding out the true thickness used for a long time. I’ve read 0.8-microns turned super-duper tight and with a 83pf measurement. Everyone has said that’s impossible; must be 8-microns. It seems no one knows for sure. Someone must know though!