Neumann km84 capsule guts

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kingkorg

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A friend sent me a mic with busted capsule, it measures +20db boost at 10k. Bought of ebay for a lot of money. Anyway i opened it and share assembly pics, as there arent a lot of them on the internet.

NEVER, EVER TRY TO OPEN WELL FUNCTIONING KM84 CAPSULE, OR REMOVE PIN. TENSION OF ALL PARTS AFFECTS PATTERN, FR, SENSITIVITY... YOU WILL BUST IT!!!

I dont recommend removing capsule from the body either, especially on vintage ones like this one, as the pin sometimes gets undone or broken and ruins backplate chamber spacing. It is the only thing holding backplates together.

This capsule is in fact so sensitive that i would never, ever buy used one. Front of the capsule is basically unprotected. Very thin mesh. And it is so sensitive to tensioning of different screws that it's crazy.

Diaphragm tension on this one seems to be 1600hz.

Kauss Heyne says on his forum that sound of these used vary from crazy bright ones to very dark. They should be flat.
 

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RuudNL

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I managed to repair a couple of KM84 capsules in the past.
Often the backplate pins are broken, with the broken part still in the backplate...
The capacity of the capsule is determined by the pressure of the screwring holding the capsule together.
It is important to adjust this for the right value.
The repaired capsules all performed fine, after reassembling them.
 

kingkorg

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What was the value you were going for if it isn't secret?

I was measuring FR after every readjustment of  ring and pin. I got it to be pretty flat.
 

RuudNL

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I measured a couple of KM84 capsules before the 'operation'.
I don't remember the correct value, but it was pretty low, in the order of 36 pF I think.
 

MS Vienna

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I have a K84 in parts in the drawer, so here are some additional pics. Mind the gaps.

One of my KM84 mics is exceptionally well balanced and except from a broad and even presence rise of hardly 2dB ruler flat. Capacitance on this one is 32,5pF.
The other one has slightly stronger low end but also great overall balance. Capacitance is 32,8pF.
Note that these are just values and may or may not correllate with the particular frequency response of these mics.

The KK84s in my KM86 mics have slightly higher capacitance - around 34pF - while these also sound very even.

I strongly recommmend to measure the capacitance also before disassembling such a capsule (ok working one).
 

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MS Vienna

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Here a KM86 without grillecap.  2x KK84 inside.
(I removed the fine mesh in front of the diaphragms since it´s not necessary inside the sturdy grille)
 

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