Schoeps CMT-56

[thecr4ne]

I've got two schoeps CMT-56's I'll be working on. This thread is to document and share the process. Here's a quick rundown:

-Both use P48 phantom power.
-One has a non-standard XLR connector, I suspect it was originally a tuchel connector and was changed.
-The other is labelled CMT-54, which I think means it originally had a cardioid capsule, but now has the multi-pattern capsule
-Internally they appear the same, with the following exceptions:
--One capacitor is different between the two (same value, different style)
--Transformer secondaries appear to be jumpered differently. Possibly for different output impedances.
--A few wired connections to the XLR connections vary slightly as well. One has some connections the other doesn't.

When I get a chance, I'll get photos posted and try to dig into the variations a bit more to see if they're significant. Hope to also do some rudimentary sweeps with REW.

 

[thecr4ne]

I requested the schematic from Schoeps and they were kind enough to provide it. They asked that it not be shared so I'll not post it here, though if anyone needs it, just use the contact page on their website to request it.

Anyway, what's clear at first glance is that my two mics are indeed wired for different output impedences. One is set for 200ohm and the other 50ohm. I'll end up setting them both at 200ohm, which should be straightforward.

I also forgot to mention that one of them is stuck in fig-8 mode as the gaskets inside the capsule have worn out apparently. This is supposedly unfixable, but I may have a line on a workable solution. Will share any successes.

 

[thecr4ne]

Regarding the capsule that is stuck in fig-8 mode regardless of pattern selection, I've recently found some useful info, which I've already discussed in this thread which I'll quote in part here:

I've been hunting for this for a while, as I have a Schoeps CMT-56 which is now limited to fig-8 only. Anyway, After a lot of poking around, I stumbled onto a reference to where the schoeps MK-6 capsule diagram can be found: Fig 5-17 in John Eargle's "The Microphone Book" which I accessed by "borrowing" it here: "The Microphone Book" (archive.org membership required)

Anyway I chopped up and re-organized the relevant imagery here:
View attachment 115643View attachment 115644View attachment 115645

First, Thanks for sharing the pics, I have yet to disassemble mine, and this will prove very helpful when I do.

As for the rubber rings, I asked a few follow up questions of Daniel Andreev of Reso Labs as mentioned here, and he was very helpful...


...with Daniel's permission, I'm happy to share that he provided this 3d model of a mold to replicate the rings with silicone. The mold should be produced with a resin 3D printer to achieve the necessary detail. As for the gasket material, he just mentions silicone, and that off the shelf construction silicone can work, also care should be taken to avoid bubbles in the silicone.

I'm currently awaiting a resin print of the mold from a colleague who has access to a resin printer. Once in hand I'll experiment with creating new gasket rings and share my results.

I've also created a separate thread to chronicle maintenance of my pair of CMT-56's.

@Marik was kind enough to share some pics of an MK-6 capsule he's working on in that thread as well:

I happened to have a Schoeps MK6 mechanical three pattern capsule for repair on my bench. Here are pics.