Microphone repair technicians

sonicmook56 · Oct 8, 2008

I'm looking for a good microphone technician to go threw a pair of M49's.

One mic's capsule is 1/2 dead and stuck in cardioid (not good for an orchestra) and the other looses about 1/2 it's output when inverted. (Think it might be a capsule thing also, three tech's have looked at it and can't figure it out)

The big local mic guy in LA has another one of our mic's but has not returned phone calls in 3 month's. Hope he is OK.

Maybe I can just buy two new capsules and replace myself?

SSLtech · Oct 8, 2008

[quote author="sonicmook56"]I'm looking for a good microphone technician to go threw a pair of M49's.

One mic's capsule is 1/2 dead and stuck in cardioid (not good for an orchestra) and the other looses about 1/2 it's output when inverted. (Think it might be a capsule thing also, three tech's have looked at it and can't figure it out)[/quote]

I'm slightly puzzled...

You say that one is stuck in cardioid... so far as I know, the M49 was only EVER available in cardioid, so I'm baffled. -The M50 was the omni version, but NEITHER were switchable or adjustable in terms of polar pattern.

Swap the capules (carefully!!!) and see which (if either) or if both problem/s follow the capsule or the electronics. -Then take it from there.

Keith

pucho812 · Oct 8, 2008

Maybe he means the M149 :? which had 9 polar patterns IIRC

sonicmook56 · Oct 8, 2008

Hmmm... the supply's say they do. I thought if a capsule has two sides you could change pattern by biasing one side differently?

Maybe there not M49's? Only place it says "M49" it is on the PSU with labeling tape.

sonicmook56 · Oct 8, 2008

No, that's not true. I'm pretty sure it's engraved/stamped into the bottom. There all packed up now, don't want to un-pack to look at the moment. :?

gyraf · Oct 9, 2008

M49 has a regelspannung/control-voltage input that goes to the front membrane on the M7, backplates sits on +60, and back membrane hangs off ground.

So yes, it has variable pattern.

Stuck-in-cardiod could be a missing control-voltage either in psu, cable, connectors, or within the mic. But could also be caused by heavier problems in the capsule itself.

M50 is a different story, and an entirely different capsule - omni-only.

Jakob E.

mad.ax · Oct 10, 2008

Since you feel like replacing the capsules yourself, I supose that your not afraid of opening the mics and take a few measurements in order to troubleshoot it yourself...

First thing you need is to check for correct polarization voltages. Then check the 1000pF cap (N°22 on the schemo posted by Jakob). If all these are OK, then you'd need your capsule fixed or replaced...

Axel

SSLtech · Oct 10, 2008

Well... you live and learn!

-This shows you how many M49's I've worked on! :wink:

I just looked it up and yessindeedie, the M49 was remote-switchable. -The only ones I've ever used were the M50 which were the same basic bodied mic, but with an omni-only capsule in there, which are often used in a Decca-tree arrangement. -I knew that the M49 was a large-diaphragm version, but I'd always understood (incorrectly, obvously!) that the M49 was FIXED pattern, as was the M50.

Either way, the audio electronics are plainly working, and the only thing which happens with pattern change is a change of the polarisation on the rear capsule. -An open-circuit coupling (capacitor) between the front and rear center terminals could prevent pattern change, though not likely. -Perhaps more likely -if they're the old PVC M7- is a dead back-half of the capsule... though I'm CERTAIN that you didn't want to hear that...

Keith

mad.ax · Oct 10, 2008

Actually, the M49, issued in 1949 or 1952 (depending on the source), is said to be the world's first condenser microphone capable of remote pattern control...

Another source of possible confusion is the new TLM49 which is a fixed cardiod.

Axel

jensenmann · Oct 10, 2008

with techs in US I can´t help but if you need someone in EU I can drop you some name if you´re in need

fazer · Oct 16, 2008

I have an m249 and the polar pattern is changed from the power supply. However Klaus Hyne (might be spelled wrong) had switched mine with an internal switch that is a screw that holds a metal clip in one position for Polar pattern change or the other direction which forces it into a cardiod only, with 6db more output and therefore less noise.

I always liked the mic in this setup best. I record mostly vocals and standup bass with the mic and cardioid is the best pattern for me.

hope this helps.

Michael P.

sonicmook56 · Oct 20, 2008

Got it taken care of.

On the mic with the inverting problem, the internal shock mount is so old and dry rotted the capsule would touch the metal chassis and cause the drop in level.. The reason why I could never re-create the problem with the mic on the bench disassembled. :?

The mic stuck in cardoid was missing a grid leak resistor. :shock:

All is good now except for the dry rotted internal shock mounts.

nofrets · Nov 27, 2008

Hi sonicmook56,

By "dry-rotted shock mounts, are you referring to the foam ring that sits in a channel just under the grill in the upper shell? One of my M49's, in pieces when I got it, had such a missing piece. Sennheiser USA (and home of Neumann in the USA) suggested that since an original equipment replacement part (not rotted) is unlikely to be found, I should go to the local hardware store and get a roll of appropriate-size closed-cell, adhesive-backed foam weatherstripping. With some careful trimming, I was able to get this to work beautifully. The devil's advocate in me worried about whether the foam might outgas some substance that would harm the capsule, but Sennheiser Tech Support has always led me down the right path so far.

I once also had an M50, whose shock absorbing foam ring was old, rotting, and warped enough to prevent me from removing the grill shell at the 11th hour (morning session booked) when a broken lucite sphere in the capsule assembly had to be replaced. Late night sweating...but finally resolved just in time.

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