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Author Topic: Neumann M7 bayonet capsule  (Read 2474 times)

MrJoshua

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Neumann M7 bayonet capsule
« on: September 12, 2011, 01:32:09 pm »

Recently I ran across an old Neumann M7 capsule for the CMV-563 bayonet-style mic and it stirred up an old memory that there was a TapeOp article saying these were compatible with the BLUE mic bodies. I double-checked and sure enough, they are. So I snagged the M7 and added it to my capsule collection, to be used with my BLUE Bottle Rocket Stage 1 body.

I'm happy with the sound, but last time I used it I was trying it on vocals (I quite like it there, by the way, at least on my voice through a Neve Portico preamp) and I noticed that with the Neumann capsule I was getting a lot of mic self-noise. On a suspicion, I tried applying light pressure to the mount to make sure it was seated firmly, and sure enough when I gave it just a light twist the noise floor dropped to being inaudible. I made it through a couple of more vocal takes without any problems, but I'm wondering if there's anything I can do to help make sure it doesn't come back, because the slightest nudge of the mic body was enough to make the noise recur. I'm planning on using some contact cleaner on the spring and pin in the bayonet connector on the capsule. Any other suggestions?

Thanks!

(Oh, and by the way - the M7 capsule through the BLUE transformerless solid-state body sounds pretty freaking good. I haven't had the chance to do a real shootout between it and my Microtech Gefell MT-71S but I'm pretty sure I'm going to be very happy with both mics for quite a long time, as long as I can keep the self-noise down on the Neumann.)
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Joshua L.
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Decatur, AL

klaus

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Re: Neumann M7 bayonet capsule
« Reply #1 on: September 12, 2011, 01:49:05 pm »

Two suggestions for troubleshooting, with unfortunately only one remedy:

1. You have indeed a contact problem. Most likely, the backplate does not see full polarisation voltage, due to insufficient contact between its brass body and the screws which hold it to the mic mount. Alternatively, if the screw-brass intersection is OK, look further downstream, where the capsule mount's electric contact to the mic amp is made. You mentioned the questionable bayonet connector)

2. All of your contact areas are fine, but your touching of the high-impedance capsule parts causes a sudden jolt which awakens a deteriorated diaphragm's capacitance momentarily into full output, only to sag again after the jolt dissipates.

I am not excluding this possibility, because very few M7 PVC capsules from that era are still fully functioning, and with an excellent noise floor.
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Klaus Heyne
German Masterworks®
www.GermanMasterworks.com

MrJoshua

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Re: Neumann M7 bayonet capsule
« Reply #2 on: September 12, 2011, 01:59:24 pm »

Well I certainly hope it's option 1.  I will attempt to clean the bayonet contacts this evening, and if that doesn't work I will continue troubleshooting.  If it's option 2 I'm basically looking at sending the capsule in to be reworked, correct?  Which would be a shame.
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Joshua L.
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Decatur, AL

klaus

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Re: Neumann M7 bayonet capsule
« Reply #3 on: September 12, 2011, 02:06:14 pm »

If indeed it's option #2, yes, it would be a shame to re-diaphragm an original M7, as the sound of any of the aftermarket diaphragm solutions will shift the mic's timbre.

 Let's hope for the best!
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Klaus Heyne
German Masterworks®
www.GermanMasterworks.com
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