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Stinky M7 on a CMV-563?
Old 19th May 2006
  #1
Lives for gear
 
4 Reviews written
🎧 15 years
Stinky M7 on a CMV-563?

My M7 capsule *stinks*.

Like a pop filter after a few hip-hop sessions (they don't call it 'spitting' a verse for nothing).

Could this affect the sound? How does dried spit on a capsule 'sound'?

It has a really profound proximity effect...could this be the cause?
Old 20th May 2006
  #2
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gainreduction's Avatar
 
🎧 15 years
Quote:
Originally Posted by thejook
My M7 capsule *stinks*.

Like a pop filter after a few hip-hop sessions (they don't call it 'spitting' a verse for nothing).

Could this affect the sound? How does dried spit on a capsule 'sound'?

It has a really profound proximity effect...could this be the cause?
Dried spit and any other contamination on the capsule sounds like cracks, pops, strange background noise and other undesired fx sounds.

Lots of moist/dirt can make the capacitor collapse as particles establish contact between the front and back plate of the cap, thus causing a "leakage" in the cap which you will hear as noise, cracks etc...

If a dirty capsule sounds muddy and undynamic..., I don't know. Maybe someone else can chime in here.

Since you own an original M7 you can get a replacement capsule from Microtech gefell. It's not a trade-down, they make them to the old specs. The Gefell M7's are outstanding capsules. Cost of M7 replacement at Gefell is 480 euro. They take pride in their old mics and give great service. They give an free evaluation with quote of the cost if you send them the mic. 480 euro is worst case scenario.

Other cmv563 tips that I can share since I'm in the process of hot-rodding my own:

- Have a tech replace the resistors and caps to high-quality ones. Make sure every component is up-to-spec. My cmv563 sounded like coming from a different planet after re-capping. Major, major, major difference.

- Replace the original RFT tube (if you have one) with a good NOS Telefunken.

- I learned from Oliver Archut @ Tab-Funkenwerk that the weakest part of these mics is the transformer. Oliver makes a custom replacement x-former that I have ordered and waiting to ship to me. I am very curious about what it does sonically to the mic. Supposed to improve quite a lot. I'll report back.

- Check the PSU aswell to make sure you get healthy and stable current out of it. If it has a pre-amp in it, bypass it.

- Get a good mic mount

An up-to-spec cmv563 with a healthy M7 capsule, good tube and good x-former is a great mic ! Sounds as good as anything else, it's really worth the cost restoring it up-to-spec.
Old 20th May 2006 | Show parent
  #3
Gear Maniac
 
🎧 15 years
My CMV551 + M7 has quite a large proximity effect aswell. Weve modded my M7 so that when i stick a small rare earth magnet to the bottom of the grill, it closes a switch that conects the rear diaphram, making the M7 omni. It looses the prox effect but otherwise sounds the same. Makes it great for close micing vocals or even sticking it right in front of the soundhole on an accoustic guitar.

On restoring the mic:

I think its kinda weird to buy a mic and then replace every part except for the case and capsule. Id say if a mic needs that much work, its not worth getting.

BUT I agree that you should change all electro caps inside the mic (the 0.5uF can be changed to an MKT) and probably the tube. I bought a few EC92s and picked the one with the lowest noise (about 4db less). Also its probably a good idea to replace the cable and clean the tuchel connectors and pins on the mic and PSU.

Maybe mine has a particularly good transformer, or maybe the 551s and 563s have different xformers, but I cant hear any problems in this area. Mine just sounds valvey, warm but clear and bright at the same time. What youd expect from a classic old mic.

I think that if your PSU is working properly your mic will sound good. Of course if youve got one with the internal preamp, bypass it. But unless the mic is humming or the PSU is somehow damaged your mic will sound good. Sure, if you want a new super stiff PSU then great, but where do you draw the line between and old mic and a new one?

My M7 is original and its pretty bright sounding (in a nice way) but definitely not in spec. We had a CMV with a new gefel M7 in the workshop recently and it sounded awesome, but much deeper and a tad smoother than mine. More like a U47, whereas mine almost sounds a bit like a bright C12. Id love to get a new M7 just to have both flavours. I didnt think either one was better outright.


If youre careful, open up your M7 and take some pics of the capsule. We should be able to tell if its too dirty from some pics.



M
Old 20th May 2006 | Show parent
  #4
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gainreduction's Avatar
 
🎧 15 years
I don't think there's anything wrong with restoring an old mic. It's still the same if you change the capsule to a new identical one. The M7's are still made exactly the way they we're meant to be back in the day. I see it as maintenance, changing worn out parts.

Same goes for caps and resistors. Mine is from the late 50's and it would be a miracle if no parts need replacing after 50 years of use.

Changing a tube is no biggie either. Why use a bad tube when you can have a good one ?

Of all the tips I shared, the only mod is the x-former. The problem with the "east German Neumann x-formers" (as with most parts) was the availability of good quality parts and material in post WW2 East Germany, especially after the Berlin wall was built. Georg Neumann personally was very involved in the Neumann-gefell factory but had to stop visiting after the wall was built. Basically all communication was cut down between east and west.

After the wall came up, parts and material was sometimes hard to find but the factory now beeing government-controlled had a monthly quota of mics to build and had to use whatever was available. Rumour has it that even some M7's from this time period aren't even coated with gold...

Back to the x-formers. According to Oliver Archut, who makes the replacement x-former, the x-former was the part suffering the most from the varying supply of proper material to make them from. You might have a good one, you might not. The point is, you don't really know until you've compared to something. That's why I ordered one.

With 50 yr old parts and some of them (maybe) of questionable quality, how do you know you really get the most out of your mic ?

I was recommended not to change the psu as long as it works.

I'll say it again, up-to-spec it sounds quite amazing.
Old 20th May 2006 | Show parent
  #5
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gainreduction's Avatar
 
🎧 15 years
Quote:
Originally Posted by moogus
I think its kinda weird to buy a mic and then replace every part except for the case and capsule. Id say if a mic needs that much work, its not worth getting.
There aren't really a lot of ways to get a mic with a real M7 capsule. Your choices are quite limited if you want a M7. That's why I got mine.
Old 20th May 2006 | Show parent
  #6
Gear Maniac
 
🎧 15 years
Quote:
Originally Posted by gainreduction
Back to the x-formers. According to Oliver Archut, who makes the replacement x-former, the x-former was the part suffering the most from the varying supply of proper material to make them from. You might have a good one, you might not. The point is, you don't really know until you've compared to something. That's why I ordered one.

Id love to hear more about this. Can he tell you what the variance is and if theres any way to see or measure it? Also how does it effect the sound?


M
Old 20th May 2006 | Show parent
  #7
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gainreduction's Avatar
 
🎧 15 years
Quote:
Originally Posted by moogus
Id love to hear more about this. Can he tell you what the variance is and if theres any way to see or measure it? Also how does it effect the sound?


M
This is from an email that Oliver sent me when I asked about the transformer upgrade:

"we made this x-former as an upgrade for the historic Gefells made during the Soviet occupation, in that time it was quite hard for the formally Neumann company to get a hold of real transformer lamination so sometimes they took anything to make their monthly quota.

After the iron curtain came down those mics flooded the market, and even a good capsule the x-former was the limiting part.

When we designed the upgrade only goal was to keep it the same size than the historic U551 but that's all. "

Link to transformer page @ Tab-Funkenwerk:

http://www.tab-funkenwerk.com/id2.html

I hope to get mine soon, I'll report back how it sounds compared to the original.
Old 20th May 2006 | Show parent
  #8
Gear Maniac
 
🎧 15 years
Make some recordings before and after if you can. That would be interesting.

Youve got a 563 right? Not a 551?




M
Old 20th May 2006 | Show parent
  #9
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gainreduction's Avatar
 
🎧 15 years
Yep, 563 here.
Old 20th May 2006
  #10
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4 Reviews written
🎧 15 years
Thanks for all the replies!

I don't know how to (carefully) open an M7 capsule..I suspect it has something to do with the pin at the top, but it's not a screw or anything...

I get the high end goodness out of it when i back off of the mic a bit. It's just when I'm close up that I get that huge bump at like 200 Hz. I don't hear any intermittancy from the mic at all; if there's spit, then it only smells and doesn't seem to be affecting the audio.

The m55 capsule, though, is a lot brighter than my M7. It's supposed to be, from what I understand.

If you can let me know how to open this capsule without damaging it, I'd love to post some pics.
Old 20th May 2006 | Show parent
  #11
Gear Maniac
 
🎧 15 years
Ok here goes;

That thing at the top of the head is actually a screw, just most of them have been filled with putty to hide the screw head. You have to scrape it out so you can get to the screw underneath.

Take that screw out and remove the silver collar that its holding down. This may be stuck and require a little force or levering.

Now notice the little grub screw on the shaft of the capsule near where the head joins it. Its on the opposite side to the neumann logo. Loosen it or take it out completely, but dont loose it. Now you should be able to gently rotate the head and slowly pull it away from the shaft.

When its free, carefully pull the two pieces appart until the spring wire that comes from the bottom of the head is free from the shaft.

There will be a small piece of brass or copper inside the shaft. You might want to take it out so it doesnt fall out and go missing while youve got everything in peices.

Now gently pull the two halves of the head appart. You might need to lever them a little with something plastic (so as not to scratch anything). Do this very carefully so you dont break the wire coming from the capsule to the spring thats now hanging from the head.

If that all went well, your M7 is now photographable (is that a word?).

See the two metal tags below the capsule? One has the wire from the front side of the capsule and the other is conected to the back side. If you join them, you get an omni M7. Try it. Very useful.


Now when you put it back together, MAKE SURE the little copper shim goes back where it was and isnt pushed up as you put the head back on the shaft. Ive done this once or twice and its shorted out the capsule, resulting in no sound.

Its all easier than it sounds, just take it slow and careful the first time.



M
Old 20th May 2006 | Show parent
  #12
Lives for gear
 
4 Reviews written
🎧 15 years
Okay, succeeded in opening the cap...

Is that tarnish normal?!!!
Attached Thumbnails
Stinky M7 on a CMV-563?-p1010026.jpg   Stinky M7 on a CMV-563?-p1010030.jpg   Stinky M7 on a CMV-563?-p1010031.jpg   Stinky M7 on a CMV-563?-p1010033.jpg  
Old 20th May 2006 | Show parent
  #13
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matucha's Avatar
 
1 Review written
🎧 15 years
unfortunately this is not uncommon... what it needs is a doctor

I have one in the good condition and one in condition similar to yours... the corroded one sounds much duller than the good one. But at some uses I prefered the "wrong" one ;-).
Old 21st May 2006 | Show parent
  #14
Gear Addict
 
phelbin's Avatar
 
🎧 15 years
Quote:
Originally Posted by thejook
I get the high end goodness out of it when i back off of the mic a bit. It's just when I'm close up that I get that huge bump at like 200 Hz.
Same with mine. I've found that my M7 sounds best 12-18 inches away, and off axis a bit too. That would definitely help with your spitting issue too.



Quote:
Originally Posted by gainreduction
- Have a tech replace the resistors and caps to high-quality ones. Make sure every component is up-to-spec. My cmv563 sounded like coming from a different planet after re-capping. Major, major, major difference.
I have an M7 with a 563, and both serials are around 11,000, which someone told me means that they were made in the mid to late 60's. Anyway...I've noticed a slight metalic sound to the mic that is more apparent on certian voices. It doesn't bother me a ton, but my partner is convinced we need to get rid of it. Is that the sort of thing caused by the inferior components often used in the late 60's, and would mine benefit from some upgrading?
Old 21st May 2006 | Show parent
  #15
Gear Maniac
 
🎧 15 years
Have you ever opened it up? If not, you definitely need to change the caps and the almost certainly the tube. Also check the capsule to see if its not in similar condition to the one in the pics above.

The metalic sound you describe sounds like the tube is microphonic. Also check you PSU to make sure it doesnt have a transistor preamp in it.



Thejook:

Wow your M7 is quite different from mine. Is yours the long necked or short necked one? Mine is the long one and doesn have that big plastic insulator like yours does.

No that tarnish is bad bad bad, im surprised it even sounds remotely good. I think you need to send it to Gefel asap.



Theres a big thread on The Lab about these mics where I detail the mods Ive done to mine and lots of other people talk about theirs.
http://www.prodigy-pro.com/forum/vie...hlight=cmv+563
Old 21st May 2006 | Show parent
  #16
Lives for gear
 
4 Reviews written
🎧 15 years
Moog-

Mine is the short necked one.
Old 21st May 2006 | Show parent
  #17
Gear Maniac
 
🎧 15 years
Well, if thats what Klaus thinks Id defer to him. I certainly dont know more about capsules then he does!

Its hard to imagine that whatever that dark stuff is, its not effecting the sound though. Id love to know if Klaus knows what it is and why its there.

My M9 (omni) has a similar coating on it and it sounds terrible, but I think the M9s never sounded good in the first place.

If you get the capsule replaced, it will sound more like it did originally. So I guess it depends if you want that or not. Personally Id love to have both, but I know my M7 sounds great, just its definitely not in spec.

Perhaps you could post a short voice recording for us to listen to? I should be able to tell if its in the same ballpark as mine from that.


M
Old 21st May 2006 | Show parent
  #18
Lives for gear
 
4 Reviews written
🎧 15 years
Here's a short recording.

For what it's worth, I compared my CMV to another CMV from a studio I used to work at (by way of a session I still have from 4 years ago, with me singing on it!), and they sound pretty much the same.
Attached Files

CMV Test audio.mp3 (188.4 KB, 1145 views)

Old 22nd May 2006 | Show parent
  #19
Lives for gear
 
4 Reviews written
🎧 15 years
Voice recording on previous post
Old 22nd May 2006 | Show parent
  #20
Gear Maniac
 
🎧 15 years
Im not sure if its a room issue, but that clip sounded kinda harsh to me, in a way that Im pretty sure my CMV wouldnt. Have you replaced the caps and tube? Sounds like a bad tube, perhaps.

Out of interest, what mic pre did you use?


It when you say 'hey hey hey' that I notice it...

Hmmm Im not sure...



M
Old 22nd May 2006 | Show parent
  #21
Lives for gear
 
4 Reviews written
🎧 15 years
Yeah, it's a boomy boomy room.

Chandler Germanium pre.

Haven't replaced anything; pretty sure it's all original since 1967 (which is on the documentation)
Old 22nd May 2006 | Show parent
  #22
Gear Maniac
 
🎧 15 years
I think you should change all the caps and the tube then post another sample. There are only 3 in it from memory. Have you checked to make sure your PSU doesnt have the horrible transistor preamp in it?


It doesnt sound bad theres something weird about the top end, and when you say hey hey hey that makes me think worn tube. Its worth a try anyway.


M
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