M7 capsule in G7?

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Nat

Well-known member
Joined
Jun 3, 2004
Messages
75
Location
Berkshire, UK
Heya,

Could an M7 be dropped straight in to the G7? I ask because in building the G7 with a Soundking 34mm edge terminated capsule, the diaphragm was sucked onto the backplate when I turned the mic on, which I've read means that the polarisation voltage is too high for the capsule. With a centre terminated Soundking the problem went away, but I wondered if anyone here would know for sure an M7 would be alright?

Not that I have an M7 yet or anything, but I'm thinking about trying to buy one soon... will probably be a bit of an upgrade from a stock china capsule! :twisted:
 
Hi Nat,
Don't feel you have to stick with 80V - The circuit is simple enough to change the polarisation voltages without much trouble. Lower voltages can sound good for some capsules.
Stewart
 
Yes - if you get membrane-sucking, then lower the polarisation voltage somewhat untill it behaves right.

I have used the G7 with a M7 at 80V polarisation without problems. But specs may vary.

Jakob E.
 
[quote author="gyraf"]Actually, IMHO the best capsule so far is the AKG original CK12..[/quote]

Jakob, by original do you mean Teflon or brass one?
 
does akg(or whoever repairs their caps now) even reskin with brass if its an original cap or do they go back with teflon?

i cant say i've ever seen an original brass cap going up for sale.

do you remember where you saw the last one, and how much it went for? i see a good amount of m7's going for about 300-600, so i'm guessing an original ck12 is way more than that.
 
Last I heard a real GOOD brass ck12 was over $1000.00 USA this is what I was told by someone I have not checked up on it.

There is no best capsule but there are two very good capsules designs. The brass CK12 and the KK87/67. Most other good capsules are based off them. I have not heard a C37 sony that looks like a different design capsule.
 
I think the C37 capsule is the same as in the C38. My sony C38 seems to be a VERY nice all-round microphone. The capsule does appear different to any others I've seen.

Some pics at my website...

http://www.omnipressor.com/Other/mics.html
 
[quote author="Gus"]

There is no best capsule but there are two very good capsules designs. The brass CK12 and the KK87/67. Most other good capsules are based off them. I have not heard a C37 sony that looks like a different design capsule.[/quote]

Although K67 and K87 are very similar, earlier K67 had some minor differences in construction, which nevertheless, are big enough for me to believe that it sounds better.
Gus, also don't forget M7/K47 design, which sounds different, but also good. I've not heard C37, either.
 
Yes Marik I did forget the M7, K47.

I have read and have been told that The AKG and Neumanns capsules have had changes over the years. One of the many things to learn about microphones.
 
[quote author="Gus"]Yes Marik I did forget the M7, K47.

I have read and have been told that The AKG and Neumanns capsules have had changes over the years. One of the many things to learn about microphones.[/quote]

From my experience, unfortunately these changes were not always for better.
 
and a m49 has an aluminum skinned k67 cap correct?

when a brass or aluminum cap goes in for repair do they reskin it to date of purchase specs and materials or what? why are they going teflon when there is so much more demand for the sound of the original brass type?
is the process of applying different metals drastically different?

thanks.

Taylor
 
Neumanns web site has a nice chart in the infopool section with the different capsules and skins

m49s used PVC on the M7.

The KM53 capsule and early M50 capsules had Al skins IIRC.

Neumann and AKG do not reskin they sell you a new capsule.
 
The Neumann aluminum (and nickel) skins are not deposited on plastic - they are entirely metal. The M49 and M50 were developed before mylar, so to get the tension high enough for an omni mic, metal needed to be used, the PVC they were using on the M7 would break. Even the thick mylar (6-9 micron) would need to be tensioned quite high, and it would likely have also broke. These days, small diaphragm omni mics typically use thin mylar (3 micron) which allows the manufacturer to tune the diaphragm high enough with less tension.

The K67 will not work as Neumann manufactured it with an aluminum skin. The diaphragm would short out to the backplate. All of the capsules using aluminum diaphragms are edge-terminated (so the backplate is insulated from the clamp ring). Also, remember that an aluminum skin is going to be closer to 1 micron thick or so.

Remember that the omni diaphragm is tuned to a frequency at the top end of the audio band, a cardioid or multipattern mic is tuned to a crossover frequency, in fact, not that much different than a crossover frequency in a speaker. From what I can glean from various patents, the original M7 and the original CK12 were tuned with diaphragm resonance frequencies of 800 Hz, but with diaphragm thicknesses and compliances that are a bit different than the current mylar that we use. Current manufacturing practice appears to tune a bit higher - maybe 1200 Hz.

If you want a brass capsule reskinned, you'll need to either send it to someone who does it all the time (do a search and you'll find people that do it), or you can try to do it yourself. The AKG brass capsules should be fairly easy to reskin - you can use coated mylar from a capacitor, but tuning the diaphragm is pretty critical on those mics. I guess, if you're going to do it, it's because the capsule is toast and you don't have anything to lose trying it yourself.
 

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