Can mic capsules be recoated

[Tim Campbell]

Aluminum is much more brittle than gold. I have seen very cracked pvc diaphrams work perfectly as long as they were not subjected to moisture.

 

[Екатерина]

There are many ways to repair it, such as purchasing a new capsule, using a single sided conductive film instead of the entire film, or using screen printing to make a single sided conductive film

 

[spiders]

Aluminum is much more brittle than gold. I have seen very cracked pvc diaphrams work perfectly as long as they were not subjected to moisture.

I can attest to this one. I have a UM57 with a M7 in it that looks horrendous but sounds wonderful.
It’s been exciting and informative for me to read all of this. I don’t know if I’m being idealistic or precious about things, but if possible I’m trying to preserve the original diaphragm for my capsule. I sought this mic out specifically for the capsule, and as such would love to revive what I have. Fwiw I did not know the condition of the capsule prior to buying it, but probably would have gone ahead with buying it anyways.
So this raises another question for me, all variables being the same (thickness, etc) how does the diaphragm affect the tone of the capsule? Does a new membrane possess more elasticity than a old one. Perhaps less? Does the backplate and internal design do more of the heavy lifting in a capsule?

 

[Tim Campbell]

Well honestly if you really want to preserve the original membrane anyone with an deposition chamber can remove the membrane and put new gold on it. The membrane is glued to a ring and can be taken out and put back in. The membrane however is just a 6 micron piece of PET film that is sputtered on one side so if you don't mind having a new membrane anyone with access to membrane material can replace the membrane. You won't notice a difference in the sound either way. The trick is assembling it without trapping dirt behind the membrane and knowing the proper tuning frequency.

 

[Екатерина]

In fact, the tuning frequency of most center taps is 470HZ, and the edge tap type has a 30mm outer diameter characteristic tuning frequency of 850HZ and a 34mm outer diameter characteristic tuning frequency of 1000HZ. I hope this will be helpful to you

 

[Tim Campbell]

In fact, the tuning frequency of most center taps is 470HZ, and the edge tap type has a 30mm outer diameter characteristic tuning frequency of 850HZ and a 34mm outer diameter characteristic tuning frequency of 1000HZ. I hope this will be helpful to you

I would be very interested how you came up with these measurements. They are not what my own experience has taught me. I have never seen a membrane tuned below 800hz at 60v polarization without collapsing. The Sony C37 is polarized to 70v or higher as I remember.

 

[gyraf]

..perhaps because the center-terminated capsule stiffens up quite a bit / ends up at higher resonance frequency when later center-supported? I reckon measurement done before-center-termination?

/Jakob E.

 

[spiders]

I believe that the polarization voltage on the Sony C3x series mics is quite high indeed. IIRC it’s quoted at 140v in the c37fet, for example

 

[GeorgeToledo]

re:M7

 

[JPO]

I would be very interested how you came up with these measurements. They are not what my own experience has taught me. I have never seen a membrane tuned below 800hz at 60v polarization without collapsing. The Sony C37 is polarized to 70v or higher as I remember.

The C-37 has 130 volts polarization measured at the capsule.

 

[bremusound]

Interesting! May i ask from which document this excerpt is taken? Thanks

View attachment 116457

re:M7

 

[Tim Campbell]

The C-37 has 130 volts polarization measured at the capsule.

Yes I remembered that it was high but has been quite a few years since I have looked at anything but the capsule.

 

[GeorgeToledo]

Interesting! May i ask from which document this excerpt is taken? Thanks

You can find it here:

https://www.worldradiohistory.com/UK/Wireless-World/50s/Wireless-World-1953-02.pdf

 

[k brown]

As a slight aside, assuming proper manufacture in both cases, what is the advantage of gold over aluminum? The Okatava MK012 capsules are aluminum-sputtered and sound very good.

 

[Gus]

I don't think you could deposit gold on a used membrane effectively.
First you would need to clean the organics off the capsule and ring as well as the old gold.
Then pump down the membrane and mounting ring in the vacuum and glow discharge the surfaces to clean them up
Now how well will the PET hold up after the work
PET needs prep to work well in capsules
Then you need a mask for the metal evaporation.

 

[Екатерина]

I would be very interested how you came up with these measurements. They are not what my own experience has taught me. I have never seen a membrane tuned below 800hz at 60v polarization without collapsing. The Sony C37 is polarized to 70v or higher as I remember.

This comes from some special capsules, most of which have a diameter of 34mm, and some have a special size of 30mm capsules. The distance from the diaphragm to the electrode plate is 60 μ M instead of the common 40 μ M 30 μ m. This data comes from some factories

 

[cyrano]

The C-37 has 130 volts polarization measured at the capsule.

B&K has measurement capsules polarised with 100 or even 200V. Some switchable in the preamp. Funny, but DPA mics mostly are electret. The opposite side of the spectrum?