Something you might not know about condenser microphone capsules

[c7sus]

First I've heard that gold can oxidize or tarnish. What can make that happen? Is it even possible in a normal environment? What were they doing with that microphone anyway?

This thread seems to have been an engineer (or wanna be engineer) making a pitch for a new design. Hey, I'm all for trying new materials and new approaches. It seems though that the arguments were being presented in a rather underhanded manner. How about titanium coating (which is lighter than gold, but heavier than aluminum) and filling the capsule with helium to change the speed of sound to compensate for it? Alternatively we could coat the thing in snake oil which does not tarnish unless you look at it.

browneyes, if you are pitching a new design or product - get to the pitch. Don't try to disguise it as education.

The gold doesn't oxidize. But the impurities in the gold alloy do.

 

[c7sus]

Yes, this is the solution - I can sell you some for the very low price of £10,000 per fluid ounce.

Same price as the oil for electrostatic delays.

 

[dgatwood]

The gold doesn't oxidize. But the impurities in the gold alloy do.

Gold actually does oxidize (Au2O3, for example). It just doesn't oxidize significantly in air or (clean) water at room temperature. Toss the gold into aqua regia and tell me again that it doesn't oxidize.

 

[c7sus]

See "normal environment" above.

 

[moresound]

The gold doesn't oxidize. But the impurities in the gold alloy do.

So we aren't talking 24K here, what is the normal K of the gold found in microphones?

 

[POUNTBOY]

hello harvey!

We have not heard the voice from Harvey, how are you?

 

[higain56]

Most helpful info in this thread to me is the comment about the "breath test". I had not heard about that. I take pretty good care of my mics but I do sometimes leave them out. My C AKG 414 B-ULS still works great but it is also about 30 years old and I wonder if it needs some TLC.

There is no degradation that I can tell, so I should just let my ears guide me here.

Rick

 

[Chili]

Great to visit this thread again.

So we aren't talking 24K here, what is the normal K of the gold found in microphones?

If the gold is sputtered onto the foil, then I'm pretty sure it's pure gold. I always thought the gold layer was around 5000 angstroms thick. I forget where I read that tidbit. The mic manufacturer might use a "glue" layer between the gold and the pvc foil, but it isn't an alloy. The glue layer is probably titanium, platinum, aluminum or some mix of the three. Or maybe the gold sticks to the foil by itself.

 

[moresound]

Am just surprised that the Rothschild family allows their gold to be used on microphones in the first place.

 

[John Willett]

Great to visit this thread again.



If the gold is sputtered onto the foil, then I'm pretty sure it's pure gold. I always thought the gold layer was around 5000 angstroms thick. I forget where I read that tidbit. The mic manufacturer might use a "glue" layer between the gold and the pvc foil, but it isn't an alloy. The glue layer is probably titanium, platinum, aluminum or some mix of the three. Or maybe the gold sticks to the foil by itself.

Gold isn't the only material used.

Some use aluminium instead of gold (Calrec used to do that) and some manufactures use metal diaphragms made from Nickel or Titanium (eg: Gefell, Neumann and others).

 

[ecc83]

In all this, sometime accurate, sometime not, thread one point stuck in my mind as a lowly bottle jockey.

If this "oxide" layer appears as a shunt resistance across the capsule it will not result in a general attenuation but will in fact cause a loss of LF. A capacitor mic capsule system is a high pass filter. To get an aperiodic attenuation you need a shunt CAPACITANCE.

Well! Every other fekker was having a pop!

Dave.