How to fry a microphone capsule

[kingkorg]

Interesting result of an experiment.

I was curious about how far i can really push a capsule regarding polarization voltage. I modded some mics before with up to 100v with no issues, and i was almost getting irritated as the diaphragms wouldn't collapse.
So today i went for 125v with this one, and the thing just kept delivering while sounding just as it should. Until the first plosive came that is. And then BAM! A spark in true ElectroBOOM (youtuber) style!
I managed to spot weld the diaphragm to the backplate, and burn some gold underway. I still can't stop laughing. So i guess diaphragm sticking to the backplate isn't the worst thing that can happen.

 

[soliloqueen]

Try to blow up my k47 I want to see how much it can take

 

[Khron]

I would expect the 3um diaphragms to collapse / zap through even sooner (due to more elasticity and thinner dielectric). Was this a "normal" 6um one?

 

[OPR]

Wow, I haven't seen that one before!
The other problem with using higher than intended polarization voltage is that it restricts the diaphragms ability to move, which in turn affects frequency and transient response.
The fact that the diaphragm initially survived such a high voltage may also indicate that the diaphragm resonant frequency may have been high or the capacitance low compared to a Neumann capsule.
I use a camera lense puffer/cleaner to blast air onto my diaphragms to ensure that they don't collapse at the intended polarization voltage. It's probably worth doing this if you want to experiment with higher voltage.

 

[rogs]

I had an edge terminated capsule which - according to the spec - had a 3 micron membrane. It was certainly quite sensitive, and would function fine with 50v polarisation DC applied.
When I upped that to 60v it would work for a while, and then the output level would drop and become distorted.
Looking at the capsule, and the membrane looked slightly 'dimpled' , with the dimples following the backplate hole pattern. Removed the 60V, waited a few minutes and re-applied the 50V bias..... Worked fine again after that.
So it wasn't exactly the 'spot welding' result that Kingkorg observed, but I think it had at least 'partially' collapsed - but only temporarily?

Since then I've re-used the capsule on one of my RF mics. Only applying 3 or 4 volts of RF seems a much safer option!

 

[Khron]

Kingkorg's experiment led to the bias voltage arcing through the mylar. That's a couple steps "beyond" the diaphragm sticking to the backplate

For all we know, there may have even been a burr on the edge of a hole, that precipitated the process, perhaps managing to ("violently") poke through the mylar upon the higher bias being applied

 

[OPR]

For all we know, there may have even been a burr on the edge of a hole, that precipitated the process, perhaps managing to ("violently") poke through the mylar upon the higher bias being applied

Very likely, or conductive debris.

 

[kingkorg]

Try to blow up my k47 I want to see how much it can take

Not doing that, like it way too much

I would expect the 3um diaphragms to collapse / zap through even sooner (due to more elasticity and thinner dielectric). Was this a "normal" 6um one?

Honestly i have no idea. It's a 35mm one from a TSM mic. ln76d mentioned before he was pushing these quite far and he was right, they can take a lot, 32mm ones as well. Diaphragm tension on these is quite high, and they have center termination so it helps.

I had an edge terminated capsule which - according to the spec - had a 3 micron membrane. It was certainly quite sensitive, and would function fine with 50v polarisation DC applied.
When I upped that to 60v it would work for a while, and then the output level would drop and become distorted.
Looking at the capsule, and the membrane looked slightly 'dimpled' , with the dimples following the backplate hole pattern. Removed the 60V, waited a few minutes and re-applied the 50V bias..... Worked fine again after that.
So it wasn't exactly the 'spot welding' result that Kingkorg observed, but I think it had at least 'partially' collapsed - but only temporarily?

Since then I've re-used the capsule on one of my RF mics. Only applying 3 or 4 volts of RF seems a much safer option!

I have one like that, it doesn't take high voltage either. The edge terminated from Røde NT1 and 797 audio took 100v no problem, and are still operating at that voltage with no issues.


Doug actually mentioned this arcing at about 9 minutes in: