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[jamesh]

Hi All,

This is my first post on this forum. I have a pair of KM54s in very good condition (serviced by Gunter Wagner). I used them on a session last night about 1m above a pair of congas. I was playing the congas and while I don't hit/slap conga skins particularly hard, congas are of course considered a high SPL drum.  I've read a few posts on this forum that discuss the vulnerability of KM54 diagphrams to arching at high SPL - but I forgot about this when I put them up last night.

So my question is, was this placement unwise? Also, does arching happen gradually (ie, slowly degrading the capsule over time as its exposed to cummulative arching), or does the capsule die immediately following an instance of arching? The mics sounded fine to my ears the whole way through the session and were still sounding fine when I put them away.

Thanks in advance for your time and comments
James

[klaus]

No one in his right mind would probably make an experiment to test whether an original Neumann nickel diaphragm gets immediately damaged from the electric arc caused by momentary discharge between metal diaphragm (conductive) and electrically charged metal backplate (conductive).

The more likely scenario how arc holes are burned into the super-thin nickel diaphragm: someone blows into the mic at very short distance ("testing, one two... blow blow...") or the mic is exposed to strong wind. The nickel capsules are fragile, compared to plastic membrane capsules, but not that fragile.

I therefore cannot imagine that the diaphragm excursion generated by the sound pressure from a conga would trigger contact between diaphragm and backplate, and subsequently cause an arc burn/hole in the diaphragm.

[jamesh]

Thanks Klaus, Gunter would have mentioned if there was any evidence of arching on the capsules in a recent service. So if at next service the caps have signs of arching then I guess I'm the guy who's unwittingly provided an experiment of sorts! But if the danger is associated with air gusts rather than SPL per se, then as you say I should be more than fine.
Much appreciated
James 

[duskb]

Hi All,

This is my first post on this forum. I have a pair of KM54s in very good condition (serviced by Gunter Wagner). I used them on a session last night about 1m above a pair of congas. I was playing the congas and while I don't hit/slap conga skins particularly hard, congas are of course considered a high SPL drum.  I've read a few posts on this forum that discuss the vulnerability of KM54 diagphrams to arching at high SPL - but I forgot about this when I put them up last night.

So my question is, was this placement unwise? Also, does arching happen gradually (ie, slowly degrading the capsule over time as its exposed to cummulative arching), or does the capsule die immediately following an instance of arching? The mics sounded fine to my ears the whole way through the session and were still sounding fine when I put them away.

Thanks in advance for your time and comments
James

Those diaphragms are very sensitive to plosives to the point where I do not use them for close micing very percussive material (in fact I have tried them on snares and conga's before and always ended up changing them out). I think it had less to do with concern to the capsule material than it did with the concern of 'popping' during the performance, ruining a take. This isn't to say you can't use them for this task but I usually turn to something less sensitive. Further back (like drum overheads) you should be fine.

They sound great close in on acoustic instruments with less transient material.

[David Satz]

No humanly bearable sound pressure will force a membrane against the backplate; it's mass air movement that does this. For these irreplaceable capsules, a windscreen should be used whenever there's any risk.

[Kai]

I've read a few posts on this forum that discuss the vulnerability of KM54 diagphrams to arching at high SPL - but I forgot about this when I put them up last night.

Check the recording - if arcing had happened (I very much doubt) this would be very clearly audible as loud pops in the recording.

Regards
Kai