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91
Klaus Heyne's Mic Lab / Re: Nickel vs. gold sputtering
« Last post by Kai on February 26, 2018, 04:22:54 am »
... though that may be unrelated to the metal used in sputtering.
Nickel membranes are not sputtered on Mylar film like it's done with gold, but are solid metal.

Nickel is still indispensable in measurement microphones, because it allows constructing microphones that do much less change their sensitivity with temperature, and having a much greater temperature range they can survive.

If you heat up a mylar diaphragma it loses its tension (even permanent from some temperature point on) and comes closer to the backplate, thus increasing the mic's sensitivity.

Same would apply by some lesser amount to Nickel due to thermic expansion only (opposed to Mylar's material characteristic change), but as the capsules body is built from metal too, this is largely compensated. Permanent changes due to temperature are avoided by pre-aging the capsules in an oven at temperatures a mylar capsule would not survive at all.

For a measurement microphone it's important to be extremely parameter stable over temperature and time, something that cannot be achieved with Mylar.
So if you have a cheap electret measurement microphone, you better not put it out into the sun.
92
Klaus Heyne's Mic Lab / Re: Nickel vs. gold sputtering
« Last post by David Satz on February 26, 2018, 12:34:41 am »
Before tensilized Mylar became available in the mid/late 1950s, Schoeps used nickel diaphragms in all their capsules (e.g. the M 221 series). But all the Western European manufacturers changed over to Mylar as soon as they could, because the resulting capsules are that much less fragile.

At Schoeps after the changeover, whenever any older capsule needed a repair that called for a new diaphragm, they installed a Mylar membrane in place of the nickel one. At one time I owned a pair of M 221 B microphones, and one of my M 934 B capsules underwent this change. After I got the capsule back from repair I made several recordings with the pair before it ever occurred to me that now the two diaphragms must be of different material from one another. I couldn't hear any difference between them, at least in the cardioid setting of the capsules.

All in all, diaphragm material (and also diaphragm thickness) as aspects of a capsule's acoustical design strike me as relatively minor factors in the sound of a microphone, as long as they're within the parameters required by the capsule's acoustic design. A membrane's excursions in response to sound are so tiny, the mass of the diaphragm is swamped by the mass of the air that has to move along with it, and the motion of the air on the backplate side of the diaphragm is constrained by the carefully controlled internal friction within and between the chambers of the capsule. The diaphragm isn't an independent "actor" by any means.
93
Klaus Heyne's Mic Lab / Re: Nickel vs. gold sputtering
« Last post by klaus on February 25, 2018, 06:41:56 pm »
Among speculation why metal diaphragms are not more prominent in capsule manufacturing today (material sourcing problems, lack of manufacturing and assembly skills, long-term thermal stability or stability when momentarily exposed to environmental stresses, etc.) one fact is incontrovertible:

When a micron-thin diaphragm makes contact with an electrically charged backplate, as occasionally happens when high sound pressure or popping occurs, arcing results, which can burn holes into the diaphragm. You can prevent this only by coating the metal diaphragm with an insulating layer. But that may defeat the purpose of using a very thin and agile metal diaphragm instead of a plastic one that usually is twice as thick or thicker than a metal diaphragm.

The other way to prevent arcing would be to put an isolation layer on the backplate. I am not sure who did or does that, but there must be a good reason why this technique is not broadly applied.
94
Klaus Heyne's Mic Lab / Capsule Diaphragms: Nickel vs. Gold
« Last post by Mickeyrouse on February 25, 2018, 09:32:56 am »
Though I have been around mics a long time, only in the last few years have I learned about Neumannís nickel membranes.
What are the comparative characteristics of one versus the other? If they perform the way some posters seem to imply, why did Neumann discontinue them? Did anyone else ( Schoeps, B&K, Neumann Gefell, etc) experiment with them?
  It seems like nickel, at a higher melting point and a higher Brinnel hardness, would be more difficult to work with. And I canít imagine a better conductor than gold. Since so little gold is actually deposited on a membrane,  it doesnít seem like raw material cost would be significant. Judging by some comments here and on other bulletin boards, the longevity of the membranes doesnít seem to compare to more commonly used materials, though that may be unrelated to the metal used in sputtering. And it seems like the nickel membrane surface would be more likely to suffer corrosion fron vocalistí  saliva aerosols.
    Inquiring minds want to know.
95
Klaus Heyne's Mic Lab / Re: 7 Mics for Kim Jong Un - Why? What are they?
« Last post by Mickeyrouse on February 25, 2018, 09:15:26 am »
TWELVE mics- now I AM impressed. Just imagine the potential for phase issues, especially if they're leading to the same input.
96
Klaus Heyne's Mic Lab / Re: Gallery Of Greats
« Last post by klaus on February 23, 2018, 04:28:36 pm »
Hello David,

What you unearthed from the obsolete Neumann Pinboard is indeed fascinating.

As KM56/SM2/SM23 capsules were used in KM88 which were discontinued in the mid-1960s, Neumann must have increased diaphragm tensions on existing capsules in their shop for the last batch they sold.

This would have addressed the on-going issue of arcing holes in these super-thin nickel diaphragms, especially when the mic is used for spoken word: close-up use and consequent 'plosives exacerbate the arcing problem.

It is indeed possible to increase diaphragm tension on these capsules by carefully adjusting assembly components (I have done this), but  it can be hit and miss, trying to dialing in a specific outcome on a metal diaphragm thinner than 1Ķ, so I assume quite a few capsules were trashed in the process.
97
Klaus Heyne's Mic Lab / Re: Gallery Of Greats
« Last post by David Satz on February 21, 2018, 07:23:36 pm »
Klaus, I found the Pinboard messages about the change in the KM 88's low-frequency response. The essential one from Mr. Schneider is PBD_11554, dated Sept. 1, 2003 (i.e. from the original arrangement of the Pinboard, before its active part was divided into three sections).

I don't think it would be right to post the message here without permission, but its essential point is, the diaphragm tension was increased (thus reducing the low-frequency response especially in the figure-8 setting) because this improved operational reliability when the microphones were used for speech pickup in radio broadcasting. He said that this change had been made in about 1982.

--best regards
98
Klaus Heyne's Mic Lab / Re: Neumann KM 88i stuck on fig. 8
« Last post by klaus on February 18, 2018, 05:54:41 pm »
Not at all. This mic is a rare find and requires love and affection from anyone who would dare to dig inside and sort out the pattern switch. Go ahead and make the connection! Just be sure to report back what you found.
99
Klaus Heyne's Mic Lab / Re: Neumann KM 88i stuck on fig. 8
« Last post by Kai on February 18, 2018, 05:50:39 pm »
are you repairing microphones yourself?
Not on regular base like Klaus, just from time to time, and this wouldn't be a problem. I've seen you're located in Swiss, so - I'm in Gemany.
But maybe we're hurting the forum rules, for going on you should PM me, or Klaus.
@Klaus, feel free to delete this posting if necessary.
100
Klaus Heyne's Mic Lab / Re: Neumann KM 88i stuck on fig. 8
« Last post by bicarbone on February 18, 2018, 02:12:18 pm »
Sorry, I meant sending it to Herr Klaus! I don't know, are you repairing microphones yourself? No offense, hopefully.
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