Soliloqueen's k87(k67) and k47 capsules

[Khron]

severely damaged by oxidation

... of the... backplates?

 

[ZHOUJUN]

Some are oxidized on the back plate, and some are oxidized on the diaphragm coating. This is the most oxidized Neumann K87 capsule I have ever seen, but even though it was so damaged, it still did not produce any noise. I took off the ring again and installed it as it was. It can maintain normal output for a long time, but has a slight disadvantage in high frequency.

 

[soliloqueen]

the type of brass here normally has a protective oxide layer, but if left exposed for a long time it will very slowly darken. next time i have fresh plates i'll show you guys the protective oxide layer forming over 24h. afaik this doesn't affect the capsule's function meaningfully

Here are two early in house test plates that tarnished due to incomplete drying:
One with mild tarnishing:

And one that developed a patina:


This is harmless. These could be lightly polished and skinned provided the acrylic could survive the tarnish remover.

the tarnish highlights how ridiculously stupid good the machining is, so there's that.

 

[ZHOUJUN]

the type of brass here normally has a protective oxide layer, but if left exposed for a long time it will very slowly darken. next time i have fresh plates i'll show you guys the protective oxide layer forming over 24h. afaik this doesn't affect the capsule's function meaningfully

Here are two early in house test plates that tarnished due to incomplete drying:
One with mild tarnishing:
View attachment 141278
And one that developed a patina:
View attachment 141277

This is harmless. These could be lightly polished and skinned provided the acrylic could survive the tarnish remover.

the tarnish highlights how ridiculously stupid good the machining is, so there's that.

As far as I know, these oxides do not have an impact on the sound of the capsule in the early stage, but these oxides will slowly fall off with the vibration of the diaphragm to form very fine powder. In the limited gap, if they absorb the air Dust and water molecules may produce electricity when working arc, which will accelerate the oxidation process of the plate and change the capacitance of the capsule, which will have an impact on the life of the capsule. Therefore, many capsules produced in China that cost tens of dollars have a relatively short life. Due to production cost issues, they do not have back-to-back The board is processed, and some scratches can be clearly seen.

 

[rogs]

A big reason why modern neumann capsules sound worse than the same exact models produced previously is because they kept collapsing from environmental static charge when shipped to colder climates. The ability of mylar to discharge static is reduced as humidity is reduced. Eventually it's reduced below a point where the static can travel into the gold and be discharged. The plastic itself (not the gold, as in correct operation) becomes charged and attaches itself to the backplate. They tried just about every other way to solve this problem, for decades. Tons and tons of anatomical changes to the capsule centered around defeating this issue. At the end, they literally tried putting little dots of plastic on the backplate itself to hold the diaphragm up, lol. Even that didn't work. Eventually they finally gave up and changed the tension and therefore the sound of the capsule. Mine are built to original spec, and I've been thinking about shipping them with a disclaimer card not to store or operate them below 35 or 40% relative humidity.

Here is an unfortunate accurate k47 of mine that encountered 18% relative humidity. This issue you're seeing right here is Neumann's personal white whale:
View attachment 141236

When the diaphragm releases, the sound of the capsule is not always affected, but it leaves telltale damage: tiny, almost invisible circles in the gold where the backplate holes are. The dreaded "neumann capsule stored in a storage unit syndrome" often seen on ebay capsules.

German capsules (and my capsules), use electrical mylar, which has a rough microsurface and consistent mechanical properties. Most Chinese capsules use optical mylar meant for lamination. This has a smooth microsurface and doesn't collect environmental static charge as readily, which is why this issue is almost never seen in Chinese capsules. It also has very inconsistent mechanical properties, which contributes to the difference in sound slightly. This isn't a matter of mylar quality. There's perfectly good chinese mylar out there. It's that they're using film that's produced with the wrong qualities/target usage.

Not a problem I'm likely to encounter with my flat 47s..... They only have around 3 or 4 volts of RF applied across them - no DC polarisation voltage - and they are working at an impdance of only a few hundred Ohms....
Even suitable for LDC mics being used outdoors!

 

[soliloqueen]

Not a problem I'm likely to encounter with my flat 47s..... They only have around 3 or 4 volts of RF applied across them - no DC polarisation voltage - and they are working at an impdance of only a few hundred Ohms....
Even suitable for LDC mics being used outdoors!

This issue doesn't require any polarization voltage at all. It can happen to capsules that have never even so much as been plugged into a circuit just sitting on a table. They don't even need to be metalized. It can happen to the non-metalized side of a single-sided capsule.

 

[rogs]

This issue doesn't require any polarization voltage at all. It can happen to capsules that have never even so much as been plugged into a circuit just sitting on a table. They don't even need to be metalized. It can happen to the non-metalized side of a single-sided capsule.

Sorry, I had misunderstood. I had thought you were describing the problem of the capsule collapsing 'under DC tension' as it were.

The problem of noise caused by high humidity and high impedance is a different one of course, and I have had problems with some capsules collapsing with a high DC voltage applied (not Arienne Audio ones! ).
I had misread your comments as to be problems of this nature.... sorry about that.

 

[amplexus]

This issue doesn't require any polarization voltage at all. It can happen to capsules that have never even so much as been plugged into a circuit just sitting on a table. They don't even need to be metalized. It can happen to the non-metalized side of a single-sided capsule.

This is really good info to know. I have normally stored my ldcs with silica gel in the cases when they’re put away… i guess I should stop that and throw in a 50% Boveda pack!

 

[DFischer]

I've experienced the collapse on at least one of my flat 47s when I first received them. The skin popped back out after I connected the capsule to the PCB, so I didn't think much of it. Arienne, can you take a look at this photo and let me know if it looks like it should be OK? I did some test recordings with it, but I never went crazy trying to check frequency response or polar pattern. I also have it in a studio projects body which you have mentioned that in itself might limit it's potential. I haven't gotten around to test it in another body.

 

[soliloqueen]

I've experienced the collapse on at least one of my flat 47s when I first received them. The skin popped back out after I connected the capsule to the PCB, so I didn't think much of it. Arienne, can you take a look at this photo and let me know if it looks like it should be OK? I did some test recordings with it, but I never went crazy trying to check frequency response or polar pattern. I also have it in a studio projects body which you have mentioned that in itself might limit it's potential. I haven't gotten around to test it in another body.

The sound of the capsule is rarely affected by this problem after the diaphragm detaches. It's just annoying. Here you can see a good example of exactly why Neumann put those little plastic dots where they are on '80s capsules. If you receive a capsule like this, all you have to do is connect or ground and then gently mist above it (Not directly on it). Similar to how you would mist an orchid. Or leave it on the counter while you shower or next to a boiling pot of water.

 

[HerbertR]

The sound of the capsule is rarely affected by this problem after the diaphragm detaches. It's just annoying. Here you can see a good example of exactly why Neumann put those little plastic dots where they are on '80s capsules. If you receive a capsule like this, all you have to do is connect or ground and then gently mist above it (Not directly on it). Similar to how you would mist an orchid. Or leave it on the counter while you shower or next to a boiling pot of water.

Your knowledge is amazing.... Absolutely great what infos you share with us.... biiiiiiig THX

 

[GeorgeToledo]

The sound of the capsule is rarely affected by this problem after the diaphragm detaches. It's just annoying. Here you can see a good example of exactly why Neumann put those little plastic dots where they are on '80s capsules. If you receive a capsule like this, all you have to do is connect or ground and then gently mist above it (Not directly on it). Similar to how you would mist an orchid. Or leave it on the counter while you shower or next to a boiling pot of water.

Ari, this is why both Neumann
companies have put so much effort into the process of pre-aging the membrane.

Much of it is to obtain a consistent level of humidity in the diaphragm to begin with, and then further treatment to minimize the impact of humidity in either direction.

The finished product has a diaphragm moisture level that is part of the manufacturing spec.

 

[OneRoomStudio]

Ari, this is why both Neumann
companies have put so much effort into the process of pre-aging the membrane.

Much of it is to obtain a consistent level of humidity in the diaphragm to begin with, and then further treatment to minimize the impact of humidity in either direction.

The finished product has a diaphragm moisture level that is part of the manufacturing spec.

How does a material have a moisture level unto itself? Wouldn't it be subject to the humidity of the environment it's in? Unless they've found a way to overcome osmosis...

 

[GeorgeToledo]

How does a material have a moisture level unto itself? Wouldn't it be subject to the humidity of the environment it's in? Unless they've found a way to overcome osmosis...

The film has a given moisture level as a result of manufacturing and storage. Starting with film that has any random level of moisture yields unpredictable tension in the field, and possibly uneven tension across a diaphragm.

Part of achieving field stability for capsules in regards to tension is to make sure all of the film has a specific moisture level to start, then to start a slow drying process so that there are no areas of irregular moisture and resulting irregular tension in the final product. The process also helps get curvature out of the film. Having the film within spec before gold evaporation helps achieve a product that has less drift in the field.

 

[OneRoomStudio]

The film has a given moisture level as a result of manufacturing and storage. Starting with film that has any random level of moisture yields unpredictable tension in the field, and possibly uneven tension across a diaphragm.

Part of achieving field stability for capsules in regards to tension is to make sure all of the film has a specific moisture level to start, then to start a slow drying process so that there are no areas of irregular moisture and resulting irregular tension in the final product. The process also helps get curvature out of the film. Having the film within spec before gold evaporation helps achieve a product that has less drift in the field.

I see, you’re talking about the moisture level during manufacturing. There’s nothing that can be done to set the moisture level once it gets out into the world though (other than keeping the environment at a specific humidity level).

 

[GeorgeToledo]

Having consistency of film humidity means that the inevitable loosening effect of vibration cycles and moisture/dryness cycles can be taken into account more accurately, to keep the diaphragm from bottoming out or losing tension in the field.

If the film humidity is not even across capsules as they are made, then the amount of tension shift in the field is more likely to be outside of acceptable tolerance for some units. Further, if it is not even across the surface of an individual capsule itself, you can wind up with side effects such as wrinkles.

I think there is also some molecular and mechanical function of the film being humidified then taken into the direction of drying/tightening that tends towards less loosening.

 

[soliloqueen]

i bought a humidifer so that i could test all the k87s without risking damaging them and it took like days to get this parched air up to a level where handling the capsules is safe. i should be able to resume shipping now. Gonna sprint through most of the remaining orders this weekend