Making a LDC Capsule - Videos

[Whoops]

While searching on the topic to learn a little bit more on how a LDC capsule is made I watched some really nice videos that show the basic process,
sharing these videos with you because I really think in the future capsule DIY will be a thing...

In 2008 when I joined the forum there were no mic projects besides the Gyraf's G7, 12 years after the progress is tremendous.

The 2 first videos are really really good, they are from Soyuz microphones and they show their process:






This is a good video also from JZ microphones:




This one is for the general public but shows some details on how the Neumann U87 is made:




Another nice one from Pearlman microphones:

 

[abbey road d enfer]

sharing these videos with you because I really think in the future capsule DIY will be a thing...

I believe the last major obstacle is making the brass (or plastic or ceramic) parts with enough precision. It takes a precision lathe and a precision hand. I don't see any of the alternative fab resources (3D print, CNC machining, electro-erosion) being capable of achieving this level of precision.
So I think that for a long time, there will need to rely on subcontractors (or cannobalizing cheap stuff).

The 2 first videos are really really good, they are from Soyuz microphones and they show their process:

This is a good video also from JZ microphones:

This one is for the general public but shows some details on how the Neumann U87 is made:

Another nice one from Pearlman microphones:

I can't help noticing how elusive they all are about tensioning. In the second Soyuz vid, you see the guy doing tensioning with a flick of the wrist. Makes me think of how a luthier installs the soul post under the violin bridge.

 

[Gus]

No laminar flow bench?
No gloves?

 

[Whoops]

I can't help noticing how elusive they all are about tensioning. In the second Soyuz vid, you see the guy doing tensioning with a flick of the wrist. Makes me think of how a luthier installs the soul post under the violin bridge.

In all the videos tension seems to be made just by stretching until there's no wrinkles on the Mylar, doesn't seem to go further than that...

 

[Whoops]

I believe the last major obstacle is making the brass (or plastic or ceramic) parts with enough precision. It takes a precision lathe and a precision hand. I don't see any of the alternative fab resources (3D print, CNC machining, electro-erosion) being capable of achieving this level of precision.

Maybe you're right but just only related to the backplate milling.
The Back plate drilling can be done with a CNC with enough precision.
The plastic rings can also be made with 3D printer or CNC also with enough precision for the ring duty.
I think Rode uses CNC a lot, of course they have top notch machines, you can see the factory tour in this video:
https://www.youtube.com/watch?v=EfTfNcnQTqc


The Skin can be put and tensioned by doing a Jig for it, dont think its hard to DIY one Jig for it.

The Gold plating on the Mylar I'm really not seeing how would be possible to DIY.

Overall, as far as I can see if someone gets the Circular Brass for the backplate already machined (but without holes), and if its able to get a Mylar leaf with the gold dots already inserted (like in Pearlman video) the rest of the stuff seem to be not that hard to DIY

 

[abbey road d enfer]

Maybe you're right but just only related to the backplate milling.
The Back plate drilling can be done with a CNC with enough precision.

Agreed. When you see how they do it, with a pedestrian bench drill and a template...

The plastic rings can also be made with 3D printer or CNC also with enough precision for the ring duty.

Maybe. 3D printing is not very accurate, I think some finishing needs to be done.

In all the videos tension seems to be made just by stretching until there's no the wrinkles out of the Mylar, doesn't seem to go behind that...

What accuracy is that?

The Gold plating on the Mylar I'm really not seeing how would be possible to DIY.

I would think it's not the most undoable part. My brother in law (RIP), who was a renowned lens cutter, made his own sputtering machine. I helped by making him a THT supply.

Overall, as far as I can see if someone gets the Circular Brass for the backplate already machined (but without holes), and if its able to get a Mylar leaf with the gold dots already inserted (like in Pearlman video) the rest of the stuff seem to be not that hard to DIY

That's more or less what I suggested, sourcing the real difficult parts.

 

[Whoops]

In all the videos tension seems to be made just by stretching until there's no the wrinkles out of the Mylar, doesn't seem to go behind that...

What accuracy is that?

I don't think there's any accuracy in that, don't you think?
It seems they just stretch the membrane and go with it, I thought the process was a bit more precise and involved a measuring jig to measure the correct tension

 

[Whoops]

Maybe. 3D printing is not very accurate, I think some finishing needs to be done.

Yes, some finishing, but the rings don't need to be micron precise, just precise enough

That's more or less what I suggested, sourcing the real difficult parts.

For the backplates, I see the possibility (hypothetically) that I could buy full Brass round rod, and take it to a local Lathe technician to cut the rod in backplates with the provided dimensions.
There's quite a few small old school shops with lathe machines, that might accept this work.
I just don't know how precise they would be, But I see it being possible.

In the end it's not cost efficient for 1 or 2 capsules, but in a GroupBuy kind of thing it could work

 

[kingkorg]

It seems they just stretch the membrane and go with it, I thought the process was a bit more precise and involved a measuring jig to measure the correct tension

Key thing, Pearlman just mentions, is stabilizing the diaphragm. Exposing it to some heat for a period of time, so it doesn't loosen over time. 

Some diaphragms need  precise tensioning, some not so much. I have re skinned some sdc diaphragms from very loose, to the point of breaking. Almost made no difference. Too tight, you loose some low end, and tighter tends to extend ultrasonic limit, but that can not be heard. Too loose it tends to be extremely sensitive to plosives.

When it comes to metalizing mylar, its simplest to go with edge terminated, and just buy metalized mylar.

 

[RuudNL]

[offtopic]  @kingkorg: did you ever reskin AKG CK1 capsules? [/offtopic]

 

[kingkorg]

Nope, never had the opportunity.

 

[Marik]

No laminar flow bench?
No gloves?

Those you can find at Chinese facilities... including state of art clean rooms))))

Other than that most of the videos make me just chuckle...

-Pre-stretching Mylar and then putting it on backplate so that the mass of (quite heavy) outer ring applied to the stretch???
-Drilling the backplate by hand with template, then putting back in the chuck, facing with hand ground tooling (!!!!!) and then with straight face claiming 2 micron (!!!) tolerances??? At what temperature? Even simple following lapping will change it..
-Somebody could possibly give me insights as for significance of Golden Drop...

... and there are dozens of those inconsistencies...

Obviously, none of the manufacturers would ever tell you 'everything', but such silly marketing BS just doesn't make much sense...

Best, M

 

[Gus]

To add to Marik's post

You need a temp controlled room to as well as good cooling of the part to machine to that kind of tolerance.
I wonder if anyone has tried cryogenic machining for capsule parts?

something to read
https://www.tappi.org/content/events/07place/papers/culbertson.pdf

 

[kingkorg]

Nice video, promotional, but educational as well.

https://vimeo.com/199946849

 

[Marik]

To add to Marik's post

You need a temp controlled room to as well as good cooling of the part to machine to that kind of tolerance.

Besides, the machine needs to be well ‘warmed up’. Before we start any critical machining we run the program for an hour without making parts, so all parts of the machine—spindle, head, table, motors, ways, ballscews, etc. come to a normal working temperature.

Best, M

 

[Whoops]

One more Video from Soyuz, showing other details on making the capsules:

 

[Whoops]

Video showing the U87Ai capsule being made:

 

[flashlamp]

maybe unimat jewelers lathe would help to make one.

 

[abbey road d enfer]

One more Video from Soyuz, showing other details on making the capsules:

Video showing the U87Ai capsule being made:

None of these vids shows how the diaphragm's tension is scontrolled.
It looks like it's just the operator's hand feel at Soyouz.
Neumann just don't mention it.

 

[Whoops]

None of these vids shows how the diaphragm's tension is scontrolled.
It looks like it's just the operator's hand feel at Soyouz.

The last video of Peralman it's a similar way to the Soyouz, it seems they just stretch the Mylar until it's straight and has no wrinkles and they call it a day...
Maybe tensioning is not as scientific or precise as we tought.