Making a LDC Capsule - Videos

[Marik]

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.

Correct pre-aging of the diaphragm and precise tension/tuning have utmost importance in a long term stability and uniformity from unit to unit.

Best, M

 

[Whoops]

Correct pre-aging of the diaphragm and precise tension/tuning have utmost importance in a long term stability and uniformity from unit to unit.

Best, M

Thanks Mark,
I also imagined that, and maybe that's not shown in the videos. But at least what can be seen in the videos is a bit less precise than that.
I would also love to see the tensioning and tunning

 

[pinchemotherloaf]

From what I know and can say:
There is no post 'tuning' or 'tensioning' involved

 

[kingkorg]

"Ageing" is a fancy cryptiic word for exposing the diaphragm to the specific temperature for a duration of time. Skipped on purpose in Pearlman's video. All of which explained in detail in DuPont datasheets for their mylar. Tension is usualy achieved by using weights. Explained in detail on Dale's 10000cows page. Checking resonant frequency of the membrane couldn't be easier, explained very well in ages old threads. Simplest would be to tension it and glue to the capsule ring (k47, k67) and blow gently against it, it will ring at resonant frequency. Medieval techniques guarded by "gurus"

 

[Marik]

Tension is usualy achieved by using weights. Explained in detail on Dale's 10000cows page. Checking resonant frequency of the membrane couldn't be easier, explained very well in ages old threads. Simplest would be to tension it and glue to the capsule ring (k47, k67) and blow gently against it, it will ring at resonant frequency. Medieval techniques guarded by "gurus"

While this technique used by quite a few manufacturers (including Neumann) it is not as precise as tensioning with a threaded tension ring. Also, after gluing the diaphragm and cutting the Mylar off surrounding ring the tension still might need corrected to get to the exact point.

Indeed, blowing, or pinging on the ring the diaphragm is glued to will give you pretty accurate frequency. If you want to be real fancy you could take a generator, connect to a little speaker, make a coupler and then place a little light ball (for example, taken off a silica pack) on the diaphragm and then sweep the frequency and watch when the ball starts 'dancing'...

Best, M

 

[Whoops]

Really nice video showing disassembled Oktava MK-219 and K67 type capsules:

 

[Whoops]

RODE capsule making, very nice, it's the most automated and machine based production line

 

[Whoops]

JZ microphones, capsules tuned by hand:

 

[Whoops]

Beesnees capsule manufacturing:

 

[tskguy]

Love this thread!!!
I will say that everything you guys are saying is correct
One note is that I am still learning this craft. Even after ten plus years of kinda doing it correctly. My understanding and skill has evolved greatly over time. Here some thoughts. A good sounding capsule is a system. The hole size, depth, capacity, space between sides, tuning, gold deposition all matter and impact each other… even the rings matter! Here are some things I’ve learned over the years.. final Mylar tension and resonant frequency for sure matter but maybe not as much that’s speculated on the internet. Mylar source and gold deposition thickness are very important.
the most impact regarding sound is backplate hole size and how deep the blinds are. Another huge impact is the final capacity.. that’s probably number 2 regarding impact in sound. Holding micron tolerance is really only important if you are machining a gap on the face of a backplate. Keeping things clean and oil free are very important but you don’t really need a clean room or laminar flow bench. And making one is easy doing 100s of times consistently is another story!
Eric…

 

[soliloqueen]

Love this thread!!!
I will say that everything you guys are saying is correct
One note is that I am still learning this craft. Even after ten plus years of kinda doing it correctly. My understanding and skill has evolved greatly over time. Here some thoughts. A good sounding capsule is a system. The hole size, depth, capacity, space between sides, tuning, gold deposition all matter and impact each other… even the rings matter! Here are some things I’ve learned over the years.. final Mylar tension and resonant frequency for sure matter but maybe not as much that’s speculated on the internet. Mylar source and gold deposition thickness are very important.
the most impact regarding sound is backplate hole size and how deep the blinds are. Another huge impact is the final capacity.. that’s probably number 2 regarding impact in sound. Holding micron tolerance is really only important if you are machining a gap on the face of a backplate. Keeping things clean and oil free are very important but you don’t really need a clean room or laminar flow bench. And making one is easy doing 100s of times consistently is another story!
Eric…

Hey Eric, quick question: if micron tolerances aren't required if you're using spacers, what flatness would you recommend having for the face of the backplate. Is ISO fine enough, or does it need to be +- what? I haven't made enough at scale to know what I can get away with without inconsistency yet. What's your experience?

 

[abbey road d enfer]

"Ageing" is a fancy cryptiic word for exposing the diaphragm to the specific temperature for a duration of time. Skipped on purpose in Pearlman's video. All of which explained in detail in DuPont datasheets for their mylar. Tension is usualy achieved by using weights. Explained in detail on Dale's 10000cows page. Checking resonant frequency of the membrane couldn't be easier, explained very well in ages old threads. Simplest would be to tension it and glue to the capsule ring (k47, k67) and blow gently against it, it will ring at resonant frequency. Medieval techniques guarded by "gurus"

Checking the resonant frequency is not the difficult part. What's difficult is getting the tension right before gluing. After gluing is too late.
The Rode video shows how they do it with a proper jig, but I suspect many makers tend to use a wet finger approach.

 

[kingkorg]

Checking the resonant frequency is not the difficult part. What's difficult is getting the tension right before gluing. After gluing is too late.
The Rode video shows how they do it with a proper jig, but I suspect many makers tend to use a wet finger approach.

Noooooo! That's exactly why those Røde capsules suck, and get upgraded with hand tuned dirty ones (kidding)

And yet it changes again after "ageing" process.

 

[tskguy]

Hey Eric, quick question: if micron tolerances aren't required if you're using spacers, what flatness would you recommend having for the face of the backplate. Is ISO fine enough, or does it need to be +- what? I haven't made enough at scale to know what I can get away with without inconsistency yet. What's your experience?

So if your lapping them flat a surface plate and some 400 grit is good enough.
you don’t need to worry about the surface relative the the other side if that makes sense…you don’t want them super smooth like a mirror. The surface imperfections actually helps the Mylar not sucking back and getting stuck.

 

[Tim Campbell]

So if your lapping them flat a surface plate and some 400 grit is good enough.
you don’t need to worry about the surface relative the the other side if that makes sense…you don’t want them super smooth like a mirror. The surface imperfections actually helps the Mylar not sucking back and getting stuck.

This will work if quality isn't of any importance. A properly manufactured capsule can be mirror smooth without causing attraction. Even when Neumann placed bumps onto the surface of their K67 capsule it could still collapse when working improperly. High spots, contamination or too low a tuning tension for the membrane compared to polarization voltage are the most common cause of collapse. Roughness is used as an attempt to help the membrane release once it has hit the backplate.

Many chinese capsule backplates are highly polished without problem.

 

[tskguy]

Oh Tim…….
“If quality isn’t an issue”. Lordy my suggestion is coming from the DIY perspective. Go as far as you want regarding lapping. But take a look at Neumann capsules. They have a very slight surface finish. And trust me on this one. It won’t make a bit of difference regarding the sound.
Eric

 

[Tim Campbell]

Neumann beadblasts their capsules as part of their deburring process.
I hope Marik joins in to reiterate his feelings about backplate flatness. Sound quality is not the only factor to consider here. Mechanical integrity is equally important. An uneven backplate will contribute to a membrane collapsing to a greater degree than a polished backplate.

 

[tskguy]

I’m out… I’m too busy actually building mics. Tim and Marik the forums are yours..

 

[Tim Campbell]

 

[Recording Engineer]

I remember Stephen Paul talking about 1999-era(?) 797 Audio k67/k87 -type capsules trying to mimic his 3-micron mod versions. He was actually somewhat impressed and flattered, but his biggest detrimental comment was how rough the backplates were and that was most definitely the start of correction.