diy mic capsule

[Tim C]

Bob,
Have you used this emachineshop?
How're their prices,quality, turnaround etc?

[adrianh]

orson
Yes me too but I bet you can call those guys.
But as you can see the URL has nothing to do with
p o r n.

[Big Bob Goat]

Tim:

I haven't used them for any machining but have used their software to price an item. You draw what you want machined, send it in and get a price. Really quick and easy.

Like most machine shops, however, it's not cheap to produce anything in small quantities.

It's an interesting concept.

[thomasholley]

I just got a sample of 0.25mil aluminized PET from Sheldahl. I am collecting up materials to join the frey and see how hand making a capsule comes out.

This whole process is very interesting and enlightening to an old hack like me. I should have more raw materials in a week or so, until then the research continues.

One question I have is regarding capsule diameter. I see 32mm and 34mm often. The DYI articles mention 1" diameter. I can understand some of the issues regarding capacitance of the diaphram with regard to the backplane and resultant frequency and resonance issues that arrize as a result of mass, tensioning, etc. Detailed annalysis is certainly beyond the scope of the forum so I guess some general guidelines would be most helpful.

Things like how big is too big? What is not big enough? What materials are best to use for DIY applications?

Lots of thought and experimentation has gone into many of your projects. It is easy to see the care and pride you have in your work, even if it does not always come out exactly as you hoped, you still are willing to share your experience so the next guy gets a boost.

Thanks
Thomas

[toneyr]

I was eating some Pop-Tarts when I noticed the wrapper they were in appeared to be made of a very thin metalized film. I have no idea how thick it is or what the metal is but...

[Tim C]

Toney,
I'm sure that film's too thick. i have a meeting with Shendahl on the 18th to talk about film.

[gus]

Has anyone tried the new RODE K2 or NT2000? The capsule is now made by them I wonder what it sounds like or is modeled after.

[slash14]

Hi everyone !
This is my first post on this great forum, and I'm planning to build my own capsule too.

I'm currently getting some materials to make the membrane and backplate, and here is what I found:
- for membrane metalization and backplate, what about using aluminium ? As most people knows, aluminium is lighter than gold. A sheet of aluminium is about 15µm I think. But as it is lighter than gold, it can be interesting to test with.
- about the membrane itself, what are the mains mechanical differences between mylar and cellophane (I'm not sure of the temr I'm using, infact, I mean the thin plastic sheet that you use for your food). Cellophane is really thin but can be easily deformed and I don't know much of that about mylar.

What would be the best solution in your opinion among the 3 following ?
</font><blockquote>code:</font><hr /><pre style="font-size:x-small; font-family: monospace;">=================== &lt;-- cellophane
----------- &lt;-- aluminum
=================== &lt;-- cellophane
| |
******************* &lt;-- backplate


OR


=================== &lt;-- cellophane
----------- &lt;-- aluminium
| |
******************* &lt;-- backplate


OR


=================== &lt;-- cellophane
----------- &lt;-- aluminum
===== ===== &lt;-- cellophane
| |
******************* &lt;-- backplate
</pre>[/QUOTE]In my opinion, the first solution is the easiest to build.
Second one is lighter than the first one but you must use some glue which add some weight to the membrane ...

Last one must be better for the condenser effect as there is no cellophane between membrane and backplate but seems to be hard to realize.

Last question: I can't see the pictures of Perki's capsule, links seem dead. Is there a mirror link to these pictures please ?

THX for all your answers guys !

[gus]

Most capsules use 6 to 3 micron PET film, one name is mylar. The amount of gold or other metal deposted is measured in angstoms. IIRC I read 100 angstroms of gold in a AES book.

Often a a very small secret amount of a type of metal is deposted first then Gold. I don't know what it is yet. Companys that build good capsules do not tell.

1 micron is .00004 of an inch, hair is said to be about 100 microns.

I believe the near IR part of the light starts at about .9 microns.

One thing about Al it is not maluable(sp) like gold. It also oxidizes fast.

[Tim C]

Slash,
There's no reason to try and re-invent the wheel.If you search this forum you'll find a lot of information about the easiest way of building a capsule and what materials are best and easily available.

Plenty of mics are manufactured using aluminum metalized polyester without problems from stiffness or oxidation.

No microphones are manufactured using a sandwiched membrane(too heavy) or a membrane made of a really elastic substance such as cellophane(wouldn't retain a stable air gap over time).