Building capsules

[burdij]

I have started to build a mike capsule. Its an edge terminated type, hopefully cardioid in pattern, and a single diaphragm. Here are some pictures of the parts:

Now I am waiting for the mylar to arrive.

 

[SSLtech]

You are my new hero.

No seriously. -I adore when people go to this degree of DIY.

More power to you!

Keith

 

[dale116dot7]

Are you using a centre chamber or do some of the holes go all the way through? It looks as though there might be a nice brightness - it looks like you are slightly less damped than an AKG C12, but a lot more damped than most K67-based parts. How deep are your holes? Looks like nice work!

-Dale

 

[gyraf]

:thumb: :sam:

 

[Bauman]

Killer!! :thumb:

 

[burdij]

This is not chambered. I took the pattern from a C12-like (chinese) capsule. There are holes that go all the way through in the first row at 1,3,5. In the second row the through holes again start at 1 so the pattern of through holes is a grid on .2 in. spacing. The depth of all the holes is drilled to 4mm. The diameter of the hole is .050 in. I noted that on the TLM103 capsule and some of the C12 capsules that the number of holes in a row was less than your average Chinese clone capsule so the undrilled surface area is higher. I am curious as to what effect this will have.

 

[Gus]

I have not seen a china C12 like capsule.

I have seen non center screw u67/87 type china capsules.

Is there a china capsule like a CK12?

The machine work looks nice. How flat can you face the metal in the lathe?

 

[dale116dot7]

I've seen a Rode mic with this sort of design, and Peluso offers one that looks a lot like it, too. But not so much in the 'mainstream' Chinese mics from what I've seen. The only thing CK12-like is the edge termination. The 'real' CK12's are acoustically very different in design, despite the fact that they look similar. There are four plates and five air cavities in a CK12 design, and if you thought a piano was difficult to tune.... I tried building one.

Could you post a photo of the backside of the backplate?

-Dale

 

[Tim Campbell]

Keith,

I had no idea you were so easily impressed.

Take that

and that

and that

and that

and that

and just for good measure

[/img]

I'm sure I'll think of some others.


Seriously though, it's hard to make one capsule and have it turn out as good as you had hoped. I think of it as a process.

There are some other guys here who do wonderful work in this area. Dale, Badger (Andy Lawrence) and Marik. I'm sure there are also others that I'm unaware of.

 

[Gus]

Dale

I have a few rodes with capsules like you posted a old ntv(not ntk), nt1000 some caps changed, K2 (tube type changed and caps changed)

The ntv sounds OK I think more to do with the electronics and grill
The nt1000 even with better caps has to much highs
The K2 seems to have the capsule tuned a little different not bad

I have an MBHO CK12 type capsule the rodes don't sound like it.

Tim

I have been thinking about building a capsule like the top one in your post I remember the picture of the back from a post sometime ago. FWIW it looks like the GT44/33 cardiod capsule uses the same idea there is a materal at the backside that looks like its density is tuned via pressure to adjust the pattern.

 

[SSLtech]

Tim,

You've been an icon at my shrine for several years now...

Don't think you're off my radar, buddy!

:green:

Keith

 

[dale116dot7]

Yea, the thing that fools you is the front of the capsule kinda-sorta looks like a CK12 but the guts are nothing like a CK12. More like an edge-terminated K67. Looks like Tim has been busy with that design type. I've been going in a different direction with my capsules.

I totally agree with Tim. I've built about 15 different capsule designs. A few sound pretty good, one or two sound very good, and most of them sound pretty terrible. I always find that I make one that sounds ok, then I want to adjust the sound a bit, so I make another that I think should make the sound go the way I want it. But then it sounds like a telephone.

I haven't really had a chance to play with a 'real' CK12 - only the later ones made of nylon.

-Dale

 

[Marik]

[quote author="dale116dot7"]Yea, the thing that fools you is the front of the capsule kinda-sorta looks like a CK12 but the guts are nothing like a CK12. More like an edge-terminated K67. Looks like Tim has been busy with that design type. I've been going in a different direction with my capsules.

I totally agree with Tim. I've built about 15 different capsule designs. A few sound pretty good, one or two sound very good, and most of them sound pretty terrible. I always find that I make one that sounds ok, then I want to adjust the sound a bit, so I make another that I think should make the sound go the way I want it. But then it sounds like a telephone.
[/quote]

Hahaha!!!

Let's talk about that!!! :twisted: :twisted: :twisted:

I started with LD cardioids of C38 type. Out of 5 one was OK, meaning it would not cut my ears. In fact, I remember there was something nice about its sound... I just never could get a higher output out of that.

Then I turned to SD "true" pressure omnies, as those are easier and actually are fun. I made quite a few experiments with those, finding relationships between different dimentions and skinning them with 3um aluminum and 2um steel foils, and actually was very close... but then it was Christmas and then we bought a house and then we were moved in up until a few days ago...

Yeah, with capsules you think you are very close and then make the one which in your mind has to be the very last... just to realize it sounds like crap :evil:
Oh, well....

I can only imagine the Neumann crew, where today first machinist drills one set of pattern, second machinist drills another set, third... and so on.
Tomorrow we listen to it and then first machinist drills the same set of pattern, but slightly deeper, second... in short, you got the point.
And that is for the whole year long :shock: .

 

[burdij]

Here is a photo showing the back of the capsule and the C12 style capsule I am using for ideas.

 

[dale116dot7]

Are you planning on putting two halves together or just the one? If just one, there are a couple of things you might find. One thing is you might need to block off some of the holes in the back - you'll need to experiment. I usually use the thick 3M 'Post It' plastic file tags for this, although electrical tape works well for this function. Also, you may find that you need more phase shift - you can see this on a lot of cardioid mics - dummy diaphragms or plates with offset holes in them. The TLM103 is a good example of the plate with offset holes. The M7 accomplishes the phase shift by the dimensions of the through holes (which are 5,65mm long and 0,8 mm in diameter), and by the second (dummy or unconnected) diaphragm.

Have you taken apart the blue capsule?

 

[ioaudio]

very nice work! will you use aluminium mylar for the membrane?

 

[burdij]

dale - I am going to try just one at first. I thought that some of the holes would have to go. Although you can't see it in the picture, on the C12 capsule, there is actually a diaphragm of clear mylar on this side of the capsule (the back). I did notice on the back of the TLM that there is a brass cup covering the back of the backplate. This cup has about a third of the holes I have in the experimental capsule. The pattern of holes looks vaguely like an "N". It also appears that the holes in the TLM backplate are drilled all the way through to the cavity. I haven't disassembled it to see, though. On the blue capsule, I wanted to get some frequency response info before sacrificing the capsule on the altar of science. I am fairly sure that it doesn't have any internal chambers except for the one formed by the spacer holding the two sections apart.

io - no, I am planning to deposit gold on 6 micron mylar (if it ever gets here) with this:

An old electron microprobe, sans optics. There is a diffusion pump in back of the mechanical pump.

The hearth with the tungsten boat. You can see the home made high current feedthroughs.

 

[Tim Campbell]

I'm afraid I agree with Dale. Too many holes in your backplate. You might end up with a quite" nasally" or over bright sounding capsule.

Are they through holes or do you have an offset plate seperated by a shim to form a delay network.

If your holes go all the way through and you have no back membrane you could probably achieve a cardiod pattern with as few as two .6mm holes drilled directly from the backplate out through the back. This is a network type that I use when I'm checking other aspects of a design with one membrane.

Good luck with the deposition. Dale's got a lot of experience in that area.
I on the other hand gave up on trying to make my own membrane material. After about 5 years of begging , pleading and grovelling I finally was allowed to buy a roll of original NOS AKG membrane material. Not cheap but beautiful stuff.

 

[ioaudio]

yes, yes, yes - thats the real thing!
i was bidding on vakuum evaporators on ebay but wasnt lucky yet...
but i already have lots of 6µm mylar already...
i bought it here: http://www.wes-technik.de/English/foils.htm very quick&nice service...

 

[Gus]

last time I was looking for a good used industrial vacuum chamber and evap system I saw one was about $18,000. It was too big for my house.

I was thinking about sputtering a system one can be home made but I don't know how clean it would be. An old Scientific American had writeup for a homemade one (late 60s early 70's?)