This is a newer capsule creation, a multi-chambered capsule built using the AKG original CK12 patent for measurements. No audio files yet, but so far it sounds pretty good. I built three pairs of plates, the ones shown are 170 micron gap, the ones in the mic are 220 microns, which is close to the dimension of 200 microns shown in the AKG/Siemens patent. A 40 micron spacer is used between the capsule halves. This spacer is used to tune the frequency response, and I have not taken the time to adjust this carefully yet. Manufacturing of this capsule type requires careful attention to bonding the backplate brass to the outer plastic part. Without actually tooling up for manufacturing, this is somewhat of a time consuming capsule to build. It takes probably 20 hours of machine time to build this capsule.
This is a newer chambered capsule prototype. Centre termination was used to make it easier to manufacture. The downside to centre termination is that you need a round metalized spot on the diaphragm - you can't use premetalized films. On the plus side, a lathe that is not perfectly aligned will not affect the response too badly. The diaphragm will still be the correct distance above the backplate as the centre support tends to compensate for a tent shaped cut. Note that the size of this 'tent' can only be maybe 20 microns or so before it does get to be a problem.
And this is the start of a new attempt. The capsule shown above had good bass and midrange response but was somewhat sibilant. To correct this, a new set of backplates are being made with fewer holes behind the diaphragm (88 instead of 108). The other changes are to the chamber plates. The new plates were drilled in one pass, so the alignment of the holes is much better. Also, the chamber plates have less damping, and will rely on adjustments of the middle chamber for damping, rather than the number of holes. This makes it easier to make a bunch of parts then tune them later. The new capsule parts shown below will also be a dual-diaphragm design.
This is the capsule made from those above parts. Still a bit of sibilance that I don't like. Likely thing is I probably need to raise the bass by opening up the middle chamber area a bit. That's a small tweak for another day.