Studio 939 — Home. Debenham-StereoCondenser.pdf. Diy mic capsule - Page 3 - RECORDING.ORG. Debenham, Stebbings, and Robinson Capsule. This is a Debenham, Stebbings, and Robinson capsule. It sounds very nice and is not very fussy as to diaphragm tensioning. Recommended for a first DIY. Outer plastic is Delrin. To stick it to brass, you MUST use Loctite 770 primer followed by the thinnest cyanoacrylate you can find. Even that may not work correctly. I need to work on finding a better material.
DIY Audio Stuff. First, I must mention the best DIY pro audio board on the web, "The Lab" . My projects are/have been: Neve 1290 clone RCA BA31A clone My own preamp design Gyraf G1176 Jensen JE990 discrete op-amp - built one. It works. Fairchild 660 rough clone - I built it by following half of the 670 schematic but substituting some tubes. LA4 rough clone - improved audio path, high-speed opto compression mode - haven't finished it yet My own SSM2081 feedback compressor design Neve 2254 Compressor - nice compressor.
Gates M6629 Modifications. Figuring out how the Lexicon ARU chip works. Some of my observations on reverbs Processing on some reverbs I like This part is not for the faint of heart..... but if you want to build your own microphone capsules, here are a lot of bread crumbs here to help you along. Vacuum Evaporation for microphone diaphragms Some Strange DIY Capsules Other Capsules (Not mine) . DIY Copper Tube Mic . Making the M7 copy capsules . Debenham, Stebbings, and Robinson mic capsule . These are photos of my DIY tube microphone. These are photos of my DIY tube microphone. Details? The capsule is my attempt at duplicating a Neumann M7 capsule. The capsule uses a glued-in diaphragm (like the M7) but made of 6 micron mylar (unlike the M7's 10 micron PVC material). A gold coating of somewhere between 50 and 150 angstroms has been applied to the film (I do that too).
Making an M7 Copy. This is a photo of tensioning the diaphragm. This is just a photo shoot - the diaphragm in question was wrecked by careless application of glue. A glued diaphragm is attached by gluing the underside of the diaphragm to the capsule and it's easy for the glue to wick underneath the diaphragm and ruin the works. This diaphragm met that fate, but was recycled to show you how I tension the diaphragms. A mass of 120 grams should result in a diaphragm resonant frequency of about 950 Hz. Care must be taken while mounting the diaphragm to the mounting ring to ensure even tension distribution. I have found that usually the diaphragm ends up working well if this is done. The Neumann style capsule is tuned this way at the factory. And this is CNC drilling of the capsule.
And here are six capsules, tested, and ready to go. Photos of deposition system. Photos of my vacuum thermal evaporator. This was the first run. I only set up one target (diaphragm) for this run. I currently have space for seven targets at once. This photo is of the inside of the chamber. The brass clamps hold a small tungsten heater (boat) where nickel or gold wire is placed for the evaporation. This is the evaporation in progress. The heater current is controlled to maintain a target temperature of around 100 to 150 degrees C. A completed diaphragm. This is the bottom side of the evap system so you can see... Cold water goes through the cold cap, then the diffusion pump cooling coils. Since this photo, I've added a PLC to sequence a bunch of valves, and some relatively expensive high-vacuum valves.
Film Vendors. This is a photo of tensioning the diaphragm. I've updated my process a bit so there are more things to show.... This is a shot of a lathe machining the 'final cut' into a capsule. This is a critical cut - there are features on this cut that must be with about two microns (around a tenth of a thousandth of an inch). The early capsules, and carryover backplates from earlier batches, are machined manually. New production is done with CNC control of the same (Sherline) lathe. I am using a Levin Lathe machinable 8mm collet to hold the part - a normal jaw-equipped chuck will not work. This is underneath the cover of the gold coating machine. The heater filament (commonly called a boat) is shown with a small bit of gold wire in the middle. Here you can see the glow of the filament. Things have to be clean. The diaphragm needs to be primed for glue. After placing the diaphragm on the capsule, a quick check with the air gun is used for two things. A small hole is made in the middle of the diaphragm with an empty insulin syringe.
Chambered Capsules. 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. This is a newer chambered capsule prototype. And this is the start of a new attempt. This is the capsule made from those above parts.