Liberty Instruments, Inc.
Making a rugged, connectorized microphone from a Panasonic microphone capsule
You will need the following:
microphone capsule, (either the calibrated units sold by Liberty Instruments or Old Colony Sound Labs, or a Panasonic WM60xx or DigiKey Part# P9959-ND). If you get the uncalibrated capsule, youll need to very carefully solder a pair of limp wires (30 gauge stranded, preferable twisted, is recommended) approx. 12" long to the capsule. The "ground" terminal is the one which connects to the case of the capsule.
brass inline "RCA" jack, obtainable from Radio Shack or other sources
12" long piece of 9/32" round brass tube, K&S Engineering #132. This can be found at many hardware or hobby stores, or from K&S Engineering (312) 586-8503.
Unscrew the sleeve of the inline RCA jack from the connector. Cut off the shield connection clamp of the connector so that it is a small, but still solderable, stub. Drill or file out the smaller opening in the sleeve so that it will allow the brass tube to slide through it. Solder the tube to the sleeve, being sure there is room for the back of the connector to screw back into the sleeve. As both pieces are brass, a standard soldering iron or pen will be adequate. Be sure to let the solder flow a bit around the seam for a good strong bond.
Wrap a layer or two of plastic tape around the circumference of the capsule (or use heat-shrink tubing) so that it wll fit snugly into the end of the brass the tube, feeding the wires down through the tube. Solder the wires to the connector (ground wire to the shield, hot to center contact -- if prewired, the ground wire should be the darker wire). Then screw the connector back into the shell, being sure not to twist the wires off the connector. It may be a good idea to pretwist the wires counterclockwise before engaging the connector to minimize twisting tension -- this will depend on how much slack there is in the wires and on how limp the wires are.
Thats it. It is actually much easier than it sounds. You may have difficulty at first with wire lengths and getting the wires to behave when pushing them up into the tube; but other than this, the entire process usually takes only minutes and the resulting microphone is very serviceable. Its small diameter is great for measurements (it minimizes the effect on the measured sound field), but is too small for standard microphone clips/clamps (for mic stands) without help -- you can wrap a section of the mic in dense foam or cloth to make it fit the clamp.
This mic is designed to be remotely biased from a Liberty Mic/Probe Preamp or a Turtle Beach Fiji or Pinnacle sound card. With proper adaptors, it may also be usable with some other soundcards or devices which provide phantom bias for an electret microphone.
To convert calibration data which is provided at bias conditions of 2.5VDC via 2.2k ohm load (as for the Liberty Mic/Probe Preamp) to that for bias conditions of 5VDC via 4.7K with additional AC load of 10K (as for the Turtle Beach Fiji/Pinnacle direct connection), multiply the sensitivity value by a factor of 1.48. For example, if the first line of your microphone correction data file were to list the reference sensitivity as 6mV/Pa, replace this number with the the value 8.88mV/Pa (which is 6mV/Pa * 1.48).