Construction tips:

• When building the circuit make sure to shrinkwrap all bare leads to prevent the possibility of shorting against the chassis or other leads. If shorting occurs, your mic won’t work. Shrinkwrap is available from any electronic supply store.
• After you connect the wire leads to the mic cartridge seal the entire back of the cartridge with non-conductive epoxy making sure to overlap a touch where the back meets the sides. This seal provide additional dampening of the phenolic backplate of the capsule which further extends its low frequency response.
• You can mount the cartridge just about any way you want. I chose to mount mine in the end of the rubber boot of a Neutrik XLR connector (see photos). This allows for a compact package, reasonable sonic neutrality, and perhaps even a touch of shock-mounting because of the rubber’s ability to dampen vibration. If you choose to mount your cartridge the same way, sink it by pressing gently on the edges of the cartridge. Do not mash down dead center or you risk damage to the diaphragm. Note that mounting the cartridge this way will also require that you handle the finished mic with care so as not to damage the exposed capsule.
• Buy or borrow a simple multi-meter for use during construction. Mine is an inexpensive Radio Shack model 22-802 which costs about $25. Use this to check all solder points as you go just to make sure that they are good (sometimes a connection may look good, but, for some reason, won’t be making solid electrical contact). By checking as you go you can identify a problem when it occurs rather than having to go through the entire, completed circuit to find a single cold joint (which can easily become a hair-pulling experience!).
• For my power supply chassis I used a single-wide electrical junction box which cost me 79-cents at Home Depot. The solid cover for it (to complete the enclosure) cost another 35-cents complete with screws! This is an excellent choice because it’s cheap, it’s metal, it’s sturdy, and the punch-outs are already the right size for most XLR panel mount connectors. I used Neutrik XLRs which required that I file four grooves around the edge of the hole for the right fit, but the hole was already there!
• Work slowly! This is not a complicated project, so it won’t take long. Check and recheck your progress. I know it’s easy to get impatient and want to have it done, but work methodically. When you are finished the mic will give you years of excellent performance!

Using your new mic(s):

Despite the fact that these mics are omnidirectional they do possess directional characteristics at higher frequencies. Therefore using a pair in an X-Y configuration can yield an incredibly natural stereo image. This also allows you to back-off the top-end a touch (acoustically!) by simply pointing the tip of mic 90-degrees from the source. The impulse response and realism remain unaffected!

These mics are awesome for stereo recording. Try them as drum overheads and room mics. Jecklin-disc and spaced-omni stereo techniques also work fabulously. They are great for acoustic guitar, piano, percussion, choral groups, or just about anything that you want to sound like “being there”.

If you have never used omnidirectional mics before, be aware that they hear much more of the room in which the source is recorded than cardioid mics do. Therefore, if you want a “dead” sound, you will need to either record in a “dead” room or use baffles and/or strategic placement to reduce ambience. I was able to effectively control the ambience in a vocal track by placing the mic below the singer’s head in a carpeted room, pointing up at him while he sang down at the mic. Since his voice projected primarily into the carpet, much of it was absorbed leaving very little to reverberate in the room.

Also, omnidirectional mics do not exhibit the proximity effect (low-end boost when used up close) that directional mics do, so you can place these mics extremely close to a source without the unnatural boominess that can result from using a cardioid. This also means that when you want that low-end effect (for say, a lead vocal) then you will need to dial in a touch of low-frequency equalization.

Because these mics sound so natural, they are great for capturing just about any good-souding source. Use them on guitar cabinets, acoustic instruments, brass sections, ensembles, inside kick drums, you name it. Experiment and have fun!

A word of caution: NEVER connect these mics to a phantom powered input without first turning off the phantom and allowing 5-10 minutes for discharge. Though it is designed to drive a balanced input, the mic’s output is not a true balanced design, so the DC-voltage provided by phantom power on pins 2 and 3 will not cancel as it would with a balanced mic. This could easily damage the cartridge, which is rated for a maximum of only 10-volts DC!

Many thanks to Phil Rastoczny for writing the article on the Realistic PZM modification that is the basis for this microphone. r