Moke ~ thanks for the response.
Here are the specs for these mics (as stated at Core Sound's website):
The Core Sound Stealthy Cardioid microphones have a frequency response of from 40 Hz to 18 kiloHertz. They have a slightly rising frequency response over that range with the exception of a slight (2 dB) peak between 9 kHz and 12 kiloHertz and a bass response fall off of roughly 6 dB per octave starting at 100 Hertz. (The bass response is very similar to our Core Sound Binaural microphones' with the bass roll-off filter).
We match the microphone pair to within one dB of each other. One of our modifications alters the microphone's sensitivity to approximately -70 dB (0 dB = 1 Volt per microbar), making them ideally suited for recording extremely loud sound sources without danger of overloading your mic pre-amp. This very low sensitivity makes these mics less suitable for recording quiet sound sources. The microphones have a cardioid pickup pattern, rejecting sounds that are 90 degrees off-axis by at least 6 dB and at 180 degrees by at least 20 dB (measured at 1 kHz).
Thanks to our modifications, the microphones have an undistorted dynamic range of over 90 dB, compared to the unmodified capsules' approximately 60 dB dynamic range. They will handle sound pressure levels of more than 138 dB. They are designed to operate into a nominal impedance of between 4.7 and 10 KiloOhms. (If you need other impedances, please contact us.) Their self-noise level is approximately 35 dBA. This is far below the ambient noise level at concerts. (Note that the self-noise specification also makes these mics not especially suitable for recording very quiet sound sources.)
The Core Sound Stealthy Cardioid microphones require a bias voltage that is supplied by its accompanying battery box, the same that is supplied with Core Sound Binaural "battery box" microphones. Powered by a standard 9 Volt alkaline transistor radio battery, the box also contains associated electronics (top quality metallized polypropylene capacitors hand matched to 1%, and 1% metal film resistors) and a high reliability, US-made locking multi-pin connector. The battery box itself is roughly half the size of a cigarette pack, is made of sturdy die cast aluminum, and is finished in a durable black crinkle finish. The battery lasts approximately 500 hours and should be replaced at least once a year. The output to the recorder is a mini stereo phone plug; other connectors can be supplied upon request.