Microphone Characteristics and Specifications Audio Days 2011 Paris David Josephson Josephson Engineering, Inc. Santa Cruz, California

A bit about standards in the beginning... US ANSI, DIN, European and UK national broadcasters how standards work today measurement standards legalisms

IEC is a measurement standard, not a performance standard no manufacturer uses all of it

Basic electrical specifications sensitivity – determines preamp requirements noise level – quieter than recording ambient level? impedance – does the cable and preamp affect signal? power requirements – can the preamp supply?

Sensitivity millivolts per pascal (mV/Pa) Microphone TypeSensitivityPreamp Gain Needed for +4 dBu Modern dynamic and ribbon, some condenser mics with transformer out 1 – 3 mV/Pa dB (more for quiet sources) Modern condenser mics10-20 mV/Pa dB High output condenser mics mV/Pa dB

Impedance actual source impedance minimum load impedance balance

Noise level “A”-weighted vs ITU-R BS.468 rms average vs quasi-peak why the number isn’t enough

Power Requirements IEC phantom power “the feeble phantom”

Frequency Response under what conditions? –direction –distance –sound source geometry tolerance? smoothing?

Proximity effect not only bass boost up close, but bass rolloff at a distance disappears when there is no gradient (at 90º)

Midrange and HF characteristics midrange often associated with pressure gradient venting or diaphragm resonance high frequency variations often due to scattering...and we’re still only talking about on- axis, anechoic response

Time-domain characteristics mostly affect high frequencies reflections from grille resonators to boost HF response

References