leswatts
Well-known member
Hi
Has anyone measured or seen noise data on passive dynamic/ribbon mics? Generally, it's considered too low to spec on commercial products.
I would expect there to be two basic noise sources:
1) the electrical johnson noise of the real part of the mics electrical impedance
2) the transformed pressure noise of acoustic resistances (often called brownian motion noise)
From my studies the self noise of typical powered condenser mics dominates when using a 1nV/sqrt Hz preamplifier. I suspect that is not the case with passive microphones (with a very quiet room).
An interesting complicating bit is the fact that the electrical impedance is a function of the acoustic environment! As an example, some specialized passive microphones I designed last year change their electrical impedance (at certain frequencies) by 4 times or more depending on distance from an acoustic reflector. Therir electroacoustic efficiency is unusually high though.
Les
L M Watts Technology
Has anyone measured or seen noise data on passive dynamic/ribbon mics? Generally, it's considered too low to spec on commercial products.
I would expect there to be two basic noise sources:
1) the electrical johnson noise of the real part of the mics electrical impedance
2) the transformed pressure noise of acoustic resistances (often called brownian motion noise)
From my studies the self noise of typical powered condenser mics dominates when using a 1nV/sqrt Hz preamplifier. I suspect that is not the case with passive microphones (with a very quiet room).
An interesting complicating bit is the fact that the electrical impedance is a function of the acoustic environment! As an example, some specialized passive microphones I designed last year change their electrical impedance (at certain frequencies) by 4 times or more depending on distance from an acoustic reflector. Therir electroacoustic efficiency is unusually high though.
Les
L M Watts Technology