J.J. Blair wrote on Fri, 03 September 2010 22:03 |
"Noise typically -120dB EIN"
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Yes I saw this in Manley's specs. But how this translates in a equivalent acoustic noise in dBSPL (or A-weighted in dBA) as given by all the other microphone manufacturers?
The sensitivity specified by Manley is 17 mV/Pa, that is -35 dB re. 1V/Pa. Then we must know the electric noise level at the microphone output to get from here an acoustic noise at the microphone output. If it it
x dB re. 1V, then the equivalent acoustic noise level equals
x + 35 in dB re. 1 Pa and
x + 35 + 94 in dB SPL. I don't think that
x equals -120 dB (or -122 dB if the Manley figure is not in dB re. 1V but in dBu) because the noise figure would be about 10 dBSPL (or dBA assuming that the -120 dB figure from Manley is A-weighted ?). This is far below what I experienced on a Reference Gold.
Actually Manley specifies an electric noise level at the input of the internal preamp in the mic (EIN means Equivalent Input Noise). We cannot derive the microphone self-noise from this figure without knowing the gain of this preamp. Let us assume that this gain would be equal to 20 dB. Then
x would be equal to -100 dB re. 1 V and the noise level would be equal to 30 dB SPL. This is certainly closer to the truth than 10 dBSPL.
I asked Manley about that. They did not answer.