I asked the questions because I am evaluating a new Ultra Sensitive ECM. Its a
electret capsule not yet avail in the US. Since the naturerecordists group uses
self-noise so often to compare mics I wanted to know what the noise output of
this new capsule might be. The mfr does not include noise output in its spec.
These are the guys that make the EM23 cartridge.
http://www.primocorp.co.jp/product/PDF/EM158.pdf
The mfr characterized 5 samples for me and I'm currently trying to build a mic
around them. They may not be suitable for many DIYers because they are very
delicate physically. For instance the housing is much thinner than paper and
the characteristics can easily change with the introduction of high heat from a
soldering iron.
The sensitivity of the 5 samples ranged from -28 to -31 dB
Thanks guys for all the help. I'll study the rane.com references and maybe
someday I won't be such a newbie.
The 1st one I assembled seemed to perform as good or better than my 183's. I
have a pair of 183's I use as quasi-binural and another pair in a parabolic. I
use a NH900 and a RH10 for my recorders.
I feel it may be appropriate to move any further discussion to the micbuilders
group.
Thanks,
Gene
Rob Danielson <> wrote:
At 4:22 PM -0700 9/20/05, Dan Dugan wrote:
>Eugene E Dorcas wrote:
>
>>Can you calculate the output noise from other specs such as
>>signal-to-noise ration and sensitivity??
>>
>>For instance: If the sensitivity is -32dB and the SNR is 75 dB,
>>what would the output noise be??
>
>Mic signal-to-noise is measured from 1 Pascal, which is 94dB SPL.
>
>If the SNR is 75dB, you can calculate the self noise of the mic:
>94-75 = 19dB SPL (probably the SNR was spec'd in dBA, if so it would
>be 19 dBA).
>
>The sensitivity is more relevant to the question of whether that mic
>would get its own noise above a particular preamp's input noise
>level, called Equivalent Input Noise (EIN). If it does by more than a
>few dB, then you can get the best performance from the mic.
>
>http://www.rane.com/note145.html
>
>The noise output of a mic with 75dB S/N and -32dB sensitivity (very
>hot!) would be -(75+32) = -107dBV. dBV because the sensitivity is
>measured re 1 Volt (1Pa/1V).
>
>0dBu is 2.2dB below 1V (don't ask), so the noise output voltage of
>the mic in Haleakala crater would be -104.8dBu.
Professor Dugan, I signed up for the course in Audio Measurement
Reference Levels, again. Charts 3 and 4 here
http://www.rane.com/note148.html show mic sensitivity as -dBu and as
mV/Pa. Seems not to be a simple arithmetic relation/conversion. What
is the "-32 dB" sensitivity measurement you are working with
referenced to or need it be? Rob D.
>That would be way
>above the noise of even a commonplace preamp (like EIN = -125dBu). A
>mic with 10dB lower output than yours, like the Shure WL183, is still
>hot enough to make the noise of a cheap preamp irrelevant.
>
>Another confounding factor would be that preamp EINs used to be
>measured in dBm, and some still use that measure. Let's not go there,
>either. Any real audio engineers here, please check my figures.
>
>-Dan Dugan
>(I'm not an engineer, but I play one at work.)
>
>
[Non-text portions of this message have been removed]
"Microphones are not ears,
Loudspeakers are not birds,
A listening room is not nature."
Klas Strandberg
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