At 11:29 PM +0100 2/16/05, Klas Strandberg wrote:
>Rob, Pres etc - wer'e back to the same questions again:
>
>How high output must a microphone give to
>override a certain mic. preamp noise?
>Or vice versa:
>How noisy can a mic preamp be, (Mini-Me preamp??) as the mic's output is s=
o
>high that all you hear is mic noise anyway??
>I don't see any good user-friendly approach to describe this.
The question rises from recordists who want to
record ambience or the acoustic setting along
with calls etc. I'll try again:
"I like to record ambience. Will a high
sensitivity mic be able to perform better with an
MD recorder in quiet settings?"
To test this, I produced a "quiet setting"
indoors with two clocks (one left and one right)
ticking in a room. The Sony NH900 MD recorder has
its record level set at "23"-- typical with
medium to low sensitivity mics outdoors. Three,
popular power-in -plug mics were compared:
R=F8de NT4 16 dB(A) 12 mV/Pa
Shure WL-183 22.5 dB(A) 40 mV/Pa
Panasonic WM61a 32 dB(A) 18mV/Pa
http://www.uwm.edu/~type/Mic%20Preamps/WR-183_WM-61A_NT-4%5e.mov
~8mb
(Please note, the Shure mics are model "WL-183" not WR." Sorry)
Adjust playback to a comfortable level on your system.
To my ears, the recording produced by the NT-4
(which was boosted 18dB to match the gain of the
183's) has more noise and less transparency than
the recording made with the Shure 183's. This
suggests to me that the effective self noise of
the MD mic pre at "23," is greater than 16dB(A).
If the effective self noise was lower than that
of the NT-4's, the recording made by the NT-4
would not contain additional noise and the 183's
would exhibit more noise. The MD pre mic is
contributing significant noise at a level of
"23."
Here's the easiest way I can phrase the advantage
of high sensitivity in a mic: In quiet settings,
a mic with high sensitivity allows one to lower
the MD's record gain and effectively lower noise
contributed by the MD's mic preamp. and produce
recordings with less noise.
Note that high sensitivity "numbers" are not
enough to go on. In this test, the volume output
from the Panasonic and Shure mics is
approximately the same, but their sensitivity
ratings are significantly different.
People who primarily record loud sources like
bird and frog calls will notice less improvement
in noise because record levels are usually lower
for these sources. Rob D
=3D =3D =3D =3D
At what ambient sound level does the advantage of
a high sensitivity mic diminish (with MD)? A test
comparing popular power-in-plug mics with louder
sources like bird calls with MD record levels of
"20," "16," "12" would be interesting.
>
>In my limited experience of all MD's etc, they seem to be good enough for
>any high output / low impedance output like the Telinga's...?
>
>Klas.
>
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