=C2=A0
A few weeks ago someone, I think it was David Brinicombe, mentioned observi=
ng HF
noise in Sennheiser MKH 20 microphones. I've noticed it too, when looking a=
t a
spectrogram of a quiet environment.
This morning we did a comparison of a 3032 next to an MKH 20 on the carpet =
of an
interior room, covered with some blankets. The diffuse-field HF boost switc=
h was
in the flat position. I used the preamps in a Sound Devices 744T. I posted =
an
expanded-scale picture of the resulting spectrum at:
http://www.dandugan.com/downloads/Nature_Sounds_Photos/AT3032_v._MKH_20_noi=
se_via_744T_preamps.png
Red is Sennheiser, green is Audio-Technica. The down-sloping curve on the l=
eft
is obviously ambient noise. I tried to match the levels at around 500 Hz. I=
believe that above 1K we are probably seeing mic self-noise plus preamp noi=
se.
The "hiss" from the MKH 20 is obvious. I put hiss in quotes because I can't=
hear
this noise at all. It isn't trivial however. I see that up-sloping top end =
in
recordings from quiet locations.
The tonal artifacts in the 3032's spectrum, especially in the range 400-1KH=
z are
curious. They could be from the mic or the preamp, not investigated yet.
My first guess is that the MKH 20 might be equalized in its electronics to=
compensate for a naturally rolling-off HF response of the capsule.
-Dan
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