Excellent work.....
Martyn
Martyn Stewart
Bird and Animal Sounds Digitally Recorded at:
http://www.naturesound.org
N47.65543 W121.98428
Redmond. Washington. USA
Make every Garden a wildlife Habitat!
425-898-0462
-----Original Message-----
From: Wild Sanctuary
Sent: Sunday, November 28, 2004 1:47 PM
To:
Subject: [Nature Recordists] MHK 800 prelim field test discussion
On the eve of 5 November, Rudy Trubitt, Bill Rainey, me and my wife,
Kat, ventured out to a bat observation site just north of Bolinas,
California (north of San Francisco along the coast about 1 hour's
drive) to test the Sennheiser MKH 800 (reputed to be acceptable for
signal to 50kHz). First, aside from the field test, Rudy did a test
in his facility and then we sent the report to the company for
feedback. Here's what we found:
Rudy's comments;
OK, I have a few hard numbers:
Test methodology:
An MKH-800 was connected to a Grace V3 mic-pre A/D with a gain of 55
dB. After a slate was made, the mic was placed into a foam-lined box
in a relatively quiet room to minimize the contribution from noise in
the surrounding acoustical environment. The left channel of Grace
preamp was terminated in a 200 ohm dummy load. V3's dither noise
turned OFF.
Sampling rate = 96 kHz, 24 bit data was recorded into Fostex FR-2. 24
bit 96 kHz stereo files were recorded an analyzed in Adobe audition's
Frequency Analysis window.
MKH 800 noise-floor appears to rise 10 dB per octave starting at about 10
kHz.
7 kHz -112
10 kHz -110
20 kHz -100
30 kHz -93
40 kHz -90
On the terminated channel, there is a very very mild rise in the
noise floor, but perhaps only about 1dB over three octaves.
In contrast, an MKH 20 had the same rising noise profile up to about
20 kHz, after which it began rolling off. A Schopes CM6 with MK4 card
capsule had a roughly flat noise floor from 10kHz up. Same flat
noise curve from a Neuman KM120 (figure-8)
Note that none of these tests actually measured the mic's frequency
response at ultrasonic frequencies. But the rising noise floor of the
MKH-800 matches my subjective analysis of our Bat recordings.
You mentioned putting some preliminary results on the
naturerecordists list? How about you do a write up and let me give it
a once over before posting.
It would be nice to get some feedback/confirmation from Sennheiser on
this before spreading it around. I'm pretty confident about the
results, but always nice to do a little fact-checking before
publication.
Rudy
****************************
Sennheiser's response;
Hello all,
I did relay the subject to Manfred Hibbing, the brain and designer at
our home office, who is THE MAN behind the current versions of all
Sennheiser RF-condenser microphones, and I am happy to share his
input to the reported observations:
The Grace pre-amp is ok and out of discussion. The MKH800 indeed
shows an increasing noise floor at high frequencies like all MKH
microphones due to a special design principle. The MKH capsules are
optimized for high electro-acoustical efficiency at frequencies where
the human ear is most sensitive to noise. Thus the audible (weighted)
noise performance is improved. However, this design is related with a
high-frequency roll-off of the capsules which is compensated for by
electrical equalization in the microphone circuit. This increases the
noise floor at very high frequencies where our ears are rather
insensitive as can be seen from the steep cut-off slope of the CCIR
weighting curve. While the frequency response of the MKH20 to MKH80
is limited to 20 kHz, the equalization of the MKH800 is continued,
and the noise above 20 kHz is increased as well. The resulting S/N is
still superior to microphones without electrical equalization
technique. For instance, a 1/4" measuring microphone with a
comparable bandwidth will contribute considerably more noise as the
S/N decreases with decreasing diaphragm diameter.
Uwe Sattler, Sennheiser USA
All the best, folks,
Bernie Krause
Wild Sanctuary, Inc.
P. O. Box 536
Glen Ellen, California 95442-0536
Tel: (707) 996-6677
Fax: (707) 996-0280
http://www.wildsanctuary.com
--
[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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