stancourtney <> wrote:
> ...I am not sure what frequency response I need.
While I'm not at all sure about Sasquatch recording, your recording problem=
is
similar to many in that you don't know exactly what you need, because you
haven't done it before. Given that you describe having heard/felt the soun=
ds
that you are interested in recording, I suppose that we would call that nea=
r
infrasound in the terminology of the web pages at:
http://www.esrl.noaa.gov/psd/programs/infrasound/infrasonic.html
I had originally assumed that you want to record sounds for later analysis =
but
not I'm guessing that you also would like to listen to the sound. That bri=
ngs
up the problem of reproducing the recorded LF sounds, but that's another pr=
oblem
for another forum.
I have had some experiences with the Sound Devices MM-1 in which it had
insufficient bass response. Unfortunately I no longer have access to any o=
f
that data so I can't say anything specific, other than that other preamps m=
ay
give better performance in this application.
In contrast to another reply, I would say that the choice of microphone sho=
uld
be the first thing to check, and not the recorder; if the low frequency sou=
nds
don't make it through the microphone then it doesn't matter what the record=
er
does.
I do a lot of measurements of recording equipment. Looking over the few
omnidirectional microphones in my collection, my Audio Technica AT3032 is d=
own
only a few tenths of a dB at 10 Hz, a microflown p-u 'match' probe rolls of=
f
below 100 Hz, a Schoeps Mk2 rolls off at about 23 Hz, Earthworks M30 is dow=
n
just 0.2 dB at 10 Hz, Shure MX183s roll off at about 40 Hz (I'm sure that's=
the
adapter), a microphone based on the Knowles FG capsule is down 4 dB at 10 H=
z, a
studio projects C4 capsule on a Rode NT5 body was down 0 at 10 Hz (but not=
nearly as good as that on the C4 body).
It seems likely that the Rode NT5 with their new omni capsule would be a go=
od,
low-cost microphone for low-frequency recording.
Your qyery has caued me to expand the range over which I usually test frequ=
ency
response. I usually go down to 10 Hz but I can extend those measurements d=
own
to 1 Hz or so. I have just one portable recorder at present and that's th=
e
Zoom H2, because it records 4 channels. If you use the microphone inputs i=
t
starts to roll off at 40 Hz and it's about 32 dB down at 1 Hz. Going in th=
rough
the line inputs it's 3 dB down at 7 Hz and 22 dB down at 1 Hz.
I want to point out that, just because the recorder or the microphone rolls=
off
a bit doesn't mean that you can't make a usable recording. It's quite
reasonable to equalize out the frequency response roll-offs for either the=
purposes of listening or analysis of the files. If I wanted to make a reco=
rding
that goes down to 10 Hz, I'd just use what I've got. If I wanted to go dow=
n to
1 Hz I'd have to do some modification of my existing equipment. Precisely =
what
I would do would depend on whether I could take a laptop into the recording=
situation.
If you would like to see any of these measurements let me know and I'll pub=
lish
some graphs to our web site.
Eric
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