Posted by: "Rob Danielson"
> At 7:41 PM -0400 8/31/06, Walter Knapp wrote:
>>> I tried a loaned pair briefly,
>>>modifying my MKH-20 SASS to hold them (made shim tubes). There's a photo
>>>of them in my mod SASS page in the SASS, and a couple comparison
>>>recordings to the MKH-20 are linked:
>>>http://frogrecordist.home.mindspring.com/docs/mod_sass.html#AT3032
> I did several ears-only run-throughs. The 3032's files are louder
> which itself is a surprise. After some volume balancing, I found the
> mics much, much closer in qualities than I would have ever guessed.
> The variation in the background content in the home location masked
> all of the distinctions I thought I had made. At Whitetail, both mics
> endure the Hi-Hz concentrations of the( cricket?) frogs quite
> similarly. Is there some 8Kish hiss in the right channel on the 20's
> that's not there in the 3032's? Thanks for making and sharing this
> extremely interesting comparison. I'm enjoying becoming familiar with
> 17' Tripod/SASS characteristics too. Rob D.
>
The photo and samples have been up since june, I've mentioned them a few
times.
Remember, these were recorded by my usual adjusting to the meter on the
recorder. And there is 20-30 min between the two samples at each place
as I change mics and shims in the one housing. The frog calling is not
as steady as it seems as to level. So, louder/quieter comparisons are
probably not meaningful. While the Portadisc was set with something like
15dB headroom, the actual headroom on the recordings ended up more like
a couple dB. This is due to the cricket frogs who's calls always fool
the meter due to their short transient nature.
Note that the center frequency of the cricket frogs is under 4kHz, which
I'd not really consider high frequency. They are a challenge for mics
and recorders to duplicate really well. And the mp3 encoder has it's own
problems with them.
The 8kHz ish thing I think you are finding is a harmonic of the cricket
frogs, I measure center of that at about 7.9kHz. It's present in all 4
tracks I recorded at Whitetail though I think the MKH-20 got it clearer.
The cricket frogs were all around the edge of the pond, but most
concentrated in a grassy corner that was about 60-75 degrees to the
right of center for the mics. So, they are louder from the right on average=
.
Also to the right side 75 yards or so is the drainage channel from the
pond (not much going out of the pond, however), and that side has large
trees not present in the other directions. There's also a simple
concrete slab boat launch off that way. There is a wood slab dock in the
middle of the left field that can sometimes be detected in echoes.
Also note there are man made sounds in the background at whitetail,
distant trucks and airplanes. They are very faint in the recordings.
That of course comes and goes, it's actually a long way from the roads,
though it's right on one of the approach patterns for Hartsfield
airport, about 40 miles out. One of the problems with highly sensitive
mics is that the distance you need to not have man made sounds
increases. Same holds true as you move to quieter and quieter ambiance
recording. For the SASS on the high tripod, 5 miles may be too close.
And I've had airliners interfere from more than 20 miles.
This sort of recording is not a big challenge for the self noise of the
mics, where I think you would find greater differences. The SASS housing
does a lot of shaping of the sound, including a approximate 4dB gain to
the mics. This farther buries the self noise and makes the sound more
similar. Diaphragm size of the mics is also similar. So, it should not
be too surprising that the two mics come out similar when mounted in the
SASS. More usage under more diverse conditions would bring out
differences. At least in a SASS the AT may be a acceptable substitute
for the MKH for a much lower cost. At least if primarily call recording
is contemplated, or louder ambiance sites.
The high tripod has become a pretty established part of my system. It's
not always practical to set up, but when it is I often use it,
particularly with the SASS. The simplification of the soundpaths
generally gives a clearer recording compared to doing it down at more
normal ground levels.
Walt
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