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Re: MKH20/AT3032 comparisons (was Shure VP88 vs Sennheiser MKE44

Subject: Re: MKH20/AT3032 comparisons (was Shure VP88 vs Sennheiser MKE44
From: "Walter Knapp" waltknapp
Date: Sat Sep 2, 2006 10:56 am (PDT)
Posted by: "Rob Danielson"

> The cricket frog calls are similar to "jingling keys"--  a sound
> often used for testing sibilance and high frequency transient
> response.  As one of the more telling tests of high end performance,
> its impressive to see the 3032's hold their own.

That may be the impression from listening, but the calls are quite
different from the precussive harmonics from bits of metal. They are
made with vocal cords vibrating in air. I've not made a study of cricket
frog calls, but roughly the basic components are small bursts of a set
frequency about 1-2 thousandths of a second in duration. No after
vibration as you would have with the metal.

As a biologist and having the advantage of hearing the actual calls with
my own ears, the MKH-20 rendition is a little more true to life than the
3032's. The 3032's render the calls a little too grainy. Still not bad
and easily recognizable.

We have two species of cricket frogs here, and it can be tricky to tell
them apart at times. So I'm used to dissecting the calls to determine
the species.

> Interesting theory. Perhaps the reflected and direct waves being in
> phase provides a similar  advantage to both mics and lessens
> differences.

I actually think the 3032 is probably at a slight disadvantage on the
reflected and direct wave part of a boundary mic due to it's hard,
slotted diaphragm cover vs the screen cover of the MKH-20. I don't think
the acoustic coupling of the 3032 to the surrounding boundary is quite
as good. The diaphragm of the 3032 is aligned to the ends of the slots
but slightly lower so the coupling has to be over this slight lip
through slots. The MKH-20 diaphragm is more exposed and even with the
top of the housing so aligns better through it's fairly open screen.

Note that the boundary of the SASS considerably modifies the polar
patterns of the mics. From the all around omni to more or less a
hemisphere. This is going to modify the frequency response curves of
each mic some.

> Your comparisons are likely to encourage more experimentation with
> 3032's, but probably not with the advantages of the mkh-20 reference.
> Eric measured 8dB(A) self noise on the 3032's so there's a decent
> chance the similarities could persist in quiet locations.

As I noted I did not have the opportunity to try the mics in a really
quiet site so cannot really do more than speculate. I would have loved
to have them set up for comparison on the Florida site at 3 AM. That was
a quiet site.

I'm willing to believe the mics are lower self noise than the 16dBA spec
from the two examples I tried. But for every example to be 8dBA I think
will turn out to be a big stretch. The two I had did not sound that
quiet by ear. Maybe as quiet as a 30 or 40, but I won't swear to that even.

I do think they are worth more experiment for nature recording. Even if
the self noise was 16dBA that's a lot lower than mics folks keep talking
about. And they do have pretty good sound.

>   Your rig's ability to get completely above the trees in some
> instances is ingenious. Thanks also for the breakdown on the SASS
> construction on your website!  Rob D.

I would not say it get's above the trees too often. But the brush is
generally lower and so are lots of ground reflecting/absorbing surfaces.
 From measurements I made many years ago ground clutter modifies sound
levels considerably up to 6 or more feet in natural (forest)
surroundings. We were doing a highway traffic noise study along the
North Cascades Highway in Washington State, a preliminary to a new
campground which was in forest off the highway. We normally measured
with the meter at 5' and needed to know the falloff to calibrate our
noise model. As part of that we did measurements in the forest from
actual ground level up to 10'. The height data was never written up and
published and I don't have it anymore.

Note like so much of what I do this is not a original idea with me. Klas
was the first I remember in the group who talked about using a high mic.
Though he was talking about using a high parabolic pointed downward to
minimize unwanted noise behind a wanted caller. The greater clarity
became obvious when I started trying it.

Walt





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