tatiana irvine wrote:
> Hi Everyone,
>
> I just joined this list and I'm going to jump right in with a question. I am
> looking for advice about just how far to space omnis when recording stereo
> atmospheres in nature (as in 2 omnis on a stereo bar, not "binaural").
>
> What results has anyone out there gotten with different distances? I spoke
> to an engineer for National Geographic's "Radio Expeditions", and he
> recommended 14 inches- is this an arbitrary style thing, or is it necessary
> to space them that far apart to get enough seperation to make up for the
> lack of a human head between them?
>
> I have only used these omnis for recording music, which is a bit of a
> different bag due to such a strong primary sound source and associated phase
> concerns-
>
> Yes, I know....use my ears....just curious about approaches...
If you wish to try omni's without a barrier, then the rules are really
no different than in music. Except your soundstage may be hundreds of
yards wide, the "room" acoustics is entirely unpredictable and uneven,
and the performers do no retakes and perform from where they please, not
in standard arrangements.
Phase concerns are the same. Pretty much you should assume your
recording will not mix to mono well.
I expect the National Geographic engineer may have been thinking about
mic setups for a narrator or close mic of a individual calling bird.
Sounds way too close together to get much with a couple omni's as far as
the overall soundfield goes. I expect the "stereo" you will get from
that spacing will sound more mono than stereo. The National Geographic
engineer has to constantly be aware of how his sound will mix to mono,
so probably compromises.
Most of the nature shows I've seen when they had a mic in the picture it
was on a fairly short boom, and was a standard zeppelin with windjammer,
so the mic was hidden. But, about all that fits in that for stereo would
be a MS setup. I expect in a lot of it what's inside is a MKH-416
shotgun mic or the equivalent, ie mono.
My guess is that if you are trying to record a soundfield, that you can
forget the bar unless it's a long one. 2 meters or more may be where you
end up. And you may find that a high placement will work best, 15' or
more up, to avoid the local ground reflections. You really will have to
just try and listen. There are no rules that work universally. Nature
recordists are really, for the most part, just getting into stereo, many
still record with single mono mics. So we don't have hard and fast rules
worked out like music has.
One other technique to consider that I know some music pros use. Do
Pseudo Stereo. The description of how one of those folks sets up is
interesting. He sticks a finger in one ear and wanders around listening
for a "sweet spot" for the other ear. He places a mic there, then sticks
his finger in the other ear and repeats the process. It's Pseudo Stereo
in that you are not trying to accurately portray the soundfield, but are
trying for a listenable soundfield. Obviously this route could be
extended to many more mics and then mixed to sound good. And depends
very highly on the listening abilities of the person setting it up.
My own suggestion of a good thing to do with a pair of omnis for nature
recording is to go with a barrier and reduce the spacing to head width.
This also improves the portability of the setup, a real consideration in
nature recording.
The SASS enclosure, fitted with good omni's does a excellent job. It's
part head spaced omni, and part boundary mic. It has some binaural
characteristics, but works well with speakers too. If you have the
omni's then the parts from crown to do it don't cost a lot. Some
machining is required to mount the mics. Here's what a couple of them I
made look like:
http://frogrecordist.home.mindspring.com/docs/sass_mkh110.html
http://frogrecordist.home.mindspring.com/docs/sass_mkh-20.html
And here's what I've gotten in my first tries, the subjects are frogs:
http://loscan.home.mindspring.com/B.SASS.MKH110.mp3
http://loscan.home.mindspring.com/B.SASS.MKH20.mp3
http://loscan.home.mindspring.com/S.SASS.MKH110.mp3
http://loscan.home.mindspring.com/S.SASS.MKH20.mp3
http://loscan.home.mindspring.com/SP.SASS.MKH110.mp3
http://loscan.home.mindspring.com/SP.SASS.MKH20.mp3
Another spaced system to try is the Jecklin Disk. Here the omni mics are
spaced head width, 165mm, with a solid disk of 280mm diameter between
them that's covered with sound absorbing material. Anyway, that's the
original dimensions.
I've also seen some homemade versions of the Schoeps sphere. Usually
made from a toy ball of suitable dimensions. I've not heard of any
nature recordist trying this one. The foam block system Rich Peet has
would be somewhat similar. When you get into this stuff the analysis of
the soundfield pickup from the mics is complex. Usually just listen, it
works or does not, don't get into why too much.
Walt
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