At 8:47 AM -0500 6/23/06, Curt Olson wrote:
>the ORTF file was recorded with the cardioid AT-3031s.
Yes. I don't think omnis and ORTF even mix.
> I don't consider this to be a "boundary" rig, but rather a
>"barrier" rig. But because the mics lie so close to the barrier,
>there's definitely some boundary effect that comes into
>play.
Semantics, but maybe for clarity its important. The stereo image and
the tonal balance are affected by the proximity to the wood--
boundary effects. When I think of a "barrier," I think of a barrier
in a Jecklin like this one. http://www.core-sound.com/jecklin/1.php
with the mics away from the barrier. Your rig uses spacing on the
order of the spacing between the ears so it also has binaural
characteristics, (yet the barriers probably attenuate some "across
the head" timing differences) Then, your omnis are front facing--
more Jeckiln barrier like in this respect. I dunno, maybe "fron-
facing binaural?" but simply, "barrier" doesn't cover the most
important attributes for me.
>
>Incidentally, I've been surprised to discover from my tinkering that
>the barriers in a rig like this don't have to be very large to produce
>a nice image. I'd be especially interested in hearing any contrary
>opinions about that.
That is interesting isn't it. Though there may be some roll-off in
the lowest octaves if it was measured.
>If I had two phantom power supplies, I would have run the test with the
>3031 ORTF rig and the 3032 parallel barrier rig, also shown in the
>photo. That would have been a much better test, as both are a bit
>"huskier." But alas...
I think it can be wise to use the same two mics if comparing rigs is
the goal. Even four of the same model mics can have differences that
interfere.
>
>> I'm not sure the volume is matched close enough for extreme scrutiny,
>> but here are the sonograms I got from the fireworks flurry:
>>
>> https://pantherfile.uwm.edu/type/public/temporary/
>> FireworksTest_Sonograms.gif
>
>That's also an interesting point. Because of the tonal differences
>between the 3031s and the 183s, and also, I'm guessing, because the
>imaging is so very different, it was harder than I expected to get a
>decent level match across the whole sample.
You did a great job anticipating levels with the fireworks. Two rigs
may respond differently to loud sounds depending on sound's position,
so I'd probably try to match the background levels. By running two
decks, you've made that a lot easier to do because you can A/B the
same moment. The calibration issue reveals another reason to use the
same capsules. In your case, the AT3031's will probably produce more
signal at the frequencies associated with urban presence than the
183's. If you are comparing mic performance in the same rig, no
problem. But when you are comparing rigs, using different mics makes
harder to tell whether differences in amplitude are from the rigs or
mics.
>
>Thanks for your feedback, Rob!
>
>Curt Olson
>
>
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