Rob Danielson, you wrote,
>When I look at the spectral displays of field recordings made with a
>range of different mics, they all reveal that a very, very high
>percentage of the total sonic energy in our environments is below 300
>Hz-- even in remote areas in the middle of the night. Very low
>frequencies are powerful and travel great distance and our powerful
>machines generate tons of it. I can roll-off everything above 1000Hz
>in a field recording and still retain 90% of the amplitude. If I use
>shelf filtering to "roll-off" below 150Hz, I'll be left with 10-25%
>of the sound recorded. Its traditional to "roll off."
In dialogue or species recording, yes, but not necessarily in ambient
recording unless it's a matter of survival.
>The harmonics
>produced by these Hz's are lost and the ability to define the mid
>range is adversely affected. Of course, the intrigue of recording,
>"space" has only been considered possible for about 15-20 years.
>
>In short, "I never met a low Hz I didn't like" -- that I couldn't
>find something useful in or about. Very, very few people have
>subwoofers that can reproduce this energy with smooth response, but
>I'm not sure that recordists need to attenuate this energy in the
>field unless its really dominate and one is interested only in the
>high register info.
I agree, it's better to record full-range and roll off later in post
production. One of the wonderful things about digital recording is
that unless it overloads, low frequency noise (like wind rumble in
the mic) can be filtered out very cleanly later. That wasn't true
with analog tape due to the intermodulation of the medium.
>I feel there are bound to to be gains in low Hz
>tech. Perhaps mic systems that use multiple capsules similar to
>bi-amplified speaker systems. But today, the topic of low Hz
>representation is still largely a practice of "Bass Management."
>
>>I'll continue beyond the scope of your question. The reason for the
> >boundaries is that in my experience, spaced omnis can give terrific
>>stereo imaging in an enclosed space with a specific targeted sound
>>source, such as a choir or orchestra. But for outdoor ambience, phase
>>interaction between the mics makes imaging a mess and destroys mono
>>compatibility every time.
>i
>If it helps to make this a lower priority, you can use an M-S
>processing based Stereo Image plug like Waves S-1 in post to achieve
>mono compatibility when needed.
M-S processing doesn't work on spaced mics--it's only for coincident arrays=
.
-Dan Dugan
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