> I just wondered if members would be willing to share more info on
> their microphones commonly used in the field.
With trainees, I used the idea of "fetch" - similar to "reach" but
more definable. It is basically the image distance judged by your ears
alone, compared to a single cardioid.
("Reach" is a different concept more related to the maximum useable
distance.)
Imagine a bird singing in a tree in the garden or on the roof. With a
quiet background, a single cardioid will get you a good recording at
10 yards (metres for those in the 21st century) if the bird doesn't
fly away. An omni would need to be about 5 yards for a comparable
recording, so has a fetch of 1/2, but the bird has gone by now.
Short gunmics are the workhorse of most outdoor recording and score a
fetch of about 3, so the bird on the roof would still sound good at 30
yards.
Long gunmics have a fetch of at least 5 and will bring in stuff you
couldn't get otherwise, like shy wildlife. They need to be aimed
accurately and are expensive, and heavy when mounted in a good blimp.
These mics are much less directional at low frequencies so a gentle
bass roll-off is often needed.
Parabolas are very different. They have a fetch of more than 5 at bird
frequencies but are even more frequency dependant than long gunmics.
They have to be accurately aimed at a source for best results. They do
have a very useful advantage as they focus the sound, producing an
acoustic gain which often swamps any mic noise.
(Plug for the Brinibox rig which has a gain of about 12dB and can use
crap mics.)
http://www.stowford.org/sounds/brinibox.htm
Cost is important of course, but what you really pay for between
affordable and pro mics is a low noise level. Frequency response is
good in most mics nowadays on-axis, but off-axis even the most
expensive gunmics are all over the place.
Stereo is a whole new ball game and adding a second mic will reduce
the fetch by about half. In real life background noise is less
apparent to the ears as our brains can select what to listen for, and
this is also true to some extent with a stereo recording.
Almost all stereo rigs are equivalent to a pair of cardioids with a
low fetch, but often with a good stereo image. Nice sound but you have
to get closer. I use crossed gunmics which is a clumsy rig but it
retains a good fetch. Here's a woodpecker at 60 metres:
http://www.stowford.org/recordings.htm#woodpeckerbeech
A problem arises when adding a sideways fig-8 to a gunmic to make an
M-S pair. When this is decoded to L-R stereo, the pickup is near omni,
almost back to a fetch of 1/2. The good news is that the gunnmic fetch
of 3, say, is still available in mono. These "zoom" mics are often
used on video cameras, but the S signal is picking up very little that
is in the picture.
David
David Brinicombe
North Devon, UK
Cogito cogito ergo cogito sum - Ambrose Bierce
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