Ok... Lots of questions in there...
Do you go to great length to try to
position whatever you are recording
for best acoustics and mic position?
Yes - I go to great length to get the best possible sound from the raw recording. Yes, you can fix things in post, but these "Fixes" should only be used if something is "broken" about the recording. Playing with the mic position to get the best recording can save you a ton of time in post, and yield a much better, much more natural sounding recording.
Let's say you're recording an
elephant. He's in a pen and at one end
of it there's a big barn. Would you
try to get the elephant near the barn
to get some early refs and "liveness"
to the sound or would you try to bring
him more out in the open?
It all depends. Where does it sound best? Where are you getting the least amount of background noise? Does the Elephant settle down near the barn but get more energetic away from the barn? It's all about experimenting to figure out what sounds best.
What mic position techniques do you
have to record specific things? Or is
it always dead-on? Do you go off-axis
for recording a chainsaw for instance?
How about a lion roar?
Never recorded a lion, so I'll leave that one for Chuck.
As for position, you generally want to record with the mic on-axis. Basically, you want to keep the sound within the polar pattern of the microphone. There are a few exceptions, but they can only be done in VERY quiet environments (e.g. vocal booth, foley room, etc...). I wouldn't go off-axis for a chain saw, I would just use a high SPL level mic. If it sounds too "tinny" or "metallic", try a different mic.
For very loud SPL stuff do you walk
closer/farther until it sounds good in
How loud are we talking? Generally, I'll start with my mic at a safe distance and audition the sound, checking my levels, then adjust from there. I generally get the mic as close as possible without distorting the pre's. In-line pads are your friend for this. But make sure you know what your mic can handle first!
Also, for most sounds I have multiple mics at multiple perspectives, so if I'm using a mic close up on a loud sound, I'll also have a mic (or a few) back a bit to capture ambience, different sound characteristics, etc...
Do you use noise-cancelling headphones
NEVER!!!! Noise-canceling headphones have some of the worst frequency responses on the face of the planet! You'll never actually get an accurate representation of what your sound actually sounds like, then you'll get back home and wonder why your recording sounds so strange over speakers but great in headphones. I'd stick to the standards - the Sony MDR7506, MDR7509, or one of the Beyerdynamic ones (DT770, DT880).
Bose Quiet Comfort http://graphs.headphone.com/graphCompare.php?graphType=0&graphID%5B%5D=1743
Music recording is my main background
and I want to know if my knowledge of
acoustics can help apply to field
Very much so! My original background is music recording as well. Let me know if there's any other way I can help you!