Microphone positioning is one of the core parts of sound engineering. If you get this bit correct, mixing becomes easy.
One thing that can happen too quickly, however, is that one can start looking for the ‘correct’ mic position in books, on forums or interviews with famous engineers. The trouble is, there isn’t a ‘correct’ position. There’s hardly even a good starting point!
Mic positioning can be absolutely anything. It helps to imagine a huge bubble around whatever you’re recording and remember, anywhere in that bubble might be the correct place to put the mic.
How do you know where to place it? What should you be listening out for?
There are two major thing I always try to solve with mic technique.
The first is probably the most important. Space!
When recording a new sound, it shouldn’t get in the way of any other part, or start to sound mismatched. Keep moving the mic until you listen and it seems to have found its space. Don’t worry if the sound is different tonally to what you expected, it’s all about how it sounds in the mix!
The second is removing irritating sounds like fret board squeaks. Now, on something like an electric guitar, you should always try to remove this at the amp/guitar stage. Lower that treble for example! But with something like an acoustic, it doesn’t really have any way of solving problems like that (perhaps changing strings?) so use mic positioning to make those fret board squeaks sound balanced (you can’t ever remove them, if they’re there, but you can make them bearable, even pleasant, to listen to).
I was recently recording electric guitar and no matter where I placed the mic I couldn’t get a sound that wasn’t getting in the way of the bass and muddying up the low end - until I moved the mic out about 4 feet. Suddenly the guitar part sat perfectly against all the other parts in the mix. It wasn’t the tone I had imagined, but because it sat in the mix so well, it became better than what I’d initially wanted to capture.
Even when you’ve found some of your preferred mic positions for your room or music style, always experiment. You’ll be amazed at how the ‘correct’ mic position changes from song to song!