Okay, I know this is a commonly asked question but there aren't many concrete answers on the matter.
I'm going a little more in depth than just asking what the mics do.
Now, I'm soon ordering a Sennheiser MD421, already own an Sm57. I am a massive fan of miking guitar amps. The tone of a tube amp destroys the tone of any modulation program. I own a Krank Revolution 100w head and an Avatar 2x12 Contemporary Cabinet and the tone with a bit of EQ has given me really satisfying results being recorded with just the single Sm57.
The technique I've use is placing the mic toward the middle of the cone but angled toward the outer (I'll add a picture.)
Now this question is more based so I don't have to waste too much time mucking around with mic placement, but those who have dual mic'd (preferably 57 & 421), in your opinions, is it better to aim both mics in the same direction, capture both lows to highs with both mics, place one on the dust cap and one on the outer of the cone? etc...
Just trying to find what has worked well for you and what advice can be shared?
I play mostly metal in Drop C with overdrive and an ISP decimator so I like my lows but I love my mid range too, along with being able to blend it nicely into a mix.
-Sorry for such a long and confusing post, just ask me to specify anything if you don't understand :x
The important thing is to check how the phasing works together.
A trick that is sometimes use is to:
- find a position that you like for one mic
- turn the amp up full with no guitar plugged in, this will make it hiss quite loudly.
- route both miss to headphones, but put one out of phase.
-wear the headphones as you move the send mic around, and try to find a spot where the hiss cancels the most.
This will give a point that is relatively in phase.
It can be nice (but is not necessary) to try to get a different part of the sound with each mic. (brighter in the centre). You may have to use your ear more in this case.
Also, a Little Labs IBP can be very useful in dual micing guitar amps. There is also a UAD plugin version, and other plugins that probably do something similar (that I don't know)