This might not be helpful to anyone who reads this but me.
Recorded guitar today. Guild S-300D into an Orange Tiny Terror into a 1×12″ ported cab (similar to TL806).
I used a Coles 4038 going straight into my little sound interface’s preamp (Avid one track thing).
I aimed it pretty much at the center of the speaker, and at a foot away it picked up too much of my picking and sounded a little thin (I wasn’t playing loud). At about 8″ away it was a little too boomy. Will try 10″ away next time.
UPDATE January 8th, 2015:
Same setup again (all of it). I kept the microphone 10″ away from the amp and I got the same sound. At 10″ away there’s already a lot of bass because of the proximity effect. It’s not a bad sound, might even be a good sound, but it doesn’t sound exactly like what I’m hearing in the room. I should mention, though, that I play quiet enough that I can hear the acoustic sound of the guitar along with the amp. That could contribute to why it doesn’t sound the same. Anyway, I moved the microphone maybe an inch or two away from the center (off-axis) and things cleared out a little more. Not as boomy anymore. That’s something to keep in mind.