I can add a little something to this topic.
With a mixer or equivalent, and bringing the output back down to mic level, it is certainly possible to use 2 or more mics to train ToneDexter. You'll get a sound that picks up the instrument's sound from more than one perspective. Or you'll get two different mic flavors, which can also be useful if your single mic isn't giving you what you want.
However, there is a hidden pitfall with this approach: phase cancellation between the two mics. It is real and will definitely degrade the result. I usually counsel folks to get one good flat pencil mic, such as the Slate ML2, and try multiple positions until you find a few spots that sound really good with your instrument.
If you're DAW savvy and have an audio interface, you can also train from recorded tracks, as Doug has mentioned. This allows EQing beforehand to tailor the sound of the resultant WaveMap. There is another advantage: you can time align multiple mic positions recorded at the same time. Time aligning and then blending two or more mics will allow you to almost completely eliminate phase cancellation issues.
I've just done a series of recorded tracks with various guitars, using 4 mics into 4 separate tracks simultaneously.
The mics were:
- down under: SM81
- 14th fret Slate ML2
- out front Slate ML2
- up top: Dayton Audio EMM6 Omni measurement mic (approximately what player hears)
4 mic training side view.jpg
4 mic training rear view.jpg
4 mic training front view.jpg
After time aligning all the mic tracks, I trained WaveMaps on all single mic, 2-mic combinations, and also on a couple of 3-mic combinations. It all worked well and was informative:
- As expected, some guitars had preferred mic positions.
- Some positions sounded better than others.
- The combined results were lukewarm at best:
- None of the 2-mic combinations were as satisfying as the better single mic WaveMaps.
- Some 2-mic combinations sounded better than the worst single-mic position.
- The 3-mic combinations were all duds.
YMMV.