For recording one of
the large acoustic bass guitars now popular, try a large diaphragm condensor
microphone.
Keep the microphone within a foot of the instrument to avoid reflections
from the floor. Place it about a half foot above the bridge; experiment
with how much you aim it toward the sound hole, but don’t go overboard.
Too much aim at the sound hole will add reverb, and you can always add
more reverb in the mix.