If he has good large condenser mikes, he should be able to move them back further than 1-2 feet and still get a good, full sound. I would think a lot could be gained by just moving the mikes around a bit to find the sound that you want.

My guess, though follows jeffp's idea--that the problem has more to do with the room, as boominess is associated with low frequency reflection-- if you're like me and have old carpets of one sort or another rolled up in the basement, they make useful no-cost wall covering/acoustic curtain.