I can't help with specifics of what to do after(I'd just "play" with it - EQ, etc.), though with this guy I might try to do something WHILE recording, too? Can you try a different mic? Maybe another condenser or a dynamic - maybe it's still proximity effect? Or, maybe have him speak "off" the mic a bit(Mic higher/lower/left/right of him?).

The deadest studio I work in STILL "sounds" sometimes, with some people, some mics, some styles, etc. and this "sound" is sometimes hard to work with.

Just some thoughts...

TG

If he has a big voice, then you might try a big room and roll off the lows. Don't be afraid to experiment. I have a classically trained voice and I have yet to like the sound of any vocal booth I've recorded in. Keep the placement that is giving you the highs and clarity you like.

Phil

Vocal Guide lines

to add fullness, try adding a few dBs at 150 Hz
to get rid of muddiness, cut a few dBs at 200 to 250 Hz
to add clarity, boost a little at 3 kHz
for more presence, add at 5kHz
to add air or to brighten, boost at 10 kHz
to get rid of sibilance, cut a little between 7.5 to 10 kHz

Have you tried an omni? (no proximity effect) How 'bout getting farther from the mic. I find some folks don't sound good until they're about 2' from the mic.

Ditto on the omni recommendation in a "dead" booth. Does your mic and/or pre have a bass roll-off/hi-pass filter? If so, try using them in combination with mic choice and placement.

boomy

If the booth is small and he's huge, it may be that the remaining air mass in the booth has a resonant frequency in the 80 to 120 hz range. I'd get him out of the booth. If you have no choice, there's eq. Don't use a rolloff - just find the resonant point and dump it with the right q.

On creative solutions, you might try common mode rejection. Take another mic - hopefully identical, put it in the booth with him, place it pointing at the other mic next to his head but behind his mouth, and put the two mics out of phase. The boomyness might phase cancel. experiment with placement to cancel the right frequencies. This can actually be a very good type of solution.

How does he sound live with no electronics?

My guess is he sounds great.

First I would change mics and see if u can get a better result.

If that does not work I would have him back off the mic.... It's easier to eq later then add filters and all kinds of stuff to make it right....
Maybe a less directional mic placed further away would improve things.... Dunno!