sixways said:
Regardless, does it sound like EQ is my problem? I can't see compression fixing the issue...
It's hard for any of us to tell anything without hearing it, but it sounds like the tracking setup may be thr root of the problem. I'd try re-recording well before I started throwing a bunch of hardware and software at it.
First off, the room sounds like a big problem. Recording vocals in what is basically a dead closet is taking away natural reverb and high end at the same time, while probably playing havoc with the bass, squeezing out all sorts of bass modes. This could well explain what you're seeing on the RTA.
If you can get the artist to re-record, have him come out of the closet (literally, not psychologically

). If you want a similar sound as the guitar, record in the same location that the guitar was located. Put some absorbtive backing behind the vocalist if you want to deaden the rear reflections the same way the guitar is deadened by the player's body. If you want a livelier sound, try moving the vocalist to the kitchen, bathroom or large stairwell to get some natural bright room reverb.
Also, you might want to try changing up vocal mics if you have a choice. Matching mics to vocalists is a black art; what works best on vocalist A doesn't necessarily work best on vocalist B.
OTOH, if re-tracking is simply not an option (e.g. the singer has died, or even worse, moved to New York City

), then you have to choose the lesser evil of trying to fix the tracking you have.
My first question is if he's heavy at 100Hz (skip the RTA, does he *sound* heavy at 100Hz?), why haven't you cut there?
But instead of that, I'd do the ol' parametric sweep first, sweep through the frequencines on the vocal track with a narrow-Q, high-boost band of parametric EQ and look for the frequency or frequencies where the "boxiness" really jumps out at you. When you have those frequencies figured out and isolated, pull back on the gain until you are cutting them by a few dB instead of boosting them.
Do the same thing with the guitar. sweeing the guitar track(s) to look for honking freqs there as well. They hopefully and probably won't be that similar to the bad vocal ones.
Then once you have those offending freqs notched out, pull back on the overall level of the vocals by just a couple of dB and add some ambience to the track in the form of a "warm room" or "medium plate" reverb. Don't make the tail too long, and don't make the vocal so wet with reverb that the casual listener will notice it's there. Just enough to make it sound natural with a bit of the edges rounded off.
Then try mixing the two together, adding a little of the same kind of verb to the gits if you have to to match the sound.
HTH,
G.