I want to preface this by saying that I've been practicing metal vocals for about 5-6 years now. I spend most of my time practicing during commutes to work and during other travel times, and in that environment I actually feel like I have a fairly powerful voice, however the issue strikes when I take things to my studio. For whatever reason, when I am in my studio recording vocals, things go to complete shit. Listening back on my vocals, they sound really flat, and not very full at all; the best way I can describe it is it sounds like there's a lot of misplaced air flow, you can tell that I'm growling/screaming but it sounds weak and honestly pretty damn embarrassing. My vocals sound decent in the mix, it seems to cut out the flat edges a bit, but I really don't like the idea of only sounding good in mix. This happens with clean singing as well. I'm trying to figure out if it's maybe just my studio set up, can this occur due to poor sound proofing? Is it possible that my mic/pre-amp could be causing this? (I use an AKG C21 condenser mic and Shure x2u pre-amp) I'm only questioning the gear because, as I've said, I can actually tell that my voice is very full and strong in other environments.

tl;dr: My voice sounds great while driving, but sounds like trash in the studio. Could gear/sound proofing cause that discrepancy?
Well it could be. If it still sounds and feels the same to you as it does in the car and such. If it doesnt feel and sound the same, theres ways to bring it back. I have experienced the same thing. I would suggest slamming a couple beers right before recording. It might sound silly but give it a try. Or do some cardio exercise before which will expand your vocal chords and lungs. Also when your sitting down you might be breathing slightly differently then when your standing up doing vocals. Try the beer lol good luck with it
I've tried the liquid courage thing, I'll occasionally drop by my studio after drinking a bit just because I seem to feel like I will sound better, but I don't think it's ever made a serious difference. I've considered that it's possibly a breathing thing, but I've tried recording while sitting down, or kneeling to increase abdomen pressure and it doesn't make much of a difference. I'm curious to know- does anyone else have an issue with their vocals sounding weak in poorly insulated rooms? I honestly think it must be my technique because I feel like you can still tell that someone has a good voice regardless of the room quality.