Take a look at my live room, please

first of all, hello. this is my first post here. i've been browsing this site for a while now, and have gained a lot of info. Pictured below ( i hope i got it to work) is my live room with dimensions. i won't go into much detail about why it is the shape it is, but it's was pretty much the best use of space for what i was working with. The room has already been built. the walls and 12 ft ceiling are all sheet rock. i built this room to be a big sounding room for recording naturally big drums. it certainly worked, maybe a little too much! cavernous is probably the closest word to what it sounds like right now. but i have noticed some weird resonances, mostly around the corners. my question is this: how can i tame the weirdness and still keep it fairly live sounding? i have ideas, based on what i have learned here. corner traps, panel absorbers, and probably some diffusion on the ceiling since it runs parallel to the floor. but i am on a budget (aren't we all) and would like to start off keeping it under $500 for the treatment. everyone's input would be very helpfull. i don't want to spend money on traps if that's not where the problem is. anything you guys can tell me just by looking at the dimensions? thanks! chris

Maybe something like this - very rough, but should kill flutter and some modal stuff without killing the sizzle too much... Steve

thanks for the tips!

poly plan. if you need a middle brace for rigidity, keep it offset from center to keep resonance response different for each "half".