Hi, You can make this room work but you will need
way more treatments if you want to do it without subs and eq.
As you already know, Eq can only be used on peaks and not on dips. If you only listen to the stereo, I suggest you use an absorber panel between the speakers (you already have sidewalls and ceiling covered
). Essentially, you need to create
RFZ which means absorption to the side, front, ceiling, and back. Also, extend the traps from floor to ceiling. Bass pressure is the highest at the bottom and top of corners. Porous traps will not be efficient below 80Hz and I would suggest you try using the MLV on the back of the traps. Measure the room and maybe build some membrane absorbers. With all those traps that you need, the ones that are not used for RFZ, you can add a plastic sheet to reflect the high/mid-frequency back in the room so you don't end up with "dead" space. Or, you could add some wooden slots. Speakers should be moved 1/3rd (1 meter) or 1/4 from the front wall and you should be sitting 1/3 or 1/4 from the back wall. Unfortunately, if you are really serious about sound quality, you shouldn't have anything between you and the speakers. Even if you implement what I suggested, you will still have some issues in the lower frequency range but it will sound much better than now. I've attached the picture of my room so you have some idea what I'm talking about. PM me if you need any additional advice. Btw, all my side panels are 4 inches thick with one-inch space between them and the wall. Bass traps have 6-inch insulation in a 7-inch frame with the MLV on the back. My TV is hidden and sits behind the panel when I'm listening to the stereo (the front center channel is removed as well). Good luck and don't give up!