Dimensionally there are good rooms and there are bad rooms. Few rooms are dimensionally perfect unless built or modified to comply with the following formulas:
( room formula )
If your room doesn’t come close to one of these three ideal formulas, welcome to the real world.
I need to stop right here and mention that IF it is possible to move a wall or change a ceiling height so that your room hits one of these formulas, do it. Many rooms can be made smaller to hit one of these formulas.
There are two forms of room treatments. A) absorption and B) diffusion. You will need the correct balance of both to treat any room.You will know if you need room treatment by how long it takes you to get tired of listening. If you get tired of listening at all, you need room treatments.