It is a science and it’s not all about absorption. If you have corners, if you have 1st reflection points, then you will need treatments. If you have bass issues, after you have tried positioning the speakers with no cure, your corner absorption pieces will need to be fairly large, small panels only deal with higher frequencies. Also, diffusers can be both a diffuser and an absorber. IMO, work with GIK or ASC or both to get a good idea on what’s needed. Also, watch the Dennis foley YouTube videos on this subject, these guys are the experts
