The active ingredient in many acoustic panels is Owens Corning acoustic panel, available at many hardware stores in 2x3 ft panes of 1" or more thickness. Its a whole lot cheaper and educational to try a couple of those in different places and figure it out on your own. Frankly no professional can do any better unless they are on-site and able to hear your room. Unless you think they somehow have divine powers of observation, teleportation, or whatever. Which some here do. Not kidding. But for all the rest, DIY.
Typical places to try are first side wall reflection, front wall between speakers, and to damp flutter echo wherever two parallel walls are reflecting back and forth.
This will cost maybe $20 and take maybe an hour or so. When you get the rough idea then try cutting them to as small a size as you really need. Then finally cover with fabric.
Or pay through the nose and talk yourself into believing it was worth it.
