I agree with everyone mentioning judicious use of the correct panels. In most listening rooms bass is biggest problem. Most retailers make bass traps that scatter/diffuse over a certain frequency to help keep rooms from being over dampened.
The room is the most critical part of a system. I was reminded of this recently when listening. The door behind my listening position that I usually keep open, I closed. This moved the reflection off the back wall behind me up about 10 feet. Sound was horrible. Soundstage collapsed, and the sense of openness disappeared. Opened the door, back to normal.
I’m sure the door closed with the correct application of panels could minimize the difference. For now, I’ll just keep the door open.