the solution to your problem is to place Tube Bass traps in the space, for more details see the page:
Probably youll find some good
Suggest you read the whole thread.I have a small dedicated room, 11x11x11, with a 3x3 window on one of the side walls. I have no treatment now, but have been looking, and I am going to try the ZR panels. I wonder how many I will need . . . two big ones, four 24x24 . . .? The explanation of how they work strikes me as plain old gobbledygook -- a bunch of complicated pseudo-scientific nonsense to confuse a reader -- reminds of the MIT "poles of articulation" nonsense -- which cables many like regardless of explanation. However, it seems as if, regardless of how they work, they do apparently "work," which is all that I care about. I don't need to know how the circuit boards in my Pass Labs X250.8 work, just that they do. I am interested to see what the ZR will do for my reflective room!