Mark, I rarely agree with pmbuko, but I ran away screaming. I don't think you should ever go back into that room again.
So much for testing speakers in anechoic chambers!!
Try painting the door red.
That having been said, I don't think your room would look like a place of human habitation if you did what you must to damp those evil harmonics. I'm looking at what happens at 60, 250, 800 and 2.6K Hz, and wonder if you've been playing with any singularities?
Also interesting are those wild peaks at 50, 100, and 3K - 8K
I don't know how you'd "tune" that room - damp it at 50, 100 and 3K-8K, and pump it up at the other frequencies.
Maybe you should get an equalizer.
