Quote Originally Posted by Ian Mackenzie View Post
You might be able to moderate the problem with Minidsp EQ.

I had a similar problem in an apartment living room 20 years ago that was 4 m square and solid brick and concrete slab. The bass tended to hum. I found turning down the bass below 50 hertz on one channel helped.
I have a 10-15dB suckout. There is no way to fix the dip with EQ, it is a self cancellation. I lumped 9 inch 30"x48" think broad band panels in the corner and all they did was add 0.5-1dB. I would have to fill every wall corner of the whole room with that to get back that 10dB.