I have a friend who has subwoofers mated to ribbon speakers in a small, very irregular room. He uses TacT, where he can read all the frequency curves reaching the single seat sweet spot. There were big dips in the upper bass area. By some repositioning and equalizing through TacT he managed to straighten things out.
Now his play back is more than reasonably flat through 25Hz, with subwoofer in place.
Now his play back is more than reasonably flat through 25Hz, with subwoofer in place.