Since it is the room you will need to try moving the speakers around. I would expect there is node that is getting excited. Have you tried any corner bass traps or acoustic treatments? Where the corners meet is where bass build up can happen.
Help with ringing bass from Dynaudio C1
I recently replaced a pair of Silverline SR17.5's with some Dynaudio C1's. I love the Dyn's, but one thing is driving me crazy: on some passages with a deep bass drum (e.g.,Young People's Guide to the Orchestra on Mr. Britten's Orchestra), the bass starts ringing, obliterating other frequencies and sounding very much out of control. I have tried putting an acoustic panel in back of the speaker. That helps some, but the bass is still resonating too much. It sounds like one note in particular, but I can't say for sure.
System:
PWD mkII via ethernet bridge
Bel Canto Ref 1000M
Audioquest Sky XLR, & Volcano speaker cables
Audience AR6T conditioner
System:
PWD mkII via ethernet bridge
Bel Canto Ref 1000M
Audioquest Sky XLR, & Volcano speaker cables
Audience AR6T conditioner