PROAC D48R Bass Booming

OP: If you plan to keep these speakers, Find a competent tech and have them add a volume control to the woofer circuit. They could hang the control from a wire so it comes out the bottom (where the bass comes out) so you wouldn't have to damage the cabinet. Problem solved.

@rego,I agree. And that is what I am suggesting. Placed along the 17' wall, he can try to move the speakers at least 4.5' from the side walls. That leaves 8' between the speakers which is ample for a room his size.

I will try this, definitely.

Is it really the case where the speakers sound great with most recordings, but is too boomy for some?  Could it be that it is still a bit boomy with most recordings, but not so troublesome?  I ask because any sort of permanent fix to reduce the booming will also affect the sound with recordings that you are not troubled by.  It might be the case that an equalizer will be the best approach for you--you can then do recording-specific adjustments.

It may also be the case that a set of subwoofers will work.  You can adjust the crossover frequency and thereby cut the levels of bass coming from the ProAcs and then adjust the bass from the subwoofers to your liking.

In any case, your approach of doing more experiments with placement will always be the best first step.  But, do not assume that farther from the back or side walls will always reduce the booming bass.  There could be points that are actually near the walls that will do the trick; it is a matter of finding points that reduce reinforcing nodes and cancelling nodes.  I also generally like bass traps in room corners.  

Dear all,
                I am updating the latest development.  I sold the BAT VK 3000 SE and replaced it with a pre-owned Karan KAI 180 Integrated Amp.  I tried plugging the Downward Port with Foam.  Trust me, 80% of the Bass boom is gone and now I am listening bass-heavy tracks without much difficulty.
                 My sincere thanks to all.