PROAC D48R Bass Booming

I have a friend who have the same problem with
his proac d40r, his temporary solution was to put towels
below the speaker port, essentially just laying the towels
below and not stuffing the port itself. He said it minimized
the booming.

I have the d40R (in my opinion better) and I ride them with the Accuphase M-8000 mono. I solved with (see photo my profile). Another excellent one was to use Gaia IsoAcoustics (they work great).

Stanislao

gnanasekhar,

One more thing to consider--if the floor in your listening room is a suspended wooden floor, the floor could be acting as a giant sounding board which could be at least part of the problem.  With such flooring, the speaker should not be coupled to the floor (e.g., by using spiked cones), and instead, isolating footers or platforms should be used; you want something that will absorb/damp the bass energy that is shaking your speakers rather than coupling that energy to the floor.

@gnanasekhar,
Are the speakers placed in front of the long or short wall?
Can you move them 24" from the side wall? Also Can you move them 50" from the front wall. Also try with the classic ProAc toe-in; which is to angle at the listening position with the "inner" side wall slightly visible from listening position. If that does not work, try to aim them straight ahead.
Looking at your profile, I think you have marble/til floors and thick concrete walls. So bass trapping in the corner will also help. The bass on these babies is certainly not "loose". It is super tight if the right.
The IsoAcoustic Gaia II will certainly help providing definition to the bass.Try to adjust the speaker position. The more you get it "into" the room, the less bass. Do your best before your decide to part away with this PHENOMENAL loudspeaker. Good luck!

@milpai 
The speakers are placed in front of the longwall and are placed on Tile floor.  What about the Herbie products