Subwoofer bass issue


Hello all,
Looking for some direction.  Here is some background....small / medium dedicated listening room, 16' x 11' x 10'.  Set up on long wall, heavily treated with absorption (side walls and behind listening position)and diffusion(front wall behind speakers and rear walls) bass traps in corners.
McIntosh 601 monoblocks, C2300 tube preamp all on anti vibration rollerblocks and platforms, hi end Synergistic Research cabling and power cords, Sonus Faber Guarneri Evolutions paired with two REL G-2 subs....
Beautiful full soundstage with tons of detail and body, extraordinary bass...just what we shoot for right?  Problem is on certain tracks on certain albums, Dianna Kralls Turn Up the Quiet for instance, I get this crazy bass rumble that sounds like a small train going by the room.....weird thing is that on albums that the sound engineer obviously tilted up the bass output, Patricia Barber Modern Cool or Rene Marie Sound of Red, sound just awesome!  No issues.  I have experimented with moving the RELs further back, further out, closer to the mains or further from the mains and I can't seem to eliminate it.  I have stone floor over concrete with 1" thick wool rug just in front of speakers and covering most of the floor.  Recently tried "decoupling" the subs by placing them on roller block bearing devices and it help some....BTW, shocked on how beautifully this tightened up the bass in general...just didn't eliminate this occasional issue.  I tried turning down the REL output from my typical setting of 18 down to 10.....stops the problem but takes all the body and bloom with it...has anyone out there experienced this and how did you solve it?  Open to suggestions.
Thanks as always!
ptrck887
It appears that your room amplifies 50Hz:  1125ft/s divided by (2x11ft) - not a bad thing, but it will also amplify 100Hz.  I looked at my Johns Manville 2" high density fiberglass panels absorption data and they start damping at about 100Hz.  To effectively damp 100Hz in the room you would most likely need 4" panels.  Have you tried to rotate sub 90deg to project along the longer wall.  Does it change anything?  It is also possible that you have resonance issues or need bass traps.  My panels are not installed yet but just scanning frequency response with microphone shows small hump at 40Hz and large one around 80Hz.
Interesting....hadn't thought of or tried rotating and fire along the long wall vs aiming towards listening position....I'll give that a try.  I am using a combination of 6" and 4" GIK Absorption panels on side walls at first and second reflective positions as well as bass traps in each corner.  I'm also using their bass "soffits" on their sides along the rear wall baseboards under two 6" x 48" x 24" panels behind listening seat....seems like plenty of absorption going on.
Thanks
It appears that you have reflections under control.  Have you charted your system frequency response with free program "REW" and calibrated microphone.  I just ordered calibrated USB microphone to use with this program.  That can make much easier to damp the room or incorporate sub.

Are you using a turntable, CD or Streaming?
If the former, perhaps you have a bad pressing.
B
Modwright Oppo CD player and a Lumin A1 Streamer with Kenneth Lau Silver Edition Power Supply....
which track on the Krall ?
Wondering if its a Verve thing as it occurs slightly in simple Red Book format on Live in Paris track 'S Wonderful. 

On 196hz Hi Res download of Turn up the Quiet, track I'm Coffessin it occurs slightly right at the beginning and on Moonglow at approx the 30 second mark it kicks in very strong.

It baffles me because on Diana Kralls Girl in the Other Room DSD track Temptation, it has a relatively high amount of bass and no issue.  If you are familiar with Patricia Barbers album Modern Cool or Holy Cole's album Romantically Helpless track One Trick Pony, both albums the sound engineers obviously made the bass very prominent yet I have no issues...weird!   

Fortunately the REL's have a remote volume control so I can turn down the output on albums that it effects without much effort.  Just seems odd.
Thanks 
P

The Loudspeaker Calculator here http://www.hunecke.de/en/calculators/loudspeakers.html may offer some assistance

For some background on subs and their operation see http://www.ielogical.com/Audio/SubTerrBlues.php/
For just setup suggestions see http://www.ielogical.com/Audio/SubTerrBlues.php/#Setup
Great setup. The fastest solution will be to add eq / room correction on the two subs. Wont need much.An old school parametric from the pro shop, a miniDSP or various more expensive options.