Bass Response

Can you please advising me as why do i hear so much more bass or fuller sound when standing at my listening chair? The bass seems to drop when i seat on the chair. I've 4 Blakhole bass traps at 4 corners of the room. Is there anything which i can do to kind of pushing the bass lower!!!?
Thanks Samhar
The speaker outside rear corners are about 3 feet away from the back wall.
I've tried Cardas speaker placement method last night and found that it made very little difference in the bass response at the seated position.
I've also bass tested using Jennifer Warnes Deep Way Down song. There was plenty of bass at the seated postion which make one thing that an active sub is running in the room. (Very nice, I like it!). However, with certain songs, the bass is still flying half way height in the room.
Updated Mode Cal base on precise room measurements...
Can someone please explain what are the main issues in my room and recommended treatment methods? It seems there are freq. jumps on H values
Your help will be much Appreciated!

L 16.08 H-4 287.1664549
W 14.1 L-5 175.6840796
H 7.87 W-5 200.3546099
Cu.Ft. 1784.34936 H-5 358.9580686
L-1 35.13681592 L-6 210.8208955
W-1 40.07092199 W-6 240.4255319
H-1 71.79161372 H-6 430.7496823
L-2 70.27363184 L-7 245.9577114
W-2 80.14184397 W-7 280.4964539
H-2 143.5832274 H-7 502.5412961
L-3 105.4104478 L-8 281.0945274
W-3 120.212766 W-8 320.5673759
H-3 215.3748412 L-9 316.2313433
L-4 140.5472637 W-9 360.6382979
W-4 160.2836879 L-10 351.3681592
L-11 386.5049751
Firstly, have you considered reading Dr Floyd Toole's book? It will educate you about room physics and help you understand why you're hearing what you're hearing. A little education can go a long way towards effectively treating your room to get the sound you want.

Secondly, have you a room mesurement tool such as the OmniMic, XTZ, or REW so that you can take "Freq VS SPL" and "Reverb (RT60)" or "Bass Decay" measurements? These tools will help you see what your ears are hearing and help diagnose what the problem is. Without tools and data you're blind and only with infinite time and trial and error will you get things right.

Lastly, bass is always stronger near or at a surface so when you stand up from your chair your head is closer to the ceiling (than it was when sitting) so unless your ceiling is really tall you should hear more bass. Similarly when you walk around the room and go close to a wall. This can be verified with a basic Radio Shack SPL meter.

Read the book first though . . .
Thanks Kevinzoe
I'm currently chewing through Master Handbook in Acoustics with over 400 pages! Very good reading...
I have more understanding on room modes and what they meant. However, i still can't work out a solution to my bass fly issue. I think toward the end of the book will have a chapter on room, acoustic and speaker placement topic
I'll post my findings hopefully in a couple of months!