Where is the bass on my B&W 802d speakers?

It seems to me that you can test the Room Null theory by walking around the room. If there are nulls, there should also be points of boost, where the bass is accentuated. As is pointed out above, there isn’t much you can do about how the speakers perform in the room without major re-orientation. For instance, if they are on the 25’ wall firing in at the 16’ ft wall, put them on the 16’ wall and fire them at the 25’ wall. 
 

The reason subwoofers help is that you can move them around the room. Put the subwoofer in the listening position and move around the room until the bass is strong. Then put the subwoofer in the place where you are standing and the bass will sound strong in the listening position. The subwoofer, by being in a different position in the room, counteracts the room modes generated by your main speakers. 
 

Some people find they need, two, three, or four subs in an ‘array’ to fix the problem you are having. 
 

I responded to a quiz recently, is it the room, the speakers, or the amp that makes the most difference to sound quality; 62% responded that it was the room. It truly is a limiting factor, or, shall we say, the biggest opportunity to improve sound quality. 
 

Good Luck

Good luck is correct. These speakers weigh in at over 100lbs per unit. Although they have casters on the bottom, they are ineffective once they sink into the rug

Acknowledged. I have the 801’s which have a single Woofer. No one said it would be easy. The gear purchase is often only the beginning of the journey. 
 

I remember one presentation from Dyne Audio (I think) that mentioned a typical bass frequency sound wave was 30’ in length which means that unless your room is at least 30’ deep, the sound wave ‘high’ will bounce back and either reinforce the succeeding bass note ‘highs’ or level (nullify) them. The subwoofer’high’s and ‘lows’ are frequency and distance sensitive. Avoid offending bass frequencies, no nullification; move to a different distance from the speaker (or the wall), and again, the nulls disappear. It is these facts that any solution must address. 
 

Bass traps, ‘catch’ the rebound signal off the back wall, and solve the null problem by preventing the interaction. Seems a cleaner solution to me, but I listen near field at the moment, so I’m not experiencing what you are right now. 
 

Again, Good Luck. 

FWIW jasonbourne71 makes a much- overlooked observation, that is the importance of the location of the listening position can greatly affect the sound you hear from your speakers (although I disagree with his suggestions for speaker placement). 

The absence of bass information can direct your attention to the higher frequencies and making them sound brighter than they would if your bass FR were neutral or slightly boosted. 

Your listening position could be in a bass null and moving it forward or backward could possibly solve both of your audio problems if you put it in in a neutral zone or a small node. Ditto for moving your speakers out further from the wall than you presently have them. You might just find a bass node to solve you bass issue and actually improve your treble response and bass clarity.

I know zip about your electronics beyond a perception that I gained from reviews that they might be, sound wise, less than ’warm’ and exacerbate problems when connected to speakers which might also be less than ’warm’. IME brightness can often occur from this syndrome as manufacturers are focused on maximizing imaging potential by over emphasizing the mids thru high frequencies. Folks caught up in this tend to buy separate components with similar design goals and end up with a bright system. 

FWIW, if your room dimensions as listed mean you have a 6 1/2ft ceiling this might in and of itself create problems. I’ve never heard a room with so low a ceiling, but I could imagine that it would give you some increase in first reflections and tilt up your highs. I have no ready solutions suggestions for that. 

FWIW, using an equalizer as a tool if not a permanent component might be helpful to find the frequencies which need to be changed to get you where you want to go, sonically speaking.

Get a couple of subs as that can really damp room nodes, move the main speakers around, move the whole rig into a better space.