Sound is better when I stand up?

@paradisecom Reference 3a MM Gen 2. I've had iterations of reference 3as for many years. They are in phase and the tweeters are on the outside.

@designsfx The speakers are 8.3 ft apart and my listening spot is 10 ft from both woofers.

I do appreciate everyone trying to help. This is more out of idle curiosity than any burning desire to rectify the situation. It could be that when I stand up I'm also getting the reflections from the back wall, whereas when I'm sitting down, those reflections are absorbed by the chair. It is a small room after all.

@simao 

I know what it’s like to work with a small room- you can see mine under user/systems. The tweeters in my speakers are above my head while sitting and it’s no problem. The image is centered and at a nice height. At first I would say to move a few inches further back but it sounds as though you’re very close to the wall already. Needs further examination 

holmz no headrest, but it is a wingback. I wonder if that’s an issue

@simao
What is a wingback?
Is there a image of the model of chair?
(If there is some place for sound to bounce off of it can cause a problem.)

Have you tried a simpler chair, like a dining room chain, in the listening position?

Try standing up and moving rearwards so that your back is against the back wall… Does it also sound similar to the sound in the chair?

It's the wingback!

move a short back chair in same position, see what difference!

Have you treated your ceiling with acoustic panels yet?