Seating height and bass

So my myriad of other threads seem to have me believing I have a null which explains the lack of low bass at my sitting position.

tonight I pushed the couch out of the room and used a chair instead. Bass was much improved but I realized that with the chair my ears are at tweeter height. Sitting in the couch they are several inches below the tweeter.

i stacked some books to mimic my height when sitting on the now displaced couch and started moving them closer to the speakers. I tried 6 positions starting at where I normally sit (relative to the front wall/back wall) and there were differences. However I moved that chair to the same positions and better bass in each spot (some more than others but all better than the books/couch). 
Anyone else run into this? Bass better when stating vs sitting? I wish I could borrow any pair of stand mount speakers and try this again to see if, what I believe to be poor engineering/stands for aesthetics not performance, is indeed the case. My speakers are on 24” stands but are front ported with a big 4” port at the bottom front raising the drivers up 4”+.