Speaker Positioning

Hi to all, I'm loving my Naim Uniti 2 which is connected via NAC-A5. 

For or some time I've been wondering whether I need to move my Mission 783's due to some bass boom I experience when listening to music which is 'Bass Heavy' when Im listen to music sitting back in my lounge sofa. 

My my room is around 5x5 mtrs and my listening position is around 4 metres away from the speakers. I can't move the