From looking at your room photo this room is crying out for
bass traps and wall acoustic panels to control reflections.
https://www.amazon.com/s?k=wall+dampening+panels&crid=3TYRU1J1PU08K&sprefix=wall+dampening%2Caps%2C77&ref=nb_sb_ss_ts-doa-p_1_14
https://www.amazon.com/s?k=bass+traps&crid=18JR9X9I1DFU7&sprefix=bass+traps%2Caps%2C81&ref=nb_sb_noss_1