I’ve found Mapleshades advice to be spot on. 2 are better than 1. Subs should be within 1-2 inches of the mains midrange drivers and either interior or exterior to the main speakers. Subs should face along the width of the room (180 degrees) to mains. Speakers should face the long wall with the listening position against the back of the long wall. Speaker position should be as nearfield and separated as supports solid imaging and accurate bass response.
Move your sub
Caught an Art Dudley video about moving your sub(s) from behind, beside or between your speakers to the seat end of the room. I moved my REL back so they are in the same plane as the listening position. Much better! Try it.