Every room favours a few bass notes. You can find yours with a tape measure and one division.
Play a slow bass line in an ordinary room and one note will jump out. It is louder than its neighbours, it hangs on after the others have stopped, and it is always the same note. That note belongs to the room, not to the loudspeakers.
The arithmetic
Sound travels at about 343 metres per second. When half a wavelength fits exactly between two parallel walls, the wave folds back on itself and stands still. The frequency where that happens is the speed of sound divided by twice the distance between the walls.
For a room four metres long, that is 343 divided by 8, or about 43 Hz. That is close to the lowest F on a bass guitar. The same room will also favour 86 Hz, 129 Hz and so on up the series, and its width and height each add a series of their own.
What to do about it
You cannot remove a room mode, but you can decide where to sit in it. The boom is strongest against the walls and weakest about a quarter of the way into the room. Moving a chair forty centimetres often does more than new equipment.
When we design a room from nothing, we choose proportions so the three series interleave and no two modes land on the same note. That is the figure we draw first.