Boo, welcome. It isn't the room size as such, but the fact that the dimensions are identical. When this is the case, room resonances build up at the same frequencies, making the response in the lower frequencies more uneven. If for example the room was the same overall size, but was 15x23 instead of 19x19, this would be better acoustically.
Also, a seating position exactly in the center of the room isn't optimal since there's a bass null directly in the middle. Sitting a little in front or behind the exact center, if practical, is a better idea.
