Sound travels at 1130 ft per second . That is how you obtain the first axial in a room by adding the width, height or length by itself . Then divide 1130 by that number giving you your first primary axial . For example a room 20 feet long would give you 20 + 20 = 40, 1130 div by 40 = 28.25 hz wave . This is the freq. of the first bass wave to fit perfectly between two walls in a room 20 ft long .

Trikos knows this . I think he is just trying to simplify things .