That's what I need !

So say a 3' x 5' baffle on the floor.....
a = area = 15 sq.ft.
r = radius = (15/pi)^0.5 = ~2.19'
d = 2 x r = ~4.37'
Fc = 565/4.37 = ~130Hz
Since it's on the floor Fc = .707*130=~92Hz
-3db = .707*92=~65Hz
Sound reasonable ?