help with port size/lenght

[heckvr4 2]

ok ,so i got a box (not really square, its a pentagon) made out of 3/4mdf , i got 5.09 cubes of air space with out the sub in (sub its a 15"fi btl)

how big of a rectangular port do i need ? its this called port area ?? i had planned to have it 12.5wide x 5tall x 24 long... tuned to 33hz... does this sound rigth ??

please help me out...

Edited March 1, 2010 by heckvr4