k, lets say i have a speaker with xmax of 10mm, in a 3.0 cubic foot box, wanting to be tuned to 30 hz. Height is 13.5", and width is 3". Whats the length? With the formula i use i get like 12", with an online calc I get like 33".. so Jmac, or one of you that actually use the formula please let me know which one u use, and what u came up with. thanks..