Millertime1028

15.4 cu/ft is after all displacements. I wanted each 18 to theoretically see 7.5- 8 cubes net each. Ports are exactly 22.1 inches long achieving a tuning of roughly 30 hz. Make sure when you buy the sono tubes that you measure the inside diameter as sometimes they are not the exact diameter that they are listed as. Can be off as much as .75 inches. I've ran BTLs for a short time in the box you see in my vid's with good results. Box placement played a big roll on this setup as far as #'s and peak freq went, so if you have some room to play with, do some testing and see what works best for your specific vehicle.