Ok how do i figure out cubic feet when trying to build a subwoofer box for my 12in alpine. . the specs say 1.7?

just multiply the lxwxh and you get the cubic feet. for example, if your box is a cube, the length of each side is about 1.19 feet because 1.19*1.19*1.19~=1.71. you have to make sure that those are the internal dimensions because the wood that you use will have an added thickness, so your outer dimensions will be larger that 1.19 per side. also, you will want to look up the port size because too small of a port will whistle and too large of a port will make the bass sound sloppy.