That's pretty big for any 12" made after 1995...

The first step in building a box is measuring the space you have available. If you want to put it behind your back seat, measure the height and width of that space. No good building a box 14" tall if you only have 12" of usable height.

 

Youll get a good response curve for it for sure, dont worry make your 2 cu.ft box if you have the space.

 

I have the space a Minivan right now with the back seats out of it, I have one more question about the terminal is there anyway to do it without a terminal I think this is where I'm going to have trouble getting it to seal good around the ternminal? Can I just drill a hole for the speaker wire and ruin it through the hole there use some really good glue to seal it there?

 

For the box design one great website is the12volt.com. The link is below.

Subwoofer Enclosure Calculators, Fraction to Decimal, Parallel, Series, Port Length and Volume Calculators

 

Drill a hole that is a fraction smaller than the wire, put silicone around the wire and the hole, jam it through, then silicone around the wires. Don't bother with terminals.