Box size and tuning for fi bl15 on 2200rms
 

Need help with what size to build ported box for my fi bl15 fully loaded in my s10 extended cab I have about 16 deep inches by 44wide by up to 48 high,mostly be playing dubstep and drum and bass. Also it'll. E driven by a aq2200 at 1ohm. Thank for any help I'm new to the box building

Well, Fi stated 3-5 cubic feet, so I'd go with 5. Remember that has to be your NET internal vlume, after the volume of the sub itself, port, any bracing,and wood thickness are taken out. You have well anough space to play with. Just come up with a sketch which isn't a cube, figure out what freq you want it tuned to, and find yourself a good online calculator. If you use 3/4" MDF, double up the front baffle and consider some internal bracing.
Use proper wood glue and course thread screws to hold it together ad voila.

To add to the above, I would choose 5 cubes because like Dukk's sig says, minimum space= minimum bass. I always built boxes to minimum suggested plans before my current one, and now am a beleiver; go as big as the mfr suggests.
Going with a slot port and trying to keep it within your size specs and 5 cubes, a box made of 3/4" MDF with a double front baffle [*these are exterior dimensions] 42" wide 21.5" high and 15.75" deep with a 3" wide, 18.5" long slot port (obviously there will be an elbow inside the box, keeping the port 3" wide for the entire length) will give you a 35Hz port tune. The thickness of wood, sub & port displacements have been figured. The only extra might be a peice of all thread from front- back, halfway up the box, halfway between the sub and inner port wall to reduce flex further. I like all thread because it takes up precious little volume and has as much pull force as it does push, unlike internal wood braces.

Thanks for the help. Probably going to start building the box in a week. Im guessing the sub will still be a couple weeks. I'll post some pics of the box build, I have one more question does any one have any experience with sub and port placement in second gen s10 extended cab for spl