Building a box thinking About putting some speakers in it to balance it out since I only got one sub, would having the speakers near the sub be a bad idea? Weather I seperate the boxes or not?
Another question 13.5 in jl w7 how much volume should the box have

 

http://mobile.jlaudio.com/products_subs_enclusure.php?series_id=10 <<< Link to JL recommended enclosure volumes.

You don't want to install a set of speakers in the factory locations? You could do as you're proposing, but I would suggest that they be put into their own separate box/chamber. If not, every time your new sub thrusts outwards, creating negative pressure in the box, those other speakers are going to be sucked inwards. If the sub is going out to play 30-100Hz tones, those speakers will doing the same when playing the 100Hz-250Hz portion of that same bass sound. So while the small speakers are trying to move out, the air pressure inside the box will drop, and they'll have to work against that. They'll probably heat up much faster.

 

Ford Windstar - Realm of Excursion

^click that link and scroll through the pics, you see that he build a bunch of beauty panels where he also mounted 5X7" DD speakers that are NOT part of the acual subwoofe enclosure. you can do something like that

 

thank you very much tragic this is my first box! wish me luck!!! FIBERGLASS HA!