Way is it that when I see cars in magazines they have there high performance subs' magnets on the outside of the box instead on inside like normal? Is that a isobaric setup or is it for display? I am buying my 2 jl 12w7 soon and do not plan to isobaric them. Will mounting them with the magnet out of the box improve or reduce performance?

Isobaric mounting uses 2 subs mounted facing eachother. The most benificial purpose for this is to reduce box size. When you mount subs like this, the airspace is HALF as much as one subs need. So if you have a sub that needs 2 cubic feet of airspace, you can mount 2 subs in 1 cubic feet of space with an isobaric set up. Some competitors just mount 1 sub with the magnet end out for mostly looks, and it usually sounds the same as if mounted the other more common way...

Just as XtremeRS said...The only reason when 1 sub is used and mounted outside of the box, is for looks. The air space needed is still the same.

Actually if you want to get technical, you can build a little bit smaller box if you face you sub with the magnet outward, because the magnet/frame assembly takes up some airspace. So you can save some trunk space by facing it outward, but it is minimal at that...

but doing this I will still get the same sound right? I won't get an inverted sound wave?

inverted sound wave?

yes, due to sub being faced the other way. Wave mechanics

wire out of phase(plus to -, - to +)

god damnit raizen, take that damn pic of the floating girl off already. it has nothing to do with cars....besides, it freaks me out every time i scroll down the page and slide past it ;P

The only time you have to worry about wiring out of phase is in an isobaric setup. By just moutning your subs firing into instead of out of the enclosure you don't want to wire them out of phase, it will throw your sound off. The reason you do it with an iso setup is so your cones don't smack into each other and work as 1 large sub in unison. I think depending on the size of your subs you lose (someone correct me if I'm wrong) about .1 to .3 cubes of airspace for the basket/magnet. Nothing signifiacant but if you have some very airspce dependant subs it can make all the difference. But you said your going with JL's so you won't need much space at all, most JL's are designed to work in minimal space and produce alot of sound.