I had a hard time fitting a a box for a 10" sub behind the well, firberglassing a closer fit would have helped but for a 15? I dunno. I don't think it will fit there. Plus you don't want them aimed right at each other.
Putting them on one side is plenty doable, but facing each other is iffy. There is a pretty high chance of the sound waves canceling each other out and it sounding like crap.
A ten would be easy, but a fifteen? I have two 8s with getting the full recommended volume, and that's without even using fiberglass to get a perfect fit. Those 8s are for low volume enclosures though, so I'm not sure if there even is a 15 designed for that. Perhaps a 12 could be done though.
It's 40" wide, 18" high, and 19-1/2" deep. I just thought we could wedge it in somehow..
i'd have to look in my trunk to confirm my idea, but you may be able to completely remove the rear seat and then slide the box in. . . . . and reinstall the seat afterward. but i am not completely sure that the box would fit around the wheel wells in the front end of the trunk.
It won't fit between the first space behind the seat, but it will in the second space. The one I'm talking about it just behind the insulation where, I'm guessing, there is a strut tower brace? I think if the back seat came out, we could push in one side to the back corner of the trunk, then rotate in the other side? Or maybe try the same thing from behind the car?
Tell you what right now I have 1 15" and it hogs most of the trunk as in if I need to get to the spare out comes the box. I am not quite sure of the size on the box (hell, I didn't build the damn thing) but getting 2 15's would be a challenge. However it has been done. I would PM Rusty Shakelford he has 2 15"s in his trunk.