I currently have 15" sub in sealed box but thinking to change it to 12" ported or 2 10" ported. I want to put 15" ported but the box is too big.

Just wondering what size sub and what type of box you are using? Do you have the sub facing the driver or facing the trunk and were you place the box? Do you leave the ski door open or close?

 

JL 10w6 in a sealed enclosure. Custom fiberglassed into the rear quarter panel...sub is facing diagonally rear. Sub bass is generlly non-directional...so direction your box is facing shouldn't matter a whole lot. I've got a coupe...so no ski hole....but I leave my rear seats up.