Enclosure help!

I have a Memphis audio 12 inch 15-PR15D4V2, and i have a spare 8 inch JL audio sub. I currently have the memphis in a box by itself and was wondering if it would sound ok or better if i build a box that would fit the memphis and the JL, would it sound bad because of the speaker size difference? thanks!

 

Each sub requires different air space. Definitely build separate. If there's not enough space in one box, they won't reach their true potential.

 

I'm going to make sure that theres enough space for each sub, as if I was building a duel enclosure for two 12's, but instead of putting a 12 I will be putting the 8. The box is going to be in the middle of the back seat so the speakers or going to be vertical with each other instead of side to side so it shouldn't look to goofy.