Just had 2 10" JL Audio Subs installed in my 2014 F150 crew cab should they fire up or down?

 

It's a matter of preference. Usually down fire boxes are easiest to design, and less likely to get damaged. The bottom of the seat frame will sag under weight (like a trampoline) so you wouldn't want a large up firing box with minimal clearances under the seat

 

Was thinking the same thing. Thanks