whats the best direction to face subs?

i have 2 15s, and the box specs im going to build are big so its either facing up or like 4 inches from the tailgate. i cant try both. which way would sound better

chittyboom, see if you can find out the xmax for those subs.  They're not included in the specs you listed on the last thread.  Xmax is needed to determine if those subs will be okay to fire upwards.  Assume that they're not capable of up or down-firing if you can't find info on the Xmax.  A few inches clearance to the rear of the vehicle is okay.

An option is to build your boxes with angles so that the sub fires toward the rear but slightly or halfway upwards, like about a 45 degree angle.  From the side the box may look something like this:

You won't have to worry about sag calculation when using an angle of 45 degrees or less, and this would give you more clearance to the rear.  And should provide better bass response in the vehicle than firing straight up.

Personally, I would work up an angle configuration.  It's totally custom, looks like you put more effort and planning into it (which you will!), and leaves more space between the driver and the tailgate.  There's a lot of info you might be able to use in this previous thread that I wrote up describing some details about building boxes with angles.  All the calculators you would need are linked in that thread.  Figure the face angle by using the depth dimension of the driver, the space you have to work with and the total volume you want to achieve.  Halfway from vertical to horizontal is the furthest from vertical you can go, and biased more toward vertical is preferred.  Like the arrow direction here:

The diagram in the previous post shows the halfway 45 degree angle, so you can start with that and if you need to utilize more of the available space in the vehicle then you would start angling it more towards vertical.  Use the calculators and make relatively easy work of it.  Good luck with the build.

The angle of the fadangle is the way to go.....

You should,nt have any problems with cancelation..... (less bass)   Ya know...

This whole calculating ...fire up, or down.....come on, build a box ..the correct size and hit it...........