With 1" MDF:

31 W x 17 H x 23.64 D

4.25 x 15 port

= 4.25 cubic feet after displacements @ 35.9 HZ

... with 15 square inches of port area per cubic foot.

Not a bad box if you want to play with a 36 HZ tone.

 

Will it be loud though cuz thats what im after

 

LOL! Say goodbye to your rear-view. It's going to on your L5s.

 

Two L5 12's - 86.9 dB (+3 dB starting point with two @ 89.9 dB) / 600W RMS / 1200W total / 226 square inches of cone area

BTL 15 D1 sensitivity - 93.2 dB / 2000W RMS / 176 square inches of cone area

50 square inches of cone area is an 8" subs worth, which isn't going to make up for +1300W power handling & the +3.3 dB starting point

For every +3 dB you either need to double the cone area or power, in your case it'll be like having four ported L5 12's on 600W each, but the four 12's would be better below the port tune because of sheer cone area.

What'd you power the L5's with?

 

A hifonics 1000 rms amp

 

You're going to have atleast another 1000 watts with a Kicker 2500W @ 2 ohm - if it does 2500W @ 2 ohm.