I need to find out what the correct airspace is with this box. The depth is 20" with the sub facing up. The 36" is the bottom of the box. It's shaped like a "T" to fit over the wheel wells.

I know it's kinda crazy, but I need to maximize the room I have for an 18" sub I have coming in shortly. Thx for your help, Vic.

I need to find out what the correct airspace is with this box. The depth is 20" with the sub facing up. The 36" is the bottom of the box. It's shaped like a "T" to fit over the wheel wells.

I know it's kinda crazy, but I need to maximize the room I have for an 18" sub I have coming in shortly. Thx for your help, Vic.

Break it down into sections.

Top section of the T:

v(1) = l*w*h

v(1) = 20" * 48" * 9"

v(1) = 8640"^3

Bottom section of the T:

v(2) = l*w*h

v(2) = 20" * 36" * 6.5"

v(2) = 4680"^3

Total volume

v(t) = v(1) + v(2)

v(t) = 13320"^3

v(t) = 7.71ft^3

Don't forget to account for material thickness...

I was thinking the same.