.....I just recalculated the interior dimensions of my box: Upper section - 9.4cm X 21.6cm X 23.8cm. Lower Section - 6cm X 19.4cm X 26.7cm.....and got 7.94 Liters of volume [uh-oh!] I'm going to install it but would like to start building another box modeled on the boxy shape of the BSW subwoofer box which looks to contain a little more volume and then compare the sound between the two.

Does anyone know the outer dimensions of the BSW custom subwoofer box for our X5?