So ive currently have got an Fi SSD15 in a 3 cube box, ported tuned around 31 hz. it murders the lows, and theres no port noise that i can tell despite it having only about 11 sq inches per cubic foot of box volume. the problem is, there seems to be cancellation in the 50-65hz range. it hits great below that and even gets louder over 65hz until it starts rolling off around 85hz. this is in the trunk of a 2001 BMW 525i. i have the sub fired up with the port back. im very frustrated with this lack of a crucial sub bass octave. i'm about to build a new box, in the neighborhood of 4 cubes with a port tuned around 35 hz, with at least 14 sq inches per cubic foot of internal volume. should this fix my problem? i'd really appreciate some guidance here. it isnt my car's fault, because i used to have 2 kicker CVR 12s tuned @ 40hz that hit this range of bass just great. when it comes to box size, is bigger always better as long as the port ratio remains proper? could it be because my sub is fired straight up? with only aobut 4-5 inches between it and the trunk roof? help me understand what to do to get my 55-65hz range back please. i waited a month for my Fi subwoofer and ive been very pleased with it otherwise except for this one thing. thanks in advance.