thanks for this info. the next step is to build a different box. im going with a traditional sqaure sealed box just for test purpose. ill change the glue as well. i grew up using liquid nail so its second nature. i agree with all you said though. im not giving up on FI but so far its a first for me to build a box for a sub and have it sound bad. unless FI is a picky whore about enclosure and air space. Is there an air space recommended other than factory requirment you think. Personally its hard to imagine that huge sub sitting in a .75-1 cft box. Nope, I'd go with what Fi recommends. As Brendan mentioned you have to factor in the volume the sub itself to the volume of the enclosure. So say you're going to build an enclosure that is 1.5cuft NET, be sure to add the .16cuft of driver displacement for a total box volume of 1.66cuft total. For example the outside dimensions of a box that size might be 16" W x 16.75" D x 14.5" H, internal dimensions being 14.5" W x 15.25" D x 13" H. Every sub manufactured is picky about it's enclosure. The enclosure is everything to how it performs and the type of enclosure and other details can change just how picky it is. Sealed enclosures are the most forgiving and ported enclosures have to be much closer to the alignment specifications to work as designed. The more complicated the enclosure alignment (such as 4th order bandpass and 6th order bandpass) the more critical the design and build of it is but one major thing is common among all of them and will make or break their success and that's being AIR TIGHT. You said your current enclosure is 1.25cuft. How sure are you of that figure? Is that 1.25cuft including the sub displacement or not? Any chance you can post up dimensions so we can help verify the internal volume? Sorry I'm so inquisitive but the more information we have the more we can do to help you verify with as much certainty as possible where the problem truly lies.