I have had good results with using Super T CA glue for automotive plastics. They make a three different kinds, one is gap filling and very thick
, one is somewhat gap filling
, and the last is very runny and does not fill gaps
. I would probably use the thickest if there are lots of gaps, or the medium one if the seams are fairly tight. Either way you go, be sure to get some accelerator
to quickly cure the glue once in place.
I don't know how well any kind of glue will last holding a sub enclosure together... plastic soldering isn't much better in my experience. If it were me and I wanted it done right, I would glue it together, then go along all the seams with some fiberglass resin and matting - then it really won't separate!