SounDrive
Pro Seller
www.soundrive.audio
Not sure that these are the "official" specs but these are the optimum enclosure specsYou have a link to xfl 15 specs like air space max min and stuff ab site don't include that info
4-4.5 cubes tuned to 32-34 hz with 14-16 in^2 of port per cube. Lower tuning does well too but isnt really needed. My XFLs are tuned at 33hz and still hit low notes (sub 30hz) with authority