I haven't read many posts on this thread but my truck did a legal 142.2 @ 40 hz SEALED at a DB Drag event in Indy, IN. With that setup just a single red top battery from Autozone, stock alternator, one DB Drive PT2000.1D, one DB Drive PLT15WD, and box was 4 cu ft at 39.5 hz with a stupid ~25 cu in port area per cu ft. But with my current setup I hit 145.8 SEALED at an eCrack event in Mt Vernon, IL. With this setup I just had same single red top battery, stock alternator, one DB Drive PT2000.1D, but two DB Drive PLT15WD's and box was 11.37 cu ft tuned to 40.17 hz with a low ~14 cu in port area per cu ft. Both boxes were built rather quick with no 45s and just minimum bracing. 145.8 probably isn't close to being the loudest in that category but it is what it is. All giving decibels are from a Term Lab used at both competitions while being completely sealed.