I have a duel 2 ohm fi btl , with every extra avalible , speaker made for spl . I have it hooked up to a bb2400.1 , with the big 3 upgrade a yellow top bat under the hood , 4 gauge wire for aps's positave & negative , no cap and stalk alt. only one battery . but i have it in a box 2.5 qu ft . tuned at 34 hrts only hitting 139.7 . the kids doing the spl test were making jokes about how low it scored , saying that there friends are hitting 141's with there 12. now there putting on a comp in a few weeks and i wanna prove that fi's btl , can do better. i just dont know how high i should tune the new box .