Have found a good (German) program for calculating housings: Bass-Cad Now I’ve played around a bit, but it’s all a mystery to me! If I enter the recommendation of Ground Zero, there’s the drawing: -3 dB at 34Hz and max 8dB at 52Hz?? Does this mean that the lowest frequency is now 34Hz …. If I play a bit I also get to -3dB at 18Hz and max 0dB at 51Hz What should I do? Which values should come out of this? Is this ever a good (German) program for calculating housings: -3dB at 18Hz and max 0dB at 51Hz What should I do? depending on my possible space/volume in the car? Maybe someone can help me! Have a box in the car below, which, however, is so big with 250L that I can not get my back seats in more. But would like to have it back again!