hi leutz! I have a subwoffer from audiosystem. but it no longer brings the pressure forward! can you please help me there further ? the sheet at the skisack I have already taken away . must I build a different box where dié bass reflex tubes go forward through the skisack ? or do you know something else ? would also be great if one of you could send me a construction instruction for a subwoofer ! no matter what I am grateful for any help ! salute björn