I've made all the cuts for a 18" sonosub and before putting everything together I just wanted to make sure I didn't do anything wrong. Here is what I have: Two 1" MDF bottom plates (total 2") One 1" MDF top plate 46" length (43" internal length) One 4"x 25cm port 5 lbs polyfill Old SVS driver Amp - to be determined I downloaded LspCAD and it shows 21Hz tuning for this design. Does this seem right? I am also planning to experiment with different port lengths to see (hear) the effect and decide on a final design before I build its twin. Any suggestions are welcome.