Normal break-in via use, not range sweep.Did you "break in" the sub? I know when I initially installed mine I did not get a lot of bass from the back. Once I started to play a sweeping rang video found on youtube I'm finding the bass response to be more noticeable after just a few hours of "break in". I did not stuff my enclosure with fill and I only used hot glue to seal up the existing holes.
Break-in refines the sound, not makes bass go from zero to boom. There should be bass from the get-go.