What are the levels set at on your HU? Try setting everything back to ZERO and give that dreaded "LOUD" button a try.
I bet your box is the problem. Maybe there is a way to Make it smaller to test sizes. Dave might have a suggestion. I wouldn't stuff it though. I think the .5-75 area would be best suited.
Keep us posted and good luck.
Check the gains on the amp as well.
