I have a 3.3^3 box tuned to 32hz. I would like to tune it lower. I had the box before I got the Brahma so how would i do this. I was thinking of adding a little bit of poly fill to the box to make it seem a bit bigger.How would i go about tuning this box lower for this sub. Would I just add a few inches to << this little wall or what, and how many inches of wall would I need to tune to around 28 hz or the best hz for this sub? And would i need poly fill or what ?