First off, I would like to thank you for any help or insight. I've decided in the next few months that I would like to build a subwoofer. So first off I need a driver. I was thinking a nice 15" sub. The tempest seems like a nice woof to use any opinions? This is my first real DYI project other than a pair of speakers I made when I was fifteen(I'm 20 now). I'm pretty good woodworking wise and my father has been a cabinet installer and a carpenter for about 30 years so the box design/build aspect is no problem. I can probably get all wood etc. for free. I've also built and installed my car audio system with great sucess. The hard part for me is calculations. I can do the math but I need the formulas. Performance wise what could I expect? I would like a ported design tuned to about 20hz or lower. What size port and box do I need if I were toget a tempest. I'm mostly interested for ht performance. my current system is as follows: 32" jvc d-series TV paradigm reference 40's paradigm studio cc paradigm studio adp surrounds marantz sr-7000 anthem mca-2 amp pioneer 5-disc dvd player dae-woo vcr and a energy microstar 12.1 for the bass the microstar is a great sub but low end performance isn't the best as it tends to roll off after about 25-30hz. it hits about 102-105 db at it max(servo circut prevents it). for music it is awesome though. power for the new sub is not a problem either as I can get marantz monoblocks at cost.