[ringbearer3791]

i'm relatively new to this as well but i'll attempt to answer your question regarding tuning and why to tune low rather than higher in an LLT setup. The size of the port tunes the frequency response of the subwoofer, WinISD pro is a great free program you can download from on the site here and a little playing around with it will allow you to visualize how a different tuning frequency for a given size box will affect frequency response. The traditional issue with ported subwoofers comes from poor response at and below the tuning frequency. If the subwoofer is designed for music use alone then a tuned frequency of 20 Hz isn't likely going to cause any problems since music doesn't really get down that low but in HT applications there are definitely effects that do reach down into the low 20s or even the teens. The goal with a ported HT sub is then to drive the tuning frequency down below where any of the actual frequency content exists and thereby avoid the issues with driving a subwoofer below its tuned frequency. there is a wonderful treatise on why to go LLT posted as a sticky on this site which says everything i've just said with much more detail and far more eloquently.

hope this has helped.