i have done a little with car audio builds but only with sealed boxes. i have just gotten into the ported boes. i am going to be using a MJ-18 because its price is just in my fairground. (college student living in mom's basement) lol. the box is going to be 10.8 cubic ft after displacements. its going to be tuned to 22hz with Four 4.3125in. by 7.31in, flared at outside end, aeroports. the graph in winISD shows this to have the most spl output for what i want. i am mainly going to be using this for watching movies and sometimes party or chill music. i am going to set the subsonic filter at around 18hz and highpass at 70hz. the air velocity peaks approx. 52miles/hour at 20.5hz. is this a low enough number for hometheater applications? the sub is going to be flush mounted. there is a .8mm over-excursion at 30hz but .8mm shouldnt be damaging right? with this tuned to 22hz i get between 119-118 dB until 22hz. between 22hz-20hz, i get 118-115 dBs. what do you guys think? and if theres something off or something i was mislead about please help a newbie out. sorry about going all over the place with my thoughts. thanks in advance for the help. ill post my whole set-up when i get home because i dont remember all of them exactly.