sorry dude. i was thinking you had two subs but i see you only got one. you should try to stay away from slot ports in a small box. see about getting some areo ports, they are only 10 to 12 dollars each. you don't need any more port area then that. do you have the sub ran at 1 ohm? if you are just after spl, you need a small box. if you want some good lows built a big box. try do build a cheap box just for testing. try to make it as square as possible. try sub and port on the same side. move the box in all directions when testing(placement of box makes a difference. point the sub back,up,forward. then cover the port and put them on the side of the box. move it all around etc.