need help for new box!

[nracing]

hey guys im kinda newbie on the box subject i have a bravox 8" subwoofer in a bandpass box, is pretty good but i think maybe a ported box will be better, but i don't know how to do it and how to tune the port, i like spl but i really don't know how to tune the box. im not really sure but this is the sub http://www.bravox.com.br/produtos/premium2e_psw8.asp

if anyone can help me it would be really nice!!

thanks!