yes guys i did a search and the 1501d seems to have no ssf. i was also reading that i dont need one unless im using a ported box which i plan on doing for 2 15 L5's with a whole lot of space to use up (entire back hatch of my explorer) can i get a ssf to add to my amp or do i need a whole new amp with a ssf? also what does the ssf do and why is it only needed when going ported?