I have a sealed box and I was wondering what poly fill does and how much I would need (box is about one cubic foot). Also, i have a small air leak around the edge of my sub and the box. How do I "seal" the leak?
in order to seal the leak you should use some sort of thin foam/rubber gasket with self adhesive on one side (stuck to the box) just thick enough to eliminate the leak but not too thick as to create an unstable footing for the sub. apply it all the way around the opening of the box, not just where the leak is.
i dont know the scientific explanation for what the poly fill does, but, in layman's terms... it makes the sub think the internal box volume is bigger than it really is. as far as how much to use, i would put just enough to fill the enclosure without having to force it in. and that only depends on the box parameters required by the sub manufacturer.
use one to one and a half pounds of polly fill per cubic foox of volume. the fill slows down the sound waves goung out of the box and that creates the sound of a bigger box