So i was drawing up some plans to build a sub box, and i was wondering

Does using the stuffing actually increase the internal volume or is it a trick?

I want to build the smallest possible box for my sub (10 inch Alpine Type-R) and if I can use poly stuff to increase the volume (or what have you) then i can make a small box that takes up little room in my tiny 3 door integra trunk.

 

Stuffing your enclosure with the right amount of Poly-Fill can make your box behave like it's larger than it really is. This comes in handy if the volume of the box you've built turns out to be a little short of the cubic air space recommended for your subwoofer. Depending on how much Poly-Fill you use, you can actually vary perceived box volume by as much as 30%. But don't go over board. Because you can only use so much.

You can also "stuff it" if you simply don't have room in your vehicle for the larger box your sub demands. And adding Poly-Fill to any enclosure can clean up your bass by minimizing unwanted box resonances and at a cheap cost.

 

Would this be beneficial in a ported enclosure?

 

because of the dampening ability of the polyfill, it will smooth out the response of the driver in a ported cabinet. If the box is too small, it will also help the box behave like a larger box. A driver that is in a box that is too small will have a very peaky frequency response. The dampening effect of the polyfill slows down the air flow so that the pressure waves slow down too and the air pocket behind the driver doesn't pressurize as quickly. It allows the driver to move further in its moved before the pressure wave inside the cabinet tries to push the driver cone back out. in a ported or band-pass enclosure, even if the box is built to perfect specs, polyfil can be a great help. It helps cancel the backwave which can lead to port resonances. That makes the port whistle and vibrate