Just an overview of my current setup, I have 2 x SWR-1242D subwoofers which came with their factory designed ported box shown below: I am looking to change them into a custom fiberglass sealed box such as this one: I realize I may get questions like why would you bother and so forth, well reason is because I want my boot space back and this is the most viable option. My current boxes are currently taking up about 3/4 of my boot space which leaves basically no usable room whatsoever. My inquiry is whether this will be sufficient for my subs or will I simply lose the potential of my subs by putting them into these boxes. All I know about these fiberglass boxes is that the volume is 31 litres. From the specs for the sub, the optimum sealed volume range is between 0.7-1.0ft cubed. I don't understand how to measure volume, especially when it's converting from litres so any help is appreciated. Feel free to post your suggestions also. My main concern is boot space so any solution for this would also be appreciated.