go to alpines site and you should get the recommended box size. the box's volume also depends on the type of box it is. sealed boxes will be smaller than ported boxes.

sealed box volume: 0.7-1.0 cubic feet
ported box volume: 0.75-1.75 cubic feet

the looks to be too big.

you know for about $30 and a couple hours, you can build your own box. that is if you have power tools and know how to use them.