I was originally going to build the sealed sandbox version sub. I just liked the idea of the sand damping the cabinet walls. But after looking at my room and everyone saying how good OB base is I decided to build the OB sub. But I still liked the idea of the sandbox, so I combined them. Will it make a difference? I don't know for sure. Would I do it again? I don't know, it has turned out to be more work than I expected.