I was talking to a friend at work the other day. He used to be into car audio big time about 10 years ago. Anyways, a friend of his had a 94 S-10 Reg Cab, and they wanted to put 4 10s behind the seats. As you could imagine, space was an issue, so my friend discussed it with an installer at a local shop. He said that in theory, if you had more than one sub in a box, you would need only 1/3rd of the original space for the next sub. As in, if you had a 1 cubic foot box for one sub and you wanted to add another, you would only need to add another 1/3rd cubic foot to the box.
I was wondering whether this actually worked this way, and if it does, for more than two subs in a box, would you add a 1/3rd of the 1/3rd you added for the second sub, or a 1/3rd of the total space of the first two subs. My friend just fudged the theory and added 1/3rd of the box space for the first sub for the third and fourth sub.