For future reference OP, most people will do research BEFORE buying equipment.
You got 2 15's shoved in a space where 2 12's would have worked much better.
Will sealing up your box help a little? Sure, but it still won't be comparable to 2 12's in a properly sized ported box.
Everybody here is being a little hard on you because, well, you deserve it. But don't worry, odds are all these guys calling you stupid started off knowing just as little as you do (I know I did).
Hopefully you realize that some people here are giving you good advice and you learn from this mistake.