My 15s are a Peavey 115BX BW (or something, it says on the back) had is original 4 ohm replaced with a 8ohm speaker, the other is a home made that looks like its been built to same spec (ish) as they are exactly the same size, both ported, the home made has a smaller triangluar port, 3x3x pythagoras. I also own a H&K 4x10, which is a guitarists house so can't look at any firther detail, never intended to sell it so paid no attention before.
Edit: I have a Peavey black widow speaker that can go ineither, as yet I've not managed to break either or been dissatified in any way, so have not had them out to look.