Here down below is several speaker box plan schematics from Fedora Audio. Hope this help you to create an ideal speaker for your events and projects!
Cubo 18 Inch Speaker Box
Full version schematics: Cubo 18 schematics speaker plans
Dynacord Speaker Box 18 Inch Long Throw
Full version schematics: Dynacord Long Throw Speaker 18
CBS Trilogy Speaker box 118
All of speaker plans schematics and measurement can be downloaded from Fedora Speaker Plans