If that's a 48 inch driver then the path is probably long enough.
You should realistically be looking for path lengths around 10 - 20 feet, depending on what you are trying to do. If you don't define any goals and post pictures with no dimensions or known parts you are probably going to take the long road to whatever your destination may be.
Your drawing is starting to look like a Labhorn. Look up Labhorn for a real world example of this type of horn with tons of available info. Just a few more folds and you'll be there.
Edited by diy speaker guy - 10/9/12 at 8:57am