Here is a simple and interesting design of 3d printable DIY speaker in tube horn configuration.
Detailed guide, files and BOM can be found at:
http://www.instructables.com/id/3D-Printed-Horn-Speaker/?ALLSTEPS
Detailed guide, files and BOM can be found at:
http://www.instructables.com/id/3D-Printed-Horn-Speaker/?ALLSTEPS