Hi Hotmailjbc,
Atmasphere explained it ideally, even though most planars, ribbons & electrostatics are open back, they are usually refered to by their own terms. Open baffle normally refers to cone drivers mounted without a chamber. What design did you see specifically. I have built many speakers on my own. They place to start is the FRD Consortium. These are not tools for a beginner, but for standard designs will give you the information that you need to do designs that compete with some of the best. good luck, Tim