Open baffle designs result in sound eminating from the front of the driver as well as the rear of the driver, however, the sound coming from the rear is out of phase with that coming out the front. That sound which is eminating towards the sides of the speaker, both front and back, meet at the sides of the speaker and cancel. The result is that there is a much lower output from the sides and top of the speaker than from the front or rear. This results in less side wall and ceiling early reflections than a non open baffle design.
Check this out:
http://www.kettering.edu/~drussell/Demos/rad2/mdq.html
Retsel