in a reflex cabinet design you need to have an open volume of air between the woofer(s) and the vent. This volume of air is required to be open and not damped so the woofer(s) can effectively drive the vent into resonance. Damping material should be kept to the bottom sides and above the woofer/vent area if it is deemed useful to use. The fact that Klipsch have installed damping means they decided that it helped but you do not want it in the volume of air between the woofer(s) and the vent. It won't make a huge difference but in audio all the little bits add up. Hope that helps.