Spec Sheet Preview: The Alpha Communications® RB8S speaker is a cost effective ceiling speaker and baffle (grille) combination. The model RB8S features a high-quality 8 ohm public address and background music speaker, with excellent voice and music response. The RB8ST is the same as the model RB8S, but also includes a built-in (dual voltage) 25 volt/70 volt line transformer. The RB8S series speaker is designed to be installed easily, into a standard suspended (hung) ceiling or sheet-rocked ceiling.