"ceiling mount" in the name always on ceiling, "wall mount" on wall, "directional" in the direction you want, if not specified horizontal on a table (ceiling mount acceptable). If there is going to be a dead zone in the omni pattern it's generally the "back" (where most other stuff is like ports and power). On ceiling mount the back will be able to go straight up into a ceiling, if the back is just one of the smaller sides then it's definitely meant to sit on a table.