A properly built steam shower will have a slope to the ceiling. This is to keep water droplets from forming on the ceiling and dropping on the occupants head. These droplets will be colder and don't feel pleasant when they contact the skin.

So, where does this water on an angled ceiling go? It clings to the surface of the ceiling and rolls down to the lower side of the slope, down the wall, and into the drain. In the process of doing this on your job it will roll right into the trim ring of the speaker where it will either drop to the person below or will enter the speaker enclosure. I've always installed in-wall speakers in steam showers, up high, on the wall with the highest ceiling point. And I never use dual tweeter speakers anywhere. Sometimes Mono is your friend (small rooms, showers, and anywhere outdoors).