Speaker ceiling mounts for a Polk RM101. A carriage bolt fits between the two pieces with a wingnut for adjusting the angle of the speaker.

Notice: printed vertically, the ceiling piece failed along a layer. Exact cause unknown. It is in a basement so movement upstairs could have caused tiny flexes from walking above them. I underestimated the flex along the long end. However, it could have also been due to poor layer adhesion, or too much tension from the speaker weight. Improvements pending.