Have you ever tried to put a speaker in a drop ceiling? Those ceiling tiles just aren't strong enough to handle the weight of most speakers. Use this bracket, which rides on the "T" rails on each side of the ceiling tile (2 foot spacing). Then you have a sturdy round backing that the speaker mounting tabs can grab hold of.
Formed sheet metal T-bar bridge to reinforce T-bar drop ceilings. Use PB-6 for 6.5" in-ceiling round and PB-8 for 8" round speakers. For open back speakers like the SC-800 use the snap in PE-8 Plenum Dome for Fire Rated applications.