Recently at an installation some in-ceiling speakers were placed inside the ceiling but not secured using their factory supplied mounting system. At some point these speakers have been either moved or vibrated enough to fall through a ceiling tile, which could ultimately have let to injury or worse of a person(s) below.
We remind all technicians that unless a device can be mounted securely, in exactly the way in which it is designed to be mounted, that no item should be left unsecured inside a ceiling or on a wall where it could ultimately fall at a later time.
If in doubt, stop work and contact a senior technician to discuss better ways of mitigating possible dangers from ceiling mounted or wall mounted devices.