In principle, different types of broadcast speakers should be selected depending on the environment. For example, in a room with a ceiling, it is advisable to use a built-in ceiling speaker without a rear cover. This type of speaker has a simple structure, is relatively cheap, and is easy to construct. The main disadvantage is that there is no rear cover, and it is easy to be bitten by insects and rodents.
In a room with only a frame ceiling and no ceiling (such as an open-frame shopping mall), it is advisable to use a ceiling-mounted tube speaker or a ceiling speaker with a rear cover. Since the ceiling is equivalent to an infinite baffle, the use of speakers without a rear cover under the condition of the ceiling will not cause an acoustic short circuit. The situation is very different when there is no ceiling. If you still use a ceiling speaker without a rear cover, the effect will be very poor. In principle, ceiling speakers should be used. However, if the investment is too large, a ceiling speaker with a rear cover can also be used. The rear cover of the ceiling loudspeaker not only has general mechanical protection, but also plays a role in preventing acoustic short circuit to a certain extent.