The role of a loudspeakerA changes loudness, B reduces sound dispersion (reasons for selection)
If one is just a trumpet shaped, no power supply is to reduce sound diffusion; a power amplifier is to amplify the sound and then put out by the circuit (such as square handheld, which changed the propaganda horn) loudness (of course, the trumpet shaped cylinder of the front also reduce sound diffusion effect just change, loudness is dominant).
A power amplifier is to amplify the sound and then put out by the circuit (such as square handheld, which changed the propaganda horn) loudness (of course, in front of the trumpet shaped cylinder that has reduced diffusion of sound effects, just change the loudness is dominant).
To see what ~ ~ ~ if amplifier is a megaphone horn, no power supply is to reduce the diffusion of sound;
