English: Animation showing how a horn loudspeaker works. The image shows a cross section through the center of the speaker. Horn speakers are used as tweeters and midrange drivers in audio speaker systems, and in public address systems. A horn speaker consists of a special diaphragm loudspeaker called a compression driver (A), attached to a flaring horn (B) which conducts the sound waves (grey) to the open air. The driver contains a stiff metal diaphragm (blue) that is vibrated by the audio signal current passing through a coil of wire (red) between the poles of a magnet (green). The diaphragm pushes against the air creating sound waves. The horn couples the sound waves efficiently to the outside air, increasing the acoustic impedance, enabling the driver to radiate more of its power as sound waves, increasing the loudness of the sound. The diaphragm of the driver is larger than the entrance throat of the horn, creating a high sound pressure in the horn to improve the efficiency. The advantage of a horn speaker is that it is more efficient than a cone speaker; it can typically produce 10 dB more sound from a given amplifier power.