Compression Drivers and Horns

A compression driver (CD) is a professional loudspeaker driver usually intended for mid or high frequency use with waveguides or horns. They can be thought of as similar to hifi dome tweeters in that they have a dome diaphragm and a motor. The main physical difference is that the dome is coupled to an exit tube via a phase plug where the dome is large than the exit. Hence it has a compression ratio, defined as the ratio of the area of the dome to the exit.