A Compression Driver is a type of audio transducer designed to be coupled to a horn.

Unlike a conventional loudspeaker, the compression driver does not radiate sound directly into the air. Instead, its diaphragm generates sound in a small, high-pressure chamber in the "throat" of the horn.

The horn acts as an acoustic transformer: it takes the high-pressure, low-velocity sound from the throat and gradually adapts it to the low-pressure, high-velocity ambient air.

This coupling process optimizes energy transfer, resulting in extremely high efficiency. For this reason, compression drivers are the standard choice for reproducing mid and high frequencies in PA systems, stage monitors, and any sound reinforcement application that requires high sound pressure levels (volume) with low amplification power.