A compression driver produces high frequencies; the horn shapes and projects them. Together they deliver the clear, far-reaching sound that PA systems, paging systems and many full-range cabinets rely on. They must match mechanically and electrically, and the driver must be protected from low frequencies. This guide walks through each decision so you can pair a driver and horn with confidence, whether you are building a new system or replacing a failed part.
A compression driver uses a small, light diaphragm, often titanium or a polymer, driven by a voice coil and a strong magnet. The diaphragm sits behind a phase plug that "compresses" its output into a narrow opening called the throat. On its own, a compression driver is not very loud and sounds harsh. Attached to a horn, which gradually widens from the throat to the mouth, it couples efficiently to the air. The result is high sensitivity: a horn-loaded driver can produce much more volume per watt than a typical cone tweeter.
Common throat exits are 1" and 1.4"/2". The driver's exit and the horn's throat should be the same size. A mismatch creates a step inside the sound path that causes reflections and uneven response. Adapters exist, but a direct match is always better.
Mounting can be screw-on (threaded) or bolt-on (2- or 3-bolt pattern). Screw-on drivers have a threaded neck; check the thread specification listed by the maker, because similar-looking threads are not always interchangeable. Bolt-on drivers attach with bolts through a flange, and the hole spacing must line up with the horn. Check both throat size and mount type before pairing a driver and horn.
Most drivers are 8 or 16 ohms. In a two-way cabinet the crossover network is designed around a particular driver impedance, so a replacement should normally match the original. In a stand-alone horn system, impedance affects the total load the amplifier sees when several horns share one channel; see how to wire multiple PA horn speakers for the math.
Use RMS (continuous) ratings to match your amplifier, and leave headroom. Peak figures describe very short bursts and are not a safe guide to everyday use. Because horn-loaded drivers are efficient, they rarely need large amounts of power to play loud. In a two-way cabinet the high-frequency section usually receives only a fraction of the total amplifier power.
Compression drivers can be damaged by low frequencies. Bass makes the small diaphragm move far beyond its design limits, which can crack it or burn the voice coil in seconds. Use a high-pass crossover at or above the driver's recommended frequency. Typical crossover points range from around 1.5 kHz to 3 kHz for larger drivers and higher for small ones, but always follow the specific driver's recommendation.
Passive crossovers sit between the amplifier and speakers and are common inside cabinets. Active crossovers split the signal before amplification and let you use separate amplifier channels for lows and highs. Either works; what matters is that the driver never sees full-range signal. A simple capacitor in series with the driver offers some protection but is less precise than a proper crossover.
Horns are described by their coverage angles, for example 90° horizontal by 40° vertical. A wide horizontal angle suits audiences spread across a room; a narrow angle "throws" sound farther and suits long, narrow spaces or outdoor paging. Horns with a larger mouth control directivity down to lower frequencies, which helps them blend with a woofer at the crossover point.
For paging and announcements, round or rectangular all-weather horns are popular because they are rugged and project voice clearly. For music, a wider, smoother horn generally sounds more natural.
For outdoor use, choose units rated for it, and aim horns away from microphones to reduce feedback. Mount horns with the mouth level or slightly downward so rain does not collect inside, seal cable connections, and use outdoor-rated cable. Point the horn at the listening area rather than at walls or hard surfaces that create echoes.
Common signs of a failed driver are no high frequencies at all, a buzzing or rattling sound, or a thin, distorted top end. Before replacing anything, confirm the crossover and wiring are intact. When choosing a replacement, record the original's throat size, mount type, impedance and power rating, and match them. If only the diaphragm is damaged, some drivers accept a replacement diaphragm, which must be the exact model made for that driver. Our guide to replacing a PA or DJ speaker driver covers removal and installation steps.
Products to consider: the 1" compression driver, 8 ohm, the compression driver with titanium diaphragm, 16 ohm, and the all-weather paging horn throat. You can also browse all PA horns and compression drivers.
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