Paging horns are one of the simplest ways to cover a parking lot, warehouse, farm, sports field or event space with clear voice. The hard part is usually not the horns themselves but connecting several of them to one amplifier without overloading it. This guide explains how to wire two, four or more 8-ohm PA horns safely, how to calculate the load your amplifier will see, and what to check before you power everything up.
Every speaker presents a load, measured in ohms, to the amplifier. Most amplifiers list a minimum load they can drive, often 4 ohms, sometimes 2 ohms. When you connect more than one speaker to the same output, the combined load changes. Wire them the wrong way and the total can drop below what the amplifier can handle. The amp then runs hot, goes into protection, distorts, or in the worst case fails.
Low-impedance (8-ohm or 16-ohm) horns, like the ones we carry, are wired directly to a standard amplifier output. They are different from 70-volt or 100-volt "constant voltage" systems used in large buildings, which use transformer taps. Do not mix the two methods: an 8-ohm horn without a transformer should not be connected to a 70V line.
In parallel wiring, every horn's positive terminal connects to the amplifier's positive output and every negative terminal connects to the negative output. With identical speakers, the total impedance is the speaker impedance divided by the number of speakers:
Parallel wiring is simple, and if one horn fails the others keep working. The drawback is that the load falls quickly, so most amplifiers run out of headroom after two or three horns per channel.
In series wiring, the amplifier's positive goes to the first horn's positive, that horn's negative goes to the next horn's positive, and so on; the last horn's negative returns to the amplifier's negative. Impedances add:
Series wiring is always safe for the amplifier, but the higher the load, the less power the amp delivers, so the horns get quieter. And if one horn opens up (fails), the whole chain goes silent.
Series-parallel combines the two to land back on a friendly load. The classic example is four 8-ohm horns: wire two pairs in series (16 ohms each), then connect the two pairs in parallel. The result is 8 ohms, the same as a single horn, while the amplifier's power is shared across four speakers. With eight horns you can build two of these groups and wire them in parallel for 4 ohms.
| Horns | Wiring | Total load |
|---|---|---|
| 1 | Direct | 8 Ω |
| 2 | Parallel | 4 Ω |
| 2 | Series | 16 Ω |
| 4 | Series-parallel | 8 Ω |
| 4 | Parallel | 2 Ω (only for 2-ohm-stable amps) |
| 8 | Two series-parallel groups in parallel | 4 Ω |
Use the same model of horn throughout a group. Mixing impedances or power ratings causes uneven volume and can push the weakest horn past its limit.
When horns share one amplifier channel, the power is split between them. If an amplifier delivers 200 watts into 8 ohms and you connect four horns series-parallel, each horn gets roughly 50 watts. That is often plenty: horns are efficient and voice paging rarely needs full power. But it means the horns' RMS rating should be at least the share each one receives, and you should set levels by ear starting low.
Always compare continuous (RMS) ratings, not "peak" or "max" numbers. Leaving 20–30% headroom keeps both the amplifier and the horns cool during long events.
Horns are often mounted far from the amplifier, on poles, rooflines or barn walls. Long runs of thin wire waste power as heat and can shift the load the amp sees. As a rule of thumb for 8-ohm loads:
Lower loads (4 ohms or 2 ohms) need heavier wire for the same distance. Our speaker wire gauge guide covers this in more detail. For outdoor runs, use cable rated for outdoor or direct-burial use where needed, and leave a drip loop below each horn so water runs off rather than into the terminals.
Connect every horn with the same polarity: positive to positive, negative to negative (or, in series, negative to the next positive). If one horn is reversed, it pushes when its neighbors pull. Where coverage overlaps, the sound partly cancels and voice becomes thin and hollow. Most speaker wire has a stripe or ridge on one conductor; pick one for positive and use it everywhere.
If you build your own horn from a throat and a separate compression driver, the same impedance rules apply, but the driver also needs a high-pass crossover so it never receives deep bass. Check the driver's recommended crossover point and mounting type. See choosing a PA horn and compression driver for a full walkthrough.
Products mentioned in this guide: the 6-inch all-weather PA horn, the larger 10-inch all-weather PA horn, and the paging horn throat for use with a separate compression driver.
Related guides: Choosing a PA horn and compression driver · Speaker wire gauge guide