Amplifiers: To Protect Speakers, Account For Peak Power, RMS

Whenever possible, look to follow the manufacturer’s recommendation to yield the best results and minimize the likelihood of damage to your loudspeakers.

Amplifiers: To Protect Speakers, Account For Peak Power, RMS
Ideally, you would purchase amplifiers that the loudspeaker company endorses and use the presets already configured within the amplifier.

The other major function that many modern amplifiers have is an ongoing load test, which continually monitors the connected loudspeakers. By comparing the reported load (e.g., 1.7 ohms) to the expected load (perhaps 4 ohms for a pair of 8 ohm speakers in parallel), you can see that something is wrong. Perhaps the loudspeaker cable is developing a short, or a voice coil is melting). This load test doesn’t usually conclusively prove what is wrong, but it will often give you an idea of what to investigate. And with the complexity of modern PA’s, any “health” data we can get is helpful.

In a nutshell, keep the following points in mind:

• Whenever possible, consult the loudspeaker manufacturer and use their recommended amplifier pairing suggestions and presets.

• Use both RMS and peak limiting to fully protect your loudspeakers.

• Don’t be afraid to use a smaller amp than your loudspeaker can handle, if you don’t need the SPL, and you use limiting to prevent the amplifier from clipping.

• Otherwise, pick an amplifier that delivers around two to four times the continuous power rating of the loudspeaker.

• Do your loudspeaker tuning either in a standalone DSP or in the amplifier’s DSP (if available), but please don’t do it in your console. Console-based PA tuning is susceptible to accidental fiddling by others and means that swapping out your console will also result in you losing your system tuning.

• Generally, don’t be tempted to load an amplifier channel lower than 4 ohms, even for amplifiers that can handle it. It typically requires larger loudspeaker cable, both because of the higher current involved and to overcome cable loss, and it can also make some amplifiers nonlinear.

And finally, if you need help making the choice, or determining limiter settings, do not be afraid to reach out to a preferred integrator, a consultant, or (maybe) the wonderful online community. If you pick the latter, though, just be prepared to judiciously exercise your comprehension skills!


More About Brad Duryea
Brad Duryea is an audio engineer based in Houston, Texas, where he is the director of audio technology for Lakewood Church. He can be reached at or via Twitter: @bradduryea.
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