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.

You can, of course, provide these limiter functions in a stand-alone loudspeaker processor (DSP), such as a Lake, BSS, Biamp, Ashly, or XTA product (to name a few). In this case, it is often advisable to run the amplifier levels “wide open” and manage gain in the DSP, so that nobody can come turn up the amplifiers later and cause problems.

Even with the excellent limiter options available in standalone DSP, though, I still like the idea of the limiters being in the last possible place in the signal chain (i.e., in the amplifiers). However, if you need a large quantity of amplifiers for your system, it can certainly be more cost-effective to let standalone DSP do the job and purchase amplifiers with no internal DSP.

Let’s come back to the idea of an “undersized” amplifier. Remember that it’s when the amplifier clips that causes problems, so the solution is simple: set limiters so that doesn’t happen. As long as you don’t clip the amplifier, there is absolutely nothing wrong with using an amp that is “too small.” You won’t get the maximum SPL potential out of the PA, but you may not need it, anyway. Many loudspeaker systems are capable of getting much louder than needed, so a little wasted potential may not be a big deal in the long run. Plus, loudspeakers tend to behave in a nonlinear fashion as you approach their limits anyway.

The takeaway should be that the amplifier size you choose is a function of balancing the maximum SPL you need out of the PA, with cost. The protection, whether the amplifier is oversized or undersized, comes from having both RMS and peak limiters to protect the loudspeakers (and prevent amplifier clipping in the case of an “undersized” amp).

Regardless of whether you do the limiting in the amps or in standalone DSP, do it somewhere!

I mentioned in the beginning that many modern amplifiers (usually those that have built-in DSP) can be networked for remote monitoring. I am a big fan of this function. Not only do you have the ability to monitor levels and limiter activity, you can also mute the system this way.

When doing a “burp” test (short bursts of pink noise done one amplifier channel at a time to test the loudspeakers), it is incredibly handy to be able to do this via a computer in the room with you.

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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