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Things To Consider When Buying Passive PA Speakers

Power Rating - Continuous (RMS), Program and Peak

PA Speaker power ratings are most often listed values for Continuous (also often called RMS), Program (sometimes called Music) and Peak power. But what do these mean?

Continuous power refers to a worst case scenario where you are blasting the speaker with sound at all frequencies (pink noise to be specific) for hours and hours on end. The biggest problem with speakers tends to be overheating and this doesn't allow the speaker to take a break and cool down. Unless you are an avant garde pink noise outfit with pieces lasting hours your actual music won't stress the speakers this hard.

Manufacturers also list Program or Music Power which is just about always double the Continuous Power rating. This is the rating for some version of 'typical' music power loads where there is dynamic range and periods of relative quiet which allows the speakers to cool down.

Peak power refers to how much your speakers can produce for an 'instant' which can both cause a lot of heat and is the limit to which the diaphragm of the speaker can safely move. The Peak power listed is nearly always double the music power and four times the Continuous Power.

Matching with Amplifier Power Ratings

You'd think that matching up the Continuous RMS Power with the output power of your amp would be safest and best bet but it turns out that many recommend a more powerful amp than this rating. A typical recommendation is about double this level which as we've learned above is generally Program or Music Power. So if you have a passive speaker that has a continuous power rating of 500W, the optimal amplifier to use is one rated 1000W or close to that. The reasoning is that apart from getting the most out of your speakers for typical loads, you are less likely to turn you amp up too high which can lead to a clipped/distorted signal rather like a square wave. A clipped signal from you power amp is the worst kind of signal for your speaker and can damage them even at lower power levels. There are even those who recommend an amp that goes all the way up to the Peak Power. On the other hand some recommend that matching to Continuous RMS Power is the safest bet. From our research the main point is to make sure your power amplifier doesn't go into the red whatever the power rating and that using around double the Continuous RMS rating is appropriate for normal music loads.

Impedance Matching

The typical load for speakers are 4, 6 or 8 ohms (Ω). The safest route is to have an amplifier that matches the load (4 ohm amp output to 4 ohm speaker). Low impedance speakers cause amplifiers with high impedance outputs to work harder, which result in audio clipping or worse - faster heat build up that may damage your equipment. So pairing your speaker impedance properly is important to preserve your amplifier and speaker, and to have a clear sound.

Speaker Loudness and Sound Pressure Level (SPL)

The wattage ratings of PA speakers relate to how much power they use up and this doesn't always relate directly to how much sound they can produce. This is because speakers vary in their efficiency at producing sound vs heat. The speaker efficiency rating is called Sensitivity which is how loud in decibels (db) it will be 1 meter from the speakers with 1 watt of power. The overall maximum loudness of the speakers is the Maximum SPL which is also measured at 1 meter in front of the speaker. While this can be a useful comparison point, it's important to point out that this doesn't give you a consistent measure of what levels of clarity and precision there are at these high levels so apart from cranking the speakers and listening from a safe distance, the best method is to check what others have experienced using the speakers in real life situations. Fortunately for you this is what we've done and incorporated into our written analysis.

Speaker Cone Size

Most of the top rated passive speakers have either 12" or 15" woofers with these two speaker sizes considered the most ideal for music PA systems. The general difference is that bigger 15" speakers offer more punch and low end (although not as much as a subwoofer), at the cost of overwhelming some of the highs. They also tend to be more expensive and heavier. 12" speakers offer a more balanced sound for many applications, but may not be enough for bass-heavy music. Also worth considering is the size of the tweeter, the presence of a midrange woofer, and the type of material used for the cone and tweeter.

Weight, Portability and Mounting

Since there are no built-in amplifiers inside the cabinet, passive speakers are expected to be lighter. This makes them ideal for mobile productions that move from place to place. Other portability friendly features to watch out for include stand/hang compatibility, handle location, size, and of course the actual weight.

Passive PA Speaker Summary

If you feel there is a speaker which should be included above, first check to see if it's in our Music Gear Database, then let us know in the comments below if you would like us to consider including it.