Navigating the power ratings jungle with clarity: Why RMS power reigns supreme as the load capacity rating for speakers
As a expert planner and installer, what should you be mindful of when comparing speaker load capacities to avoid being deceived by marketing tactics?
A new project is coming up. And you need to select the right PA system. Nowadays, speakers can have a range of load capacity ratings. You come across ratings like “music performance" or “RMS power" and “music power rating" or “RMS load capacity" and wonder what's behind it all. We spoke with Daniel Gradert, our sound quality expert. He outlines the key ratings to consider when searching for a new speaker for your project.
Load capacity or power – what is the right term?
The terms "load capacity" and "power" are colloquially used as synonyms. However, it is correct to speak of the load capacity of a speaker. A speaker's load capacity is the maximum power it can handle without sustaining damage. Load capacity ratings can be a helpful tool when purchasing a speaker. However, they are only a guideline that depends on where you want to use the speaker. A car door speaker operates under different conditions than a home sound system. Speaker ratings are greatly affected by environmental factors. That's why they are never 100% reliable.
Figuring out the power ratings of electronics is a piece of cake. With speakers it is a little more difficult because there are several components with different ratings. That's why there are several, sometimes outdated, methods for determining a speaker's load capacity:
- RMS load capacity: RMS stands for Root Mean Square. It describes the average power in the relevant frequency range that you can send to the speaker without causing any damage to it. The value refers to the continuous load and thus provides a good orientation for the real use of the speaker.
- Music performance: Music performance is the second load capacity rating used typically in addition to RMS. The speaker sometimes receives more and sometimes less power during the measurement (dynamic load). Then the measurement engineer checks how much power the speaker can withstand. So the value of load capacity ultimately refers to short-duration loads. It is therefore higher than the RMS load capacity, but does not provide reliable guidance for real application situations.
- Peak power: This measurement method is about what peak load a speaker can withstand, i.e. for a few milliseconds (impulse). The rating not only relates to the electrical load capacity of the speaker, but also to the overall mechanical load capacity. Today this value is hardly relevant anymore. It is more of a safety rating for extreme situations, for example in event technology.
Since the numbers used in music performance and peak power are higher than the RMS load capacity, they are sometimes used for marketing purposes. For example, a speaker with an RMS load capacity of 100 watts can have a music performance of approximately 200 watts and a peak power of up to 1,000 watts. The larger numbers are more appealing to inexperienced customers.
Higher = better? Or just marketing?
The load capacity as a single value has no influence on the sound quality of a speaker. So you should always consider all parameters together in context. However, some manufacturers still promote particularly high music load capacity or peak power. However, these values are unreliable: they are not measured under real conditions and therefore only represent the peak power at a certain point in time. You are comparing apples with oranges. However, some manufacturers or retailers still use the information to make their products appear more attractive.
Daniel Gradert | MONACOR INTERNATIONAL
“The bigger the number, the more likely a product is to sell. Still, the load capacity has nothing to do with the sound quality. There are speakers with 200 watts that are significantly higher in overall quality than those with 2,000 watts. You can't determine the quality of a speaker based on one rating."
Example:
In private living rooms (20-30 sqm), speakers with moderate power ratings are often sufficient. Because hardly any energy is lost there and the listener is in close proximity. This is not necessarily the case for large-scale or outdoor applications. The load capacity rating alone does not tell you how much the speaker can "do" – in other words, it does not tell you how much power the speaker can convert into sound energy (efficiency).
Find out more about interesting and helpful aspects of audio technology in our magazine
RMS load capacity is the best rating
If you want to make an informed decision, you should always take all of the manufacturer's parameters into account in your decision. For the load capacity, you can rely on standardised ratings such as the RMS power. RMS power is considered the official, international and only meaningful rating of the power of sound systems!
Daniel Gradert | MONACOR INTERNATIONAL
“Music performance can provide some initial orientation. The RMS load capacity is the more reliable value. Use these values as a compass for making decisions as a customer."
How to calculate RMS power
To determine the RMS value (in watts), experts measure the speaker's load across the entire relevant frequency range using so-called pink noise. Compared to white noise, pink noise is characterised by a level drop of 3 dB per octave upwards and is based on the average hearing perception of a person.
"Root Mean Square" is a statistical measure in electrical engineering...
... that describes the effective value of a variable signal. In the context of audio and PA technology, RMS is often used to quantify the "effective" power of an audio signal.
What does that mean in practice? Let's say you have an audio signal that constantly fluctuates. Some parts are loud (high amplitude), others are quiet (low amplitude). The RMS value gives you a sort of "average value" that represents the total energy of the signal. Compared to peak values, this method is effective in assessing the load capacity of amplifiers and speakers and providing a realistic view of their expected performance.
The RMS value is particularly important when it comes to avoiding distortion and overloading. A device designed for a specific RMS load capacity can withstand that level of "effective" power for an extended period of time without distortion or damage.
Conclusion: trust the experts
The load capacity of a speaker should always be viewed in its appropriate context. The area of application, the type of application or the frequency range used are important. As an expert planner or installer, you should always rely on standardised and reliable ratings. The RMS power rating is best suited for this purpose.
Headergraphic © AdobeStock | Irina
