Over the years in the audio industry, I have made numerous attempts to explain some of the concepts used with regard to speaker/amplifier power. Most are summarised below, with links to some of the articles covering each topic in more detail. If you’re serious about sound, and curious about power, these are well worth a read, and will help you make more sense of power.
What is Power (Watts)?
Power is a measure of how fast energy is being used or delivered. One watt is defined as one joule per second, which in audio terms is the rate at which energy is transferred from an amplifier to a loudspeaker. High power for a short burst and lower power delivered continuously can result in the same total energy, which is why power must be considered over time.
For example, a 4 W burst for 0.25 seconds followed by 0.75 seconds of silence delivers the same energy as a 2 W burst for 0.5 seconds followed by 0.5 seconds of silence, or 1 W delivered continuously for 1 second.
This simplified example is an analogy for understanding peak, program, and continuous power. Peak power represents short, high-energy bursts, program power represents longer bursts with more time at a high level, and continuous power represents energy delivered without breaks. Although real music does not follow fixed duty cycles, all three cases above average to the same energy rate: 4 W × 0.25 = 1, 2 W × 0.5 = 1, and 1 W × 1 = 1.
This is why loudspeaker power ratings typically follow the same pattern: program power is usually twice the continuous rating, and peak power is typically four times the continuous rating. The numbers relate to the same underlying energy, but describe how that power is delivered over time.
RMS Power
RMS is a mathematical method that works extremely well for steady sine waves, such as AC mains power, where voltage and current are continuous and predictable. Music is not like this, so “RMS power” is not ideal for describing real audio behaviour. Some amplifier manufacturers still use the term, but it often includes a hidden crest factor or burst condition, meaning the figure is not a true continuous power level but a calculated equivalent.
Read more…
AES / Continuous Power
AES power defines how much power a loudspeaker can handle on average over time using a standardised broadband noise signal. It represents the long-term thermal limit of the voice coil and is the most reliable figure for continuous operation. Unlike RMS-style ratings, AES power is designed specifically for real audio signals rather than steady test tones.
Program (Music) Power
Program power allows for higher short-term peaks while keeping the long-term average power the same as the AES rating. It reflects the dynamic nature of music, where loud transients are followed by quieter moments. Program power is headroom, not extra continuous power, and should never be treated as a sustained operating level.
Read More on AES / Program Power
How much Power do you need?
What’s up with the Watts?
Power ratings in audio can be confusing because music is dynamic, not constant. Its hard to know what you want, what’s best and how to use power figures sensibly when choosing speakers and amplifiers.
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Pe – Power Handling Capacity
Often seen in manufacturers technical data, Pe is the long term power handling capacity, usually measured using the AES standard (but not always) and some manufacturers have their own test criteria and will often name this ‘nominal power handling’ This is not necessarily comparable between all speaker brands – also a little explanation as to why MORE POWER does not necessarily mean MORE VOLUME
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