There are… probably too many ways to communicate audio power ratings. Some are better than others. Let’s make like an old car and break it down:
RMS: a trusted, respected and widely used power handling specification. RMS is short for “Root mean square”. The true definition is too technical for this article, but it basically means the amount of power a speaker can handle, or an amplifier can produce, over an extended period of time without failing. We’re generally talking about tests that last for like.. 100 hours or so. When shopping for audio equipment, you should really be looking for the RMS rating above any other power rating.
Continuous: umm… basically RMS. This article is meant for the average joe, but I just know some professor Frink wannabe is going to email me with “well akshually, the sine wave with the glayvin is abstracted from the hypotenuse of the… ” You know what? Actually, this article ain’t for you!
AES: short for Audio Engineering Society. It’s similar to RMS, but uses different measurements. RMS is about 8/10 of AES. for example, 80w RMS = 100w AES – more or less.
Max power/Peak power basically means the maximum amount of wattage that is produced or can be handled in short bursts. This is usually double the RMS.
Program/Music power: usually this means the same as max or peak, but different manufacturers may define it differently.
Nominal power: better ask the manufacturer, this one is too slippery to define.
PMPO: a full-on garbage rating. Marketing sleaze turned up to 11. It stands for “Peak Momentary Power Output”. Basically means that if an amp can produce a spike for any measurable amount of time, it can be said to produce that many watts PMPO. If you see PMPO used to define the power rating on a piece of audio equipment, you will probably be very disappointed in that piece of audio equipment.