Power Ratings are specifications on passive speakers. They help you determine which amplifier you need. Program (PGM) is the wattage level where the speaker is most efficient. It represents a realistic scenario in which input level rises and falls, giving the speaker time to rest.
Continuous, sometimes referred to as RMS (Root Means Square) represents what the speaker can handle when the same amount of power is applied continuously without rest. This is a more conservative rating and one that should be considered if you will be playing loud music without breaks, for long periods of time. Having a continuous signal pumping constant energy into the speaker results in heat. If the signal doesn’t wean, and you are surpassing the Continuous rating, eventually the voice coil in the speaker will melt.
One of the misleading power ratings is Peak. Peak represents the absolute maximum power a speaker can handle for a fraction of a second. Feeding the speaker constant peak wattage will result in damage.
When matching speakers and amps, pick an amplifier that has at least 20% more power than Program, and at least 10% less power than Peak. If the speaker has a Program rating of 500 watts, and a Peak rating of 1000 watts, the amplifier should be somewhere between 600 to 900 watts.
When the amplifier provides more power than the speaker’s Program rating, the speaker will perform at optimum efficiency with plenty of headroom without overworking the amp. The term headroom refers to the difference from the speaker’s normal level of operation and the point in which the speaker begins to distort. Just don’t turn the amplifier up all the way or the speaker will eventually blow.
Believe it or not, most people damage speakers due to under-powering them. This is because cranking an underpowered amp all the way up can send raw power spikes that the speaker can’t handle. In addition, the amp will be working harder to give the speaker sufficient power, causing it to run hot which can damage the amp.