I believe that
RMS power is a misnomer, it has become commonly used but it really is a meaningless value and is actually the calculated
power based on
RMS voltage and
current measurements. Also realize that Program and Peak ratings are calculated rather than measured values, the
AES test signal used has a 6dB
crest factor, the peaks are 6dB above the average, so the "peak"
power is 6dB (4X) the continuous
power while "Program" is essentially a made up
rating to reflect that the test signal is not the same as a typical program source such as music and it is typically simply 3dB (2X) above the continuous
rating.
There are numerous different
speaker power rating schemes, some intended for individual drivers and some for full range devices.
AES ratings are quite common and you might see
IEC/
EIA ratings as well. A few manufacturers use their own proprietary hybrid or modifications of some of the standard test methods. Many of the differences relate to the driving signal applied (bandwidth, filter slopes,
crest factor,
etc.) and the time the signal is applied. There are pros and cons to each method. And do not think that marketing is not a factor in this, how many people really understand or even notice the differences in the test methods or specifics of the ratings versus those that simply look at the numbers? So if your competition changes the test methods used or how the information is reported then from a sales perspective there is definitely some pressure to do the same.
As the specs for
gaff's sub show, the length of test is a factor can also be a factor as longer test times can start to
reveal long term issues, typically thermal, when the
speaker is driven continuously for long periods. Not necessarily applicable for your 2 hour show with live music but perhaps relevant to the all night DJ with heavily compressed source material.
One of the limitations with
current power ratings is that a
speaker could have a noticeable change in response before reaching the rated
power and that would not be
identified. There are also a lot of calculated vlaues reported for both speakers and amplifiers. There is a move within
AES and by some of the independent
speaker testing labs to develop new
speaker and
amplifier rating systems that are based on the actual
voltage and
current measurements rather than calculated
power levels and that for speakers define the
power limit as when an audible (3dB) change occurs in the
frequency response. This makes a lot of sense to me as it means you are really looking at when the
power starts to affect what is heard and it is also a condition from which most speakers could recover.