"AES power" is based on a standard issued by the Audio Engineering Society for characterizing various parameters of speaker drivers, including power handling capability. Here is a link to the first few pages of the standard (there is a charge for non-members to obtain the full document):
http://www.aes.org/tmpFiles/aessc/20181207/aes02-2012-i.pdf
Also, the following statement appears at https://www.dasaudio.com/en/f-a-q/power-handling/what-is-aes-power/
Kijanki is of course correct that strictly speaking average power and RMS power are two different things, although the term RMS power is widely (mis)used to refer to average power.
Regards,
-- Al
http://www.aes.org/tmpFiles/aessc/20181207/aes02-2012-i.pdf
Also, the following statement appears at https://www.dasaudio.com/en/f-a-q/power-handling/what-is-aes-power/
The AES (Audio Engineering Society) publishes a standard for the measurement of loudspeaker component parameters. Generally speaking, this standard calls for a 2-hour test using pink noise with specified dynamics and with a frequency content that matches the component`s frequency range. Although it is a standard for components, it is often extended to the different ways on an active system. The rating always derives from RMS voltage or current measurements, therefore the rating corresponds to average (“RMS”) power.
Kijanki is of course correct that strictly speaking average power and RMS power are two different things, although the term RMS power is widely (mis)used to refer to average power.
Regards,
-- Al