Here's a new video explaining how to work out how much power you need for your speakers. Note that, in order to make the methodology universally applicable, the speaker makes reference to a system playing in an anechoic enviroment. In the end he explains what happens when you put it in a room.
Here is the vid: https://www.youtube.com/watch?v=qBuHmThA-7o
FYI, 85dB(A) is the sound level above which industrial laws consider sound level to be potentially harmful to hearing if sustained. Some examples here: https://www.chem.purdue.edu/chemsafety/Training/PPETrain/dblevels.htm.
Here is the vid: https://www.youtube.com/watch?v=qBuHmThA-7o
FYI, 85dB(A) is the sound level above which industrial laws consider sound level to be potentially harmful to hearing if sustained. Some examples here: https://www.chem.purdue.edu/chemsafety/Training/PPETrain/dblevels.htm.