as i now have the time, let me give an example.

a few days ago i played the movie Super 8 at Reference Level; once it was over, i checked the Watt meter to which the FR and FL speakers are connected to the house current, through one QSC amp.
it said Max Watts = 1278 Watts. that's a total for 2 speakers.
for one speaker, we divide the number by 2 = 640 Watts/ch.

the amp efficiency is around 70%, so i multiply 640 Watts by 0.7 which gives around 448 effective Watts for one speaker.

now, the sensitivity for the M80 is 95 dBSPL/Watt/meter, in room.
as i sit at a distance of about 2 meters, then i get around 91 dBSPL/Watt/2 meters. The loss for doubling the distance is 6 db, but that's for open spaces; in my room, it's more like a 4 dB loss.

going from one Watt to 448 Watts is an increase of around 26 dB;
so, 91 + 26 = a SPL of 117 dB for one speaker.
the total output for the 2 front speakers is doubled, to 120 dBSPL, at 2 meters (MLP).

then, my SPL meter said that the loudest peak registered was 122.3 dB/flat scale.
I think the difference between 120 Db and 122.3 dB comes from the fact that the subs have to be taken into account as well as also the 4 surround speakers.

this is all approximate, but should be quite near the real numbers.
true peak power indicators are too costly for my needs.

if my method is wrong or does not make sense, please tell me how, i would be grateful for that.

Edited by J. B. (09/05/12 12:32 PM)
or: Axiom Gallery