HTHOLIC said:
explain that in non technical langauge- to play the system at 90db which can make a person go deaf- all 7 speakers, how much power would that use?
It seems like a simple question right? But there are a few unknowns here that can influence things a bit.
Anyway, here's a good start;
For every 3dB@1m of loudness you need to double the power output of the amp. So, for speakers with a sensitivity of 85db/1w/1m to play at 88dB@1m the amp would put out 2w. For 91dB@1m the amp would have to put out 4w, and 8w at 94dB@1m. It starts escalating pretty quickly from here to the point that the real sound level differences between a 150w and 500w amp become negligible. But there are then issues of headroom and the like but that’s a different subject.
Aha! I hear you say, but there's a but in here, so hang on a sec. The reason why you always see the "at 1 meter" stressed is that you lose dB's at a rate of knots for every extra meter from the speaker. I think, someone correct me if I'm wrong here, that for every doubling of the distance between yourself and the speaker you lose 6dB. To get 91dB@2m with speakers with a sensitivity of 85dB you'll need 16w because you lost 6dB with distance and had to add 6dB that required 2 doublings - 4Wx2 = 8Wx2 = 16W.
This is one of the reasons why people usually ask "how big the room is" with questions like this.
There's another but though, and that is you can get an increase in the dB's too depending on the room that you're in (that's what people refer to as "in room gain").
So, yes, your amp will probably be ok.
As for the "all 7 speakers". Normal music and HT doesn't drive all the speakers at the same levels at any point in time. Take a read of the "All channels driven fallacy" thread and article. It's cool.
