Live audio: Power requirements calculation: How?

[Amnesiac]

Im courious as to how do they come up with the equipment needs for big concerts.
A friend of mine told me the calculation used is based on quantity of attendants, 1 watt per person in the audience, but it sounds kind of vague to me.

What are the calculations used to figure out how much power is needed to properly deliver sound reinforcement to a big audience? (or a small audience for that matter)

Does it depend on venue size or on quantity of people in the audience?
Does it vary depending on the type of venue?(outdoors or indoors locations)

Please share any link or related reading, video, or published material around this topic you might have


Thank you!!

[Roland Clarke]

Originally Posted by Amnesiac

Im courious as to how do they come up with the equipment needs for big concerts.
A friend of mine told me the calculation used is based on quantity of attendants, 1 watt per person in the audience, but it sounds kind of vague to me.

What are the calculations used to figure out how much power is needed to properly deliver sound reinforcement to a big audience? (or a small audience for that matter)

Does it depend on venue size or on quantity of people in the audience?
Does it vary depending on the type of venue?(outdoors or indoors locations)

Please share any link or related reading, video, or published material around this topic you might have


Thank you!!

There is no "magic" answer to your question, there are a lot of variables. For a start I can tell you that 1 watt per person isn't going to do it. On this basis a pretty standard theatre of around 1,000 seats would be quoting a rig of 1k, that's a pretty standard bar gig system, equally it would only allow for a 5k system to cover 5,000 people!

You have to bear in mind that various system output (spl levels) will vary considerably for given input wattage. Also you have to take into acount coverage, often you will encounter situations where you will spec a larger system just to offer smooth coverage over a particular shaped area/room. On smaller or lower budget shows providers often supply equipment on the basis of what they know will do the job, larger shows will more often than not be calculated using array calculation software often supplied by the system manufacturer. Factor in that the system for a electronic pop band might need to be totally different than that for a jazz or rock band. A heavey metal band will expect to be much louder than a melodic vocal group leads to even more variety.

I've done outdoor shows with around 10-12k of D&B C4 (8 tops and 8 subs) with a pair of B2 subs and covered 5k audience, I've also seen 30-40k systems deployed in theatre's with an audience capacity of around 1100. For me, the best way to spec small systems is to consider the type of show, coverage required, and match your speakers SPL and coverage too that. I hope this helps as a guidline.

Regards


Roland