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Author Topic: Watts per head?  (Read 25774 times)

James Feenstra

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Re: Watts per head?
« Reply #10 on: March 18, 2011, 02:54:10 pm »

For what it's worth...

Not sure if this is what you are referencing... Many years ago (mid 80's?), I came across something that gave an average amount of watts per square foot (not per head).  It was pretty basic, and all being very relative and subjective (as referenced in the above posts in this thread), it went something like this:

Vocal only for indoors = 10 watts/sq. ft.
Music indoors = 20 watts/sq.ft

Vocal only for outdoor = 30 watts/sq. ft.
-- Don't recall anything for outdoor music

For example:  15000 sq. ft hall x .1 (10 watts) = 1500 watts for vocal projection only.

Personally, I don't "prescribe" to these calculations.
10w/sq ft in that scenario is 150,000 watts, not 1500w...which would be massive overkill in today's world for high efficiency loudspeakers...that's about the size of your typical arena Pa system in a 150'x100' room
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Andre Vare

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Re: Watts per head?
« Reply #11 on: March 18, 2011, 02:56:18 pm »

Another significant factor is if line array systems are used for coverage in their effective range.  Half the level reduction per distance doubling.

There are way too many other factors involved for there to be a simplistic equation.

Andre
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Robert Weston

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Re: Watts per head?
« Reply #12 on: March 18, 2011, 03:03:47 pm »

10w/sq ft in that scenario is 150,000 watts, not 1500w...which would be massive overkill in today's world for high efficiency loudspeakers...that's about the size of your typical arena Pa system in a 150'x100' room

The watts was probably more of guide, but yes 10 watts/sq. ft. is a lot. 

Though, if you interpret the 10 watts as .1  you get the 1500 watts.
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Jeff Bankston

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Re: Watts per head?
« Reply #13 on: March 18, 2011, 03:05:19 pm »

based on experienced i say bring a little more then you think you need. you can always keep the level turned down but if your running wide open and it aint loud enough your screwed.
« Last Edit: March 18, 2011, 03:08:07 pm by Jeff Harrell »
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Glen Kelley

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Re: Watts per head?
« Reply #14 on: March 18, 2011, 03:57:32 pm »

I have seen a "watts per head" spec listed in a few technical riders. This would have been in the late '90's, and seemed to be most prevalent with CCM and Country music acts. Perhaps a tour manager read the same paper you saw and decided it sounded nice.....

I don't believe this figure correlated in any way to the actual requirements of these gigs, or what was actually provided.  ;D
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Tim McCulloch

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Re: Watts per head?
« Reply #15 on: March 18, 2011, 04:15:11 pm »

A better formula for determining equipment needs for a particular event would be to ascertain the size and shape of the space you want to fill with sound, figure your spl requirements, then calculate your system needs based on amplifier power, your speaker sensitivity, and directionality.

This would be the correct answer.  It will be ignored or denigrated because it's not easy, fast, and requires mathematics beyond the 4 basic functions.
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Mike Reilly

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Re: Watts per head?
« Reply #16 on: March 27, 2011, 10:53:43 am »

I have seen a "watts per head" spec listed in a few technical riders. This would have been in the late '90's, and seemed to be most prevalent with CCM and Country music acts. Perhaps a tour manager read the same paper you saw and decided it sounded nice.....

I don't believe this figure correlated in any way to the actual requirements of these gigs, or what was actually provided.  ;D

Yup - working house tech for various smallish rock clubs in the 90's I saw "10 watts per person minimum" in quite a few riders.

God knows where it originated, and I strongly suspect most TM's, BE's or bands never even knew it was in the rider.  If they did, I bet they kept it in there only so they'd have some ammunition in case they were provided with a REALLY inadequate PA.
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Patrick Tracy

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Re: Watts per head?
« Reply #17 on: March 27, 2011, 12:25:21 pm »

A better formula for determining equipment needs for a particular event would be to ascertain the size and shape of the space you want to fill with sound, figure your spl requirements, then calculate your system needs based on amplifier power, your speaker sensitivity, and directionality.

My version of this:

1. Determine SPL and coverage requirements
2. Select a speaker system that meets those requirements with headroom to spare
3. Select amplifiers that will drive the speakers to the required SPL with headroom to spare

James Feenstra

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Re: Watts per head?
« Reply #18 on: March 27, 2011, 01:43:10 pm »

The watts was probably more of guide, but yes 10 watts/sq. ft. is a lot. 

Though, if you interpret the 10 watts as .1  you get the 1500 watts.
1500KW maybe (even though still incorrect mathematically, 10w as KW would be 0.01kw not 0.1kw, still concluding to 150,000w or 150kw, as it's 10/1000 not 10/100 to go from W to KW)

in no laws of mathematics is 10 of something ever equal to 0.1 of the same thing

using pie as an example;

Sally's diet allows for her to eat 0.1 of a pie every day. Sally eats amounts proportional to the above provided formula (10 = 0.1) and wonders why she's 450lbs and spends $80 on pie every day.

please explain how 10w = 0.1w, show your work and use examples, because everything I've learned in several years of physics, electrical theory and mathematics points to an opposite answer...

1500w is like a jbl Eon 10" and a powered 15" sub, one top and one sub per side (provided we're going continuous rating, not peak...if peak you only get 1/2 the PA)....anyone who brings that to do a 15,000 sq/ft room should be fired...
« Last Edit: March 27, 2011, 02:03:07 pm by James Feenstra »
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Jeff Bankston

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Re: Watts per head?
« Reply #19 on: March 27, 2011, 06:53:07 pm »

CalJam74 only had 54,000 watts of amp power and got out to over 200,000 people.
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Re: Watts per head?
« Reply #19 on: March 27, 2011, 06:53:07 pm »


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