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[Steve Cochran]

Hey all!  I've been referencing these forums for a long time, and this is the first time I haven't found my question had already been asked and answered!

My question is, I read somewhere some years ago a "watt per head" rule.  I'm pretty sure it was just one of those "rule-of-thumb" things, but for the life of me, I can't remember what the figure was. 

I'm fairly confident I know what it takes to accomplish gigs that come my way.  I tend to overkill a little anyway!     I just wanted to see if any of the experts in here know the rule and where it may have come from.

Thanks in advance for your time and thoughts.

[Jeff Bankston]

since i never heard that the only thing i can think of is amp wattage vs speaker handling wattage. its always ben a good thing to have an amp with a tad more RMS/AES power then the speaker is rated at. i use a 1100 watt into 4 ohm load amp to power a pair of 8 ohm speakers wired parallel each having a RMS/AES power rating of 500 watts. so that 1100 watts amp power and 1000 watts speaker handling power. that way if every so often you see the clip light barely flicker your not trying to overdrive an underpowered amp into clipping and burning up a speaker that can handle more power than the amp can make. you will also get the maximum spl from the amp/speaker combo. i dont know if this is "watt" you "mint" but its a great rule of thumb. an amp is also called a head. a toilet is also called a head but i dont think we can use it to power the speakers with !!!

[Steve Cochran]

since i never heard that the only thing i can think of is amp wattage vs speaker handling wattage. its always ben a good thing to have an amp with a tad more RMS/AES power then the speaker is rated at. i use a 1100 watt into 4 ohm load amp to power a pair of 8 ohm speakers wired parallel each having a RMS/AES power rating of 500 watts. so that 1100 watts amp power and 1000 watts speaker handling power. that way it your pudhing the amp and every so often you see the clip indicater barely flicker your not trying to overdrive an underpowered amp into clipping and burning up a speaker that can handle more power. your also getting the maximum spl from the amp speaker combo. i dont know if this is watt you mint but its a great rule of thumb. an amp is also called a head. a toilet is also called a head but i dont think we can use it to power the speakers with !!!

Thank you for your reply, but that isn't the info I'm after.  I know how to power boxes. 

No, the rule I'm talking about is in terms of system size vs crowd size.  If I remember correctly, indoors it was 4 watts/person, outdoors was 11 watts/person...but that is a guess.  It is just supposed to be a general guidline to help properly power the event, and aid in bidding.  Additionally, I would think that it varys by overall music genre for the given event as well.

[Jeff Bankston]

thats a very complex subject. you have to take into account the room size,wall,floor,celing, material. how high up the speakers are. what spl do you want at say 15 feet and 50 feet ? what is the maximum number of people that will be there ? is it a heavy metal band that wants to be real loud or a square dance band that just wants to be heard ? i'm sure you know all this but i looked a many a time on the web and came up with what i already knew. with an outdoor gig if theres no wind or the wind blows toward the audience thats great if toward the band its bad. some of the rock concerts i went to at the jackson mississippi colusium back in the 70's didnt have a big enough pa for the 10,000 people capacity. if you were halfway back it wasnt loud and if were all the way back it was a joke. it would be great if there were a magic formula to use when playing an unfamiliar size/type room. CALJAM 74 had about 5 watts per person.

[luis Markson]

Hey all!  I've been referencing these forums for a long time, and this is the first time I haven't found my question had already been asked and answered!

My question is, I read somewhere some years ago a "watt per head" rule.  I'm pretty sure it was just one of those "rule-of-thumb" things, but for the life of me, I can't remember what the figure was. 

I'm fairly confident I know what it takes to accomplish gigs that come my way.  I tend to overkill a little anyway!     I just wanted to see if any of the experts in here know the rule and where it may have come from.

Thanks in advance for your time and thoughts.

I havn't read this yet , but it seems it will answer both our questions...
http://www.prosoundweb.com/article/we_need_more_power_captain_but_how_just_how_much_amplifier_power_is_needed/P1/

[Brad Weber]

Hey all!  I've been referencing these forums for a long time, and this is the first time I haven't found my question had already been asked and answered!

My question is, I read somewhere some years ago a "watt per head" rule.  I'm pretty sure it was just one of those "rule-of-thumb" things, but for the life of me, I can't remember what the figure was. 

I'm fairly confident I know what it takes to accomplish gigs that come my way.  I tend to overkill a little anyway!     I just wanted to see if any of the experts in here know the rule and where it may have come from.

This question has actually been answered many times and the answer is that it simply doesn't work that way.  Even for the same event, differences between the speakers and/or the speaker system configurations employed could introduce a factor of 4 of more for the power required to obtain the same result.  Put simply, due to variations in the desired results, system configurations, audience area layouts and speaker sensitivities, there is no direct general relationship between the audience size and the amplifier power required, you have to look at the specific situation. 

[Ivan Beaver]

This question has actually been answered many times and the answer is that it simply doesn't work that way.  Even for the same event, differences between the speakers and/or the speaker system configurations employed could introduce a factor of 4 of more for the power required to obtain the same result.  Put simply, due to variations in the desired results, system configurations, audience area layouts and speaker sensitivities, there is no direct general relationship between the audience size and the amplifier power required, you have to look at the specific situation.

And to make it even more complicated, if there were such a "rule" it would have to be a sliding scale.  For smaller crowds, you would need more "wattage per head" than at larger gigs-to get the same SPL's.

BUt if somebody really has to have a number-it should be in the range between 1 and 100 watts/head.  That should give a good starting point.

[Robert Weston]

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. 

[Chris Carpenter]

Hey all!  I've been referencing these forums for a long time, and this is the first time I haven't found my question had already been asked and answered!

My question is, I read somewhere some years ago a "watt per head" rule.  I'm pretty sure it was just one of those "rule-of-thumb" things, but for the life of me, I can't remember what the figure was. 

I'm fairly confident I know what it takes to accomplish gigs that come my way.  I tend to overkill a little anyway!     I just wanted to see if any of the experts in here know the rule and where it may have come from.

Thanks in advance for your time and thoughts.

I recall reading an article like that a bit back as well. If I remember correctly, it estimated 5 watts per head for vocals, and 10-15 watts per head for music. But I think the calculation was supposed to be mostly for kicks. You would never definitively calculate your output power based on that one variable alone. Additionally, sensitivities vary among speakers, so a decent amount of power on one rig may not be enough for another rig for the same amount of people. I think the idea of the per head thing was to get you thinking about how power scales. If your alone in your bedroom, 15 watts is plenty. If You've got 9 more people in the room watching a movie, you need around 150 watts. If you are working with a stage with 100, you need at least a thousand... etc

[boburtz]

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.

[ProSoundWeb Community]