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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => LAB Lounge => Topic started by: Steve Cochran on March 18, 2011, 03:34:56 AM
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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! :P 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.
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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 !!!
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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.
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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.
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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! :P 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/ (http://www.prosoundweb.com/article/we_need_more_power_captain_but_how_just_how_much_amplifier_power_is_needed/P1/)
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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! :P 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.
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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.
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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.
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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! :P 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
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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.
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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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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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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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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.
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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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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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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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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
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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...
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CalJam74 only had 54,000 watts of amp power and got out to over 200,000 people.
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CalJam74 only had 54,000 watts of amp power and got out to over 200,000 people.
And Woodstock had 10Kw of power and had over 500,000 people. I didn't say they all heard it great.
Cream used to tour with a 500 watt PA system NOT 500KW or 50KW, but 500 watts!
I remember reading that Grand Funk Railroad, back in their heyday was using a 7Kw per side PA.
That would barely make a decent side fill now-a -days.
Oh how systems change.
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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! :P 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.
Just half of your combined speaker wattage, half,
For a pair only consider one speaker, then half of it
(doesnt work for outside)
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Just half of your combined speaker wattage, half,
For a pair only consider one speaker, then half of it
(doesnt work for outside)
You MUST use your full real name on these forums to post or the thread will be locked
PS- your response does not make any sense to me-change your name and then try telling us what you mean-or maybe I don't understand you.
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Just half of your combined speaker wattage
Please go to your profile and change the "Name" field to your real first and last name as required by the posting rules displayed in the header at the top of the section, and in the Site Rules and Suggestions (http://forums.prosoundweb.com/index.php/board,36.0.html) in the Forum Announcements section, and on the registration page when you registered.
Mac
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***ALERT***
ZOMBIFIED THREAD
***ALERT***
What on earth are y'all talking about?
Come up with some definitions before engaging in conversation otherwise everyone is running around with massive ASSumptions trying to answer vague questions.
-Acoustical "watts" eg. energy in the air?
-Amplifier "watts" eg. how many watts the amps can output? (if so what kind? average, continuous, peak, instantaneous?)
-Speaker "watts" eg. how many watts the speakers can handle without blowing up? (if so what kind? average, continuous, peak, instantaneous?)
-Power "watts" eg. how many watts of AC (from the power company) is being drawn (if so what kind? average, continuous, peak, instantaneous, power factor?)
-head "watts" eg. how much the human head leaks into its environment? (if so, what is the ambient temperature, humidity, size of head, coverings, etc... BTU's?)
As it stands, I have no idea what anyone is talking about.
If I'm assuming the question is how many amplifier watts is needed per typical head in a venue of densely packed persons then that can only be answered after this process:
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
Reason being is speakers sensitivity (and power handling) will dictate the amplifier wattage WAY more than number of persons (though they are intricately entwined) and area will dictate the type of speaker coverage needed (# of speakers &/or type) way more than directly influencing the amplifier's wattage.
I can't believe anyone hasn't stated this simple answer already...?
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What on earth are y'all talking about?
Come up with some definitions before engaging in conversation otherwise everyone is running around with massive ASSumptions trying to answer vague questions.
-Acoustical "watts" eg. energy in the air?
-Amplifier "watts" eg. how many watts the amps can output? (if so what kind? average, continuous, peak, instantaneous?)
-Speaker "watts" eg. how many watts the speakers can handle without blowing up? (if so what kind? average, continuous, peak, instantaneous?)
-Power "watts" eg. how many watts of AC (from the power company) is being drawn (if so what kind? average, continuous, peak, instantaneous, power factor?)
-head "watts" eg. how much the human head leaks into its environment? (if so, what is the ambient temperature, humidity, size of head, coverings, etc... BTU's?)
As it stands, I have no idea what anyone is talking about.
If I'm assuming the question is how many amplifier watts is needed per typical head in a venue of densely packed persons then that can only be answered after this process:
Reason being is speakers sensitivity (and power handling) will dictate the amplifier wattage WAY more than number of persons (though they are intricately entwined) and area will dictate the type of speaker coverage needed (# of speakers &/or type) way more than directly influencing the amplifier's wattage.
I can't believe anyone hasn't stated this simple answer already...?
ZOMBIES!!!! (psst - this thread is 6 years old)
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ZOMBIES!!!! (psst - this thread is 6 years old)
Ughh, I hate it when the new guys dig up an old thread by commenting on it and it pops to the top of my feed! I didn't notice the original time!
Thanks Tom (or TJ?)!
Also, can I blame Ivan for responding first? :P
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Ughh, I hate it when the new guys dig up an old thread by commenting on it and it pops to the top of my feed! I didn't notice the original time!
Thanks Tom (or TJ?)!
Also, can I blame Ivan for responding first? :P
TJ is fine, and it's totally ok with me to blame Ivan. :)
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What on earth are y'all talking about?
Come up with some definitions before engaging in conversation otherwise everyone is running around with massive ASSumptions trying to answer vague questions.
-Acoustical "watts" eg. energy in the air?
-Amplifier "watts" eg. how many watts the amps can output? (if so what kind? average, continuous, peak, instantaneous?)
-Speaker "watts" eg. how many watts the speakers can handle without blowing up? (if so what kind? average, continuous, peak, instantaneous?)
-Power "watts" eg. how many watts of AC (from the power company) is being drawn (if so what kind? average, continuous, peak, instantaneous, power factor?)
-head "watts" eg. how much the human head leaks into its environment? (if so, what is the ambient temperature, humidity, size of head, coverings, etc... BTU's?)
As it stands, I have no idea what anyone is talking about.
If I'm assuming the question is how many amplifier watts is needed per typical head in a venue of densely packed persons then that can only be answered after this process:
Reason being is speakers sensitivity (and power handling) will dictate the amplifier wattage WAY more than number of persons (though they are intricately entwined) and area will dictate the type of speaker coverage needed (# of speakers &/or type) way more than directly influencing the amplifier's wattage.
I can't believe anyone hasn't stated this simple answer already...?
This thread is form 2011, Nathan. Let sleeping zombies lie...
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TJ is fine, and it's totally ok with me to blame Ivan. :)
That's fine. I get blamed for all sorts of things.
Sometimes it is good :)
Other times-we won't talk about that
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Well I didnt dig it up and that means my GF will not spank me for doing a bad thing. bummer !
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Well I didnt dig it up and that means my GF will not spank me for doing a bad thing. bummer !
What the heck?!?
Award for non-related post of the year, I think... =-\
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The result of applying electrical watts to a transducer (and its horn/cabinet and mounting/installation) is completely dependent on the transducer's ability to produce acoustic watts where you want it.
This explanation should help.... ;D
"Sound Power Density : is the Sound Energy Flux in a specified direction and sense through an area perpendicular to that direction, divided by the area."
http://www.acoustic-glossary.co.uk/sound-power.htm
It has been said that it is your job is to fill an area (which may be enclosed by a container) with sound. The people are just there to listen (and maybe help dampen some reflections).
-Dennis
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Watts that noise in my head Doc ? Give it to me straight Doc ! Am I dunn ?
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Watts that noise in my head Doc ? Give it to me straight Doc ! Am I dunn ?
If you're deaf, you're Brooks...
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Did you know the average horse produces about 11 horsepower.
Sent from my XT1254 using Tapatalk
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Did you know the average horse produces about 11 horsepower.
Sent from my XT1254 using Tapatalk
That would be the "peak" horse power.
They "can" do it, but not for long.
They cannot sustain that level. The "average" horse power is equal to 1 horse.
Here we go again----------------------
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Did you know the average horse produces about 11 horsepower.
Sent from my XT1254 using Tapatalk
So a horse can go to 11 just like an amp therefore an amp that goes to 11 produces 11 horsepower
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If you're deaf, you're Brooks...
Dunn !