How many watts per person?

[skunky_funk]

In the past I knew that a rough way to estimate the power you need for your PA is a certain number of watts per person. Say you wanna design a PA for a bar with a seating capacity of 500, how much wattage do you need?

[ratthedd]

I'm sure that question deserves a whole bunch of "That depends..." answers.

 

Carvin used to include "number of people coverage" claims in their catalogs which amounted to roughly 1 watt per person in a fairly efficient full range system.

 

Here come the "That depends..."

 

...if you are running subs.

...if the bar is an oddball shape,

...if the bar is an echo chamber,

...on the efficiency of your speakers,

...on your on-stage volume levels,

...on the type of music you play,

 

 

I would venture to guess that a good rul of thumb for a decent full range system (not bi-amp or tri-amp) would be around 1.5 watts per person.

 

A better rule of thumb would include the cubic footage of the area you're trying to cover for indoor gigs, and square footage for outdoor gigs (appropriately adjusted, of course.)

 

Erik.

[Axisplayer]

 

Originally posted by ratthedd I would venture to guess that a good rul of thumb for a decent full range system (not bi-amp or tri-amp) would be around 1.5 watts per person.

 

 

You mean you really think that 500 people could be covered with 750 watts????

 

I want some of what you are on! I think you would be closer if you took out your decimal point and made it 15 watts.

 

My little system has 1850 watts on subs and 1700 on tops, and it handles about 250-300 people rather well. Thats about 3500 watts for 250 people. But much will depend on desired SPL, music type, room, etc. as you mentioned. Even just talking full range single cabs, I think you need at least 8-10 watts per person to hit rock volumes.

 

I think 1 watt per person is an almost laughable proposition.

[ATOMICDOG1]

The general rule of thumb that I generally go by for rock shows indoors, is 10w/person. So, for 500 people thats 5000 watts. Outside I generally like to have about double what I do indoors.

[agedhorse]

Just the efficiency issue really makes a rule of thumb hard to generalize.

 

For example a system with 10 watts per person at an efficiency of 95dB/1W/1M could be replaced with 2.5 watts/person if the efficiency were raised to 101 dB/1W/1M with virtually identical SPL.

 

Then there's the desired SPL volume. A system installation that I run in a 1000 seat room that does some lighter rock but a lot of folk/jazz/blues etc is just about right for the SPL (about 105 at the center of the house) that the client wants and is run with 5000 watts on FOH.

[ATOMICDOG1]

Well, my subs have a sensitivity of 101db 1w/1m (EV MTL1X)

I believe that my tops are 100 or 99db 1w/1m (SR4732A). Since we do a lot of hard rock/ metal, sometimes we are going for around 110-115dB spl at house center. Our large system is approximately 15,500 watts. We can do 1500 people outside with it easily. And if the music isnt metal, we can do more than that comfortably.

[rangerkarlos]

Hahahaha!

 

For a moment there I was pretty sure I could get by on 35 watts.

 

Now I see I need 2-250.

 

[tlbonehead]

From my thinking an actual 500 seating capacity club is huge,at least for around here. For the clubs I play,most of them under 250 capacity,I use about 3800 watts for subs and 1900 above 100hz. I use the same amps for my smaller outdoor shows but the sub amps are running at 2 ohms instead of 4,so I have 6000 watts to the subs.

[Guest Anonymous]

 

Originally posted by skunky_funk In the past I knew that a rough way to estimate the power you need for your PA is a certain number of watts per person. Say you wanna design a PA for a bar with a seating capacity of 500, how much wattage do you need?

 

Well... somewhere between 10 and 20 watts per person will generally get the job done.

 

There's much to consider though... just like asking how many cubic inches of displacement in a vehicle motor based on the per passenger capacity? The answer depends on what kind of performance do you want?

 

Personally, for a 500 seat venue... national acts... 5000 watts might do it... with the right stuff. 10,000 watts is probably closer to the mark (FOH only, right?... since you could easily power up another 5KW in the monitor rig in a 500 seat venue).

 

10Kw is kind-of a magic number. It's similar to 400 HP in a Pony Car. I'm a bit of a railroad fan (some say steam engines are (were) the pinnacle of "a man and his machine". I believe SR is a close second... ) anyway... the accounts of the Alco Class 4000 steam engines (Big Boys) are interesting. The 4000's were magical by most accounts (and some ran better than others)... and although there wasn't a certifiable method to measure the power... I believe the tractive force exceeded 100,000 lbs. and the brute horsepower probably topped 10,000 HP. Most accounts by the engineers was: "just put the throttle where-ever you want and the engine will respond... basically as an extension of your throttle hand".

 

I bring this up because: if it's up to me... I want a system were I can put the throttle anywhere I want and the system basically acts as an extension of my throttle hand. I don't want my tools to be my limiting factor (actually... I won't stand for my tools being the limiting factor... my ability better be the limiting factor because that's the only thing I can't improve upon with money... because money is simply the ways and means to do things... and money can be had... you just work for it... ability can't be bought). Generally 10,000 watts of SR power will accomplish this... and it's hard to explain... but there is a threshold in power where-in if the system is over the threshold... the system really comes alive (and no blinking red lights).

 

By the way... I'm not interested in flying in a plane with any less than a 1:1 power to weight ratio... same goes for sound systems.

 

I guess the big question is:

 

Do you want milk toast or steak? or something in-between?

[tomhole]

Originally posted by Audiopile By the way... I'm not interested in flying in a plane with any less than a 1:1 power to weight ratio... same goes for sound systems.

 

You'd enjoy a ride in my work vehicle

 

 

Although I'm not really 1:1 until I get rid of those external fuel tanks.

 

Tom

[Steve_B]

This is quite a complex question and depending on the situation rules of thumb can be pretty close or way out. Some of the factors involved, room volume, efficiency of the loudspeaker, have been mentioned. There are many others.

 

Let

[Old Steve]

I'm more concerned with cookies/person, beers/person, or slices of pizza/person. These are all much more direct and easy to calculate because you don't have to figure in diffent efficiencies between poweramps and speakers, room acoustics, room size, etc.

 

The "rules of thumb" in these categories are as follows:

All of these rules are based on the assumptions that the age spead, size and gender proportions are proportional to the general popluation.

 

A "watts per person" rule introduces too many variables, IMHO.

 

Tomhole: nice rig. If you ever want to watch a civilian puke, drop me a line, I'd love to go for a ride. Just don't release the drop tank when you're over my house.

[agedhorse]

SteveB... that pretty well sums it up!

[Guest Anonymous]

+1 there Tom on the commuter vehicle.

 

I'm guessing the "machine" is pretty much capable of what-ever you have in mind... point the joystick and it does it. I'm sure it will probably go "up" (or any other direction you have in mind) without hesitation.

 

I've always been curious about the physics concerning the diamond pattern behind rockets and jets. I'm guessing it has something to do with getting the air fuel mixure just right... and having plenty of both.