PA system - what power for outdoor use?...

Discussion in 'Location Recording' started by Jaike, Sep 1, 2009.

  1. Jaike

    Jaike Active Member

    Hi everyone,

    I'm working on a performance art piece which is to take place outdoors, in a field, so there's no reflection to work with.
    The audience will be composed of roughly 30 people, seated.

    I need to know what size/power PA I'm gonna need. I need to be able to achieve a decent sound level, not rock-concert levels, but not too far off. It needs to be able to cover the voice of some talking loudly 4-5 meters in front of the audience.

    I was thinking of using two 3-speaker systems (2 speakers + 1 sub), putting one in front, and one behind the audience. I thought this would give me good all-round balance (phasing is not an issue given the nature of the music involved), but I have no idea what power would be needed in the sort of context...

    Can anyone help me out with this? Thanks!
     
  2. dvdhawk

    dvdhawk Well-Known Member

    I don't think you need a speaker behind the audience. (There's a reason your ears and eyes are focused in the same direction). There's a lot of smoke & mirrors involved in 5.1 sound. A rear channel seems like it should be way down on your list of needs.

    Power requirement calculations are also VERY dependent on distance. Sound loses energy to a mathematical certainty over distance.

    That being said, I would think you could entertain 30 people outdoors / at a distance of 4-5 meters / at a reasonable volume / with 300watts - 500watts of a quality amplifier, and 2 to 4 decent speakers. This should give you plenty of reserve.

    I've had to provide PA for something similar (an outdoor wedding) with musical performances covering 200-300 guests seated in an area about 50yds wide x 60yds deep.

    Two 2-way 15" cabinets on tripods with
    600watts of amplification and
    a good mixer did the job very well.
    [all running from a generator]
    I had headroom to spare, but then again, I have fairly good stuff.


    Your results will depend on the quality (and sensitivity) of your speakers, and the amplifiers.

    Good luck!
     
  3. Jaike

    Jaike Active Member

    OK, thanks for the advice!

    And now for another dumb question: say I've got two 400W RMS pre-amplified speakers. One left, one right, does this mean my PA system is 800W RMS?
     
  4. jg49

    jg49 Well-Known Member

    400 + 400 = 800. Yes.
     
  5. dvdhawk

    dvdhawk Well-Known Member

    Your reasoning is sound and on paper that would be true.

    But published specs are usually over-stated on consumer / pro-sumer amps, it gives you some vague reference point at best.

    There's a world of difference between the methods used on spec pro quality touring amps and the methods used to exaggerate the specs and capabilities of the cheap ones. There are a lot of ways to fudge power specifications.

    So forget about the numbers, and see how those speakers sound.

    Are they sufficiently loud in your outdoor setting?
    Do they have tight bass response and clear highs and mids?
    Can you get the volume you want with headroom to spare?
    How do they sound 10m-20m away, or off-axis?
     
  6. BobRogers

    BobRogers Well-Known Member

    Just to give a specific point of reference. I've done several outdoor events for crowds under 200 with just a pair of JBL Eon G2 15inch powered speakers. Now, it was not heavy rock, so I wasn't looking for modern club-style bass or club-level volumes. But they would "cover the voice of some talking loudly 4-5 meters in front of the audience" with no problem.
     

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