output levels on powered speakers- how to set

Discussion in 'Recording/Live Sound' started by tammuz7000, Mar 3, 2012.

  1. tammuz7000

    tammuz7000 Member

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    I got a set of ev live 112p powered speakers and they sound awesome. I was wonderings what is the best way to adjust the levels on the speakers and the mixer. There are 3 knobs on the back, one for the overall speaker output and the other 2 for the the indivual channels....so should i just put them both in the middle?...i am linking them together and then running a cable to a yamaha mg10/2 mixer..and using a mic and an acoustic guitar into the mixer.

    also on my yamaha mixer there are levels for each channel and a gain for each channel and a overall level.. can anyone tell me the best way to use these..levels with each other...i set the level for the channel at 3/4, the level for the gain at say 1/4 to 1/2 and then turn up the overall level..

    there has to be some way that makes sense..for the gain and levels...

    tom
     
  2. rokpunk

    rokpunk Member

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    set every part of your chain at unity and go from there.
     
  3. Rex Anderson

    Rex Anderson Member

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    How to set gain structure 101:

    Start with the level on the speakers all the way down or very low so you can just barely hear something coming out.

    Set the input faders on the channels and the output master faders on the console at 0 or unity if there is a mark.

    Sing into the mic at a loud level and bring the input gain knob up and meter it so you get 0 VU on the channel. Same thing with the acoustic guitar channel - play loud and hard and set the input gain knob so it solo's up at 0 VU or close to it. This optimizes the gain structure on the input channels.

    Turn up the input level on the speakers until you have the volume you want in the room. Adjust balance between the guitar and vocal with the channel faders on the console.

    This is a rough way to optimize gain structure. You want to set input gains on channels so they are high enough but not clipping (red light on channel meter?) and run the output of the mixer so it is around 0 VU on the meters. If you don't get the input gain trim set correctly, nothing down stream will sound good. If it is too low, it will sound wimpy and noisy, if it's too high, you'll hear distortion.

    Depending on the size of the room you are in, you might just be able to barely turn up the speakers before they are too loud, or you might have to crank them up full and not have enough level (doubtful).

    If it's too loud with the speakers just cracked open, drop levels back at the console, trim back the input gain, drop the faders a bit, but try to keep input and master output faders no lower than -10.

    Gain structure goal is to maximize signal to noise ratio and minimize distortion. Console faders like to be somewhere near their 0 point. It's best to get the gain structure on the console right and then turn up the volume on the speakers, but if you can barely open up that control, you have to back off levels on the console so you can open up the input gain on the speakers a bit.
     
    Last edited: Mar 4, 2012
  4. tammuz7000

    tammuz7000 Member

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    Thanks very much... i think i understand the basics now..and will give that a shot. I was hearing way to much noise and was how I was adusting them.

    -Tom
     
  5. silver surfer

    silver surfer Member

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    Rex - Thanks so much. I've been doing it differently for many years without a noticable problem, but recently have been having problems with the limiter on my new QSC K12 causing the speaker to temporarily shut off. Followed your method and bingo - can get the loud volume I was looking for and no limiter problems. Tone of everything seems to be a little better also. Thanks again.
     
  6. MikeVB

    MikeVB Supporting Member

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    What is "VU?" Thanks.
     
  7. Rex Anderson

    Rex Anderson Member

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    VU stands for Volume Unit-it is an old metering style, but is still a common unit. The VU meter shows average levels instead of peaks. Both offer useful information and a combination is ideal.

    For pro audio it is defined as
    0 VU = +4dBm

    In dBm,
    the m stands for a 1 milliwatt reference. What voltage across a 600 ohm load (very old school audio in the US used 600 ohm transformers on outputs and inputs-same as the telephone system) creates 1mW? .775 Volts = 0dBm
    +4 dBm = 1.228 volts. This is
    the reference voltage we use to calibrate professional audio systems.

    Now, because we don't use 600 ohm transformers (a matching system for maximum power transfer) any more and use a bridging system instead (low output impedance and high input impedance for maximum voltage transfer), we use dBu (unloaded) as the unit. dBm and dBu are interchangeable because they use the same reference voltage for 0 (.775 volts = O dBm and also 0 dBu).

    From this handy web site:

    http://www.sengpielaudio.com/calculator-db-volt.htm

    The origin of the index of dBu comes from "u = unloaded" and dBV comes from "V = 1 volt". Some say:
    The "u" in dBu implies that the load impedance is unspecified, unterminated, and is likely to be high.


    What is dBu? A logarithmic voltage ratio with a reference voltage of V0 = 0.775 volt ≡ 0 dBu
    What is dBV? A logarithmic voltage ratio with a reference voltage of V0 = 1.0000 volt ≡ 0 dBV
    The home recording level (consumer audio) of −10 dBV means 0.3162 volts, that is −7.78 dBu.
    The studio recording level (pro audio) of +4 dBu means 1.228 volts.

    The maximum undistorted level of audio amplifiers in the US is +24 dBu. Some newer equipment running on higher voltage rails has +32 dBu capability.
    Domestic gear with a −10 dBV level is usually unbalanced. Studio gear with a +4 dBu level is always balanced.


    Google VU meter to learn more about it.


     
    Last edited: Mar 6, 2012
  8. orogeny

    orogeny Supporting Member

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    rex anderson can run my boards anytime. . . .

    spot on

    input gain
    channel volume
    'master' volume = your powered speaker now

    and remember that fx lend their own 'squeal' factor, especially on the high end. this is damn near a kung fu issue.
     

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