Sound Reinforcement

Proper gain staging (or proper gain structure) for live sound

• *First* turn off amplifiers (main speakers and stage monitors are often "active" which means they have amplifiers inside the speaker)

• on the mixer

  • set channel volume faders and main outs to Unity (ØdB)

  • set the preamp gain knob to lowest setting

  • with headphones (or just visually) set proper gain structure for each channel:

    1. press PFL/SOLO button on the channel

    2. engage HPF if source has no low end (always engage for vocals)

    3. slowly bring up preamp gain knob as performer sounds into the mic until the VU meter averages around -18dB and never peaks at higher than -6dB

    4. unSOLO the track and perform the three steps above with the next channel, etc.

• *Last* (after all channels have been setup individually) have everyone perform together and with volume knob of amplifiers (main speakers and stage monitors) turned all the way down, slowly turn up volume knobs on amplifiers until you reach the desired volume in the space.

Feedback

• reasons for feedback:

  • mic too close to PA speaker

  • mic too far from source being amplified

  • too many mics

• ways to minimize feedback issues:

  • experiment with the placement of a microphone

    • the closer the microphone is to the source the more the preamp gain can be lowered

  • placing the speakers between the microphone and the audience (speakers along the front of the stage) can greatly lesson feedback issues because the microphone will not pickup its own amplified signal

  • use directional mics to isolate sounds being picked up

  • add acoustic treatment (absorption) to especially "live" rooms with many hard surfaces

  • add an audience! (rooms without an audience sound very different than rooms with no audience)

  • use a spectral analyzer to identify feedback frequencies and fine tune EQ