How To | Set proper gain structure in Q-SYS

Discover practical tips for achieving optimal gain structure in Q-SYS audio systems, ensuring clear and consistent sound performance.

Updated at April 30th, 2024

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This article provides guidance for best practices in gain structure. It covers topics such as preparing sources, input gain structure, microphone considerations, output gain structure, and output processing and dynamics. Follow the steps outlined in this guide to ensure optimal audio performance.

Procedure

1. Preparing Sources

These include analog program sources, analog mic sources, and digital streaming sources.

  • Analog Program Sources: Play program at ‘nominal’ level.
  • Analog Mic Sources: Calibrate with talker at normal distance and level.

Important

  • Fully decrease gain on all amplifiers using gain knob (or Q-SYS outputs if no controls) until input and DSP gain structuring is complete.
  • Keep the gain structure of calibrated sources at ‘unity’ (1:1) through the DSP, where possible.
 
 
 

2. Setting Input Gain

All analog inputs: Adjust the Preamp Gain at the Q-SYS input block to reach -20 dBFS nominal.

 
 

3. Configuring Microphones

Check Microphone Signal to Noise

  1. Set the preamp gain to reach -20 dBFS nominal.
  2. Have the talker be silent.
  3. Verify noise floor at input is at least 15 dB below nominal (-35 dBFS or lower) - see callout 3.
    • If so, proceed.
    • If not, poor signal-to-noise ratio must be addressed at the source.

Microphone Dynamics

  • Use an Automatic Gain Control block to balance QUIET talkers.
  • Use a Compressor block to balance LOUD talkers.

Managing Feedback

  1. Insert a Notch Feedback Controller in the microphone signal chain.
  2. Bring the microphone into feedback and observe the feedback frequencies.
  3. Attenuate the microphone Parametric EQ block - see callout 3.
  4. When completed, remove the Notch Feedback Controller from the signal chain.
  5. Repeat for each microphone.

 
 

4. Choosing an Automixer

Automixers are best for “spoken word” applications such as presentations or conferences. There are two types.

Gating Automixers

  • Use this type for systems with any number of microphones.
  • These are suitable for rooms that have acoustically reflective properties.
  • Don’t set MAX NOM higher than 3.

Gain Sharing Automixers

  • Use this type for systems with 8 or less microphones.
  • These are suitable for rooms with good acoustical properties.
 
 

5. Adding User Gain Controls

  • Do not place gain controls ahead of automixers.
  • Avoid multiple user gain components in a single signal path.
  • Set reasonable limits on user gain controls.
 
 

6. Setting Output Gain

Assuming a complete signal path from input to output:

  1. Play the calibrated input source.
  2. Slowly increase the amplifier gain knob in each zone until the required SPL is reached.

    Tip

    If there are no controls on the amplifier, use the Output Gain controls rather than Digital Gain to achieve the required SPL.

     
  3. Make sure that the signal is not clipping at the Q-SYS output.
 
 

7. Set Output Processing, Dynamics, and Calibration

Processing

  • If you are using QSC or Q-SYS loudspeakers, add them from the Inventory in Q-SYS Designer Software (QDS).
  • If you are not using QSC or Q-SYS loudspeakers, use the Generic Speaker block (also in the QDS Inventory) and configure it using the loudspeaker manufacturer's suggested EQ.

Dynamics

Use the Peak Limiter to avoid output clipping:

  • This should be the last DSP block in the signal chain.
  • Set a -3 dBFS safety threshold level.

Calibration

Use the Analog Output gain setting to adjust the Max Output Level to the clipping point of the next device in line.

 
 
gain gain structure automixer microphones mic

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