Crown Audio by Harman

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Glossary



Please explain mixer connections, equalizers, compressors, and groups.

We were just gifted a very nice sound-mixing board and I am in charge of it. While I can handle the basics I would like a good resource where I can learn what all the terms used in mixing mean. I read the manual that came with it and I still don’t understand the concepts behind hooking the sucker up, what jacks are best to use, what groups and subgroups are, etc. Got an idea for a good resource?

Our monitors and mains go straight from mixer to amp to speakers. Why would you use an equalizer between mixer and amp? Isn’t that what the mixer is for? And what is a compressor used for?

Would I use the grouping to combine several channels into one for say a monitor for just the vocalists?
Pete Hanlon

Reply: I'd recommend the book "Practical Recording Techniques Fourth Edition" available at amazon.com. It covers mixers and mixer operation, as well as sound, signals, mics, mic techniques, effects, digital recording, sound quality, and so on.

Here are the basic mixer connections to make:

  • Connect each mic to the stage box (snake).
  • Connect each snake XLR connector to each mic input XLR connector.
  • Connect the mixer master output to your graphic equalizer input, and connect the graphic output to your house power amp input. If you are not using a graphic equalizer for the house speakers, connect the mixer master outputs to the power-amplifier inputs for the house speakers.
  • Aux knobs can be either monitor sends or effects sends. In other words, turn up an aux knob to make that mic signal louder in the monitor speakers, or to put more effects on that mic signal. Aux knobs used as monitor sends are set to pre-fader , while aux knobs used as effects sends are set to post-fader.
  • If aux 1 (for example) is your monitor send, connect the aux 1 send connector to the graphic equalizer (if any) used for the monitor speakers, and connect the graphic equalizer output to your monitor power-amp input. If you are not using a graphic with your monitor speakers, connect aux 1 send to the monitor power-amp input. Set all monitor aux knobs to pre-fader so that the fader for each channel does not affect the monitor level.
  • If aux 4 (for example) is your effects send, connect the aux 4 send connector to the input of your effect device. Connect the output of the effects device to Bus In or Effects Return connector on your mixer. Another option is to connect the effects outputs to the line inputs of two extra input channel strips on your mixer, and have that be the effects-return level control. Set the effects-send knobs to post-fader so that the fader level also controls the amount of effects. Set the dry/wet mix control on the effects unit all the way to wet (100% effect). You'll control the dry/wet ratio at the mixer using the aux send controls and effect-return controls.
  • If you are recording the service, connect the mixer REC OUT or TAPE OUT connectors to the recorder line inputs.
  • If you need to insert a compressor in-line with one of the mic channels, find the mic channel on the back of the mixer, and connect its insert send to the compressor input. Connect the compressor output to the insert return on the same mixer channel. If there is only one insert jack per channel, the tip of the jack is send and the ring of the jack is return, so use a stereo phone plug at the mixer going into two plugs (in and out) at the compressor.  

You can get by without a graphic equalizer between mixer and amp, especially if your house speakers are really good. However, if you have a graphic equalizer, you use it to flatten the frequency response of the house speakers. Mixer EQ is just for individual instruments and vocals, not for the entire system.

It's also common to use a graphic EQ between the monitor send (aux out) and the monitor-speaker power amp. That EQ is used to reduce the levels of frequencies that feed back. You also can use the graphic EQ to reduce the bassy sound in the monitors caused by microphone proximity effect (the bass boost that occurs when directional mics are used up close).  The monitor signal from the board is pre-EQ, so turning down the bass (low frequencies) on the mic channel does not turn down the bass in the monitor speakers. That's where a graphic EQ can help: turn down frequencies a few dB below 200 Hz or so. Then the monitor speakers won't sound too bassy and muddy.

A compressor is used to reduce the dynamic range of whatever signal you pass through it. For example, a lead vocalist might suddenly sing a very loud note, blasting the listeners. The compressor is an automatic volume control - it turns down loud notes so they don't get too loud. If this isn't a problem in your church, you don't need a compressor.

The groups are for the house speakers, not the monitor speakers. You might assign all the vocal mics to Group 1 (also called subgroup 1 or submix 1). Then you can control the overall level of the vocals with just the group-1 fader. Start with the group fader and master fader about 3/4 up. You don't have to use groups, but some people find it convenient. If you don't use groups, just assign each mic channel to the stereo mix bus (the master stereo output of the console), and turn down all the group faders because they are not being used.

To confuse things, some consoles use Group 1 and Group 2 as the main stereo output channels. Other consoles have groups plus a separate stereo master output channel.

The aux knobs can be used for monitor mixes. I assume that your mixer has several aux channels (aux-1, aux-2, aux-3, etc.) Each aux number is a separate monitor mix, feeding a separate monitor power-amp channel, feeding a separate monitor speaker.

You might use all the aux-1 knobs to set up a monitor mix for the vocalists. Connect aux-1 out to the power-amp channel for the vocalists' monitor speakers. Then use all the aux-2 knobs to set up a monitor mix for the drummer. Connect aux-2 out to the power-amp channel for the drummer's monitor speaker. Use Aux 3 for the piano player, and so on.

For example, let's say the vocalists need to hear only the piano and vocals in their monitor speakers. You would  use all the aux-1 knobs across the console to set up a monitor mix for the vocalists. Turn up the piano channel's aux-1 knob about halfway. Turn up the vocal channels aux-1 knobs about halfway. Turn up the aux-1 master knob (if any) about halfway. Make sure the vocalists can hear the monitor mix, and adjust it according to what they want.

Similarly, suppose the drummer needs to hear only the piano and bass. You might use all the aux-2 knobs across the console to set up a monitor mix for the drummer. Turn up the piano channel's aux-2 knob about halfway. Turn up the bass channel's aux-2 knob about halfway. Turn up the aux-2 master knob (if any) about halfway. Make sure the drummer can hear the monitor mix, and adjust it according to what the drummer wants.

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