If you’re following along at home, we’ve discussed how the GAIN control works to control the input level into the mixing console. When you plug in that guitar, microphone, mp3 player, etc, that signal goes into one of the many input jacks on the back of the console, gets amplified or softened by the gain control, and then goes to the EQ controls. The EQ knobs also amplify or soften the signal, but it does so only at selective frequencies. (More on this someday)
After the EQ, the signal splits and goes to a couple of different places. The most obvious is the main volume fader, the big control closest to you that slides up and down. Though there may be rare exceptions, this is generally used to control the main volume in the house speakers. At the same time, the signal is also going to anything that is marked “PFL”, which stands for “Pre-Fade Listen”. Pre-fade, as in “the signal before it is affected by the main volume fader.” These are additional outputs on the board that have their own volume control and are not affected by what volume you set on the fader. The easiest one to spot is the button labeled PFL that usually appears above each fader. Mackie and some other brands call this SOLO, but it is the same thing. Pressing this button takes the signal from that channel and sends it to the headphone/control room output of the board. Because it is pre-fade, you can listen to that channel in the headphones even if the volume is turned all the way down. The gain will still have an impact on the volume you hear on pre-fade outputs, but the main fader will not.
In addition to the PFL headphone output, there are also a number of pre-fade auxiliary (AUX) outputs on the console. The Aux controls on the mixing console are basically separate volume controls for different outputs. Your primary fader will control the house speakers. The Aux controls will control everything else from monitors and in-ears for the band to hear themselves, recording outputs, effects units, etc. There are two types of aux controls on the typical board, and they are labeled as Pre or Post, or they have a button to press to switch between the two options. The “Pre” controls are outputs that ignore the fader volume you set. The “Post” controls are post-fade, their output volume is in direct relationship to the main fader. For example, if you have your volume turned all the way down so you don’t hear anything, any monitors on pre-fade may still be making noise, the post fade outputs will be silent. As you turn up the fader and begin to hear the music in the main speakers, so too will you hear them in the post-fade monitors. The pre-fade monitors will stay at the same volume regardless.
The average mixer (in my experience) has 6 aux outputs. I’ve worked with some that only have 1, and some high-end consoles that have 16, and some digital consoles with far more. But 6 is the most common, and is likely what you will be working with at an entry level position. Typically the Aux 1 and 2 controls are pre-fade, 5 and 6 are post, and the middle controls have a button to switch between the two modes. The more expensive boards may have buttons on 1 through 4, or possibly all 6 controls. The point is, you may have a choice about when to use a pre-fade or post-fade output. There is no simple definition about which to choose. Most aux controls are used for the band to control monitors and everyone may have a different opinion on whether to be pre or post-fade.
The second most common use for auxiliaries is effects. Reverb is the most common effects unit you’ll find in the typical setup. The shortest description of a reverb unit is that it takes a singers voice and makes them sound like they are in a bathroom. Done right, this is a good thing, that’s why your own voice tends to sound better in the shower. In order for it to work, you have to send the singers voice to the unit and then have the echo effect get put back into the mix. This is where the post-fade aux works best. Turn up the aux for a given singer until you have just enough of the effect to sound good (subtle is good!), and as you turn up or down the volume on that singer, the effect will change as well. The effects processor’s output will likely have its own input on the board, or the console will have a set of controls labeled “Return” that are used to put the echo or whatever effect back into the house and/or monitor mix.
This is just an introduction to the AUX controls and the idea of pre and post fade levels. In upcoming posts I will go into more detail about mixing the monitors and useful information for making the most out of an effects processor.
The Questions in your Mind
December 23, 2007
As you are mixing some instruments and vocals together, there are several different questions you can keep asking to evaluate which channels need to be modified. At the typical youth event or concert, the primary question is “Is this as loud as I can get it?” Even in my own high school years I got a thrill from being in the front row or mosh pit and see how much noise I can sustain. Hearing the actual instruments or words to the song came second to thinking I’m cool because the subwoofer was disrupting my digestion.
But as I find myself mixing worship events and caring more about hearing the words and the subtleties between different instruments, the main question I try to keep my focus on is “What can I turn down?” It’s not that I don’t want anything to be loud, I still appreciate the quantity at times (and I’m not 30 yet). But the most common mistake when mixing is to turn channels up when something isn’t right. For example, the band is picking up volume and it’s hard to hear the singer, so you go and turn up the microphone volume. But then the guitar is getting lost in the background and you turn it up. Before you know it, your volume has increased too much for the room size or possibly distorting.
So instead, try to keep things at your target volume, and when you think the vocals or a certain instrument is being lost or drowned out…ask yourself what can be turned down to fix this mix. That way you keep your overall volume consistent, and you can highlight the quality of the mix without faking it with quantity.
As I think about it, this principle is a main focus for a lot of audio engineering aspects, not just the house mix. I apply the same principle when trying to use the equalizer to fix the tone of a channel or mix. When a channel doesn’t sound right and the EQ needs to be modified, I think of which frequencies can be cut and do so, only increasing on the rare exceptions when too many cuts have already happened or there really is a need for boosting just a single frequency by a small amount.
This principle is especially important when mixing monitors and even in ears. The biggest trap you can fall into is turning up instruments or microphones when a musician asks you to. This is especially problematic when a single monitor speaker is shared between two or more musicians. For example, the lead singer says they need more vocal and you turn it up, then the guitarist says he needs more. As soon as you turn the guitar up, the vocalist again says he needs more. Neither realize that the vocal range and guitar range are close in frequency range and are literally drowning each other out, competing for which input has more dominance in the monitor. And you become stuck with this really loud monitor that is competing with and possibly overpowering the FOH (Front of House) speakers.
With dedicated monitors or in-ears, you can evaluate which instrument or channel is most important to the musician and make sure the mix reflects that, turning down other channels until the instrument they want is at the forefront (which 99 out of 100 times is their own instrument or vocal). With shared monitors, you will have to communicate with the musicians to work out a compromise, or try to arrange the stage so that complimentary (instead of competing) instruments are sharing the monitor feed. When the guitarist is asking for more volume, you can tell him or her that the monitor is as loud as you can allow it and ask if other instruments can be turned down instead. Usually the people sharing the monitor can agree to some kind of compromise.
