A colleague of mine has recently discovered the joys of mixing Front of House without the compulsory addition of a 31-band graphic equalizer across his main left and right output, and is now espousing his newfound technique as though it were a revolutionary breakthrough in live sound reinforcement. While (in theory) it is true that the sound is better without this extra piece of outboard gear, the idea is neither revolutionary nor new, and for all of those who find this approach intriguing, may I suggest that you not unscrew the equalizer from your rack just yet? A one-third octave 31-band equalizer is one of the many tools available to an audio engineer, and when used correctly in conjunction with amplifiers and speakers, it can prove to be a very useful asset as a component in the sound system. When used improperly, the resulting effect can be phase-shifting and lack of system response. Excessive boosting of the graphic, especially in the lower frequencies, can stress the amplifiers and the loudspeakers, while at the same time reduce overall headroom of the system. Extreme cuts in the graphic equalizer can cause a noticeable loss in segments of the program and, again, is not a desirable effect, but I am getting ahead of myself. I should really start at the beginning for this to make any sense at all. Bear with me while I explain my version of "gain structure."
I say "my version" because while there are some certain rights and wrongs in setting up one's gain structure, there is no definitive way to build a great mix. Anyone can get behind a console and mix, and while a little knowledge certainly helps, one does not need an advanced degree in electrical engineering to be an audio engineer. Much like driving, it is not necessary to know how to build the car as long as you learn the essential tools needed to drive the car.
Think simply by trying to think of the whole and not just the individual parts. The idea is to take an audio signal, send it to a pre-amp, then to an amplifier and finally to a loudspeaker, with the final result being a clear, amplified reproduction of the original signal. To achieve this end, it's always nice to have a computer and some software that applies to the speaker system, but unfortunately, this is not always the case. Thus, I have devised my own method, which I will share with you now: I usually take a Shure SM58 microphone, and on the input strip, roll off about 3dB of 400Hz. After that, I solo the channel and, while doing my best James Brown impression, I yell, "Ha!" into the mic as loud as I can while turning up the input until the VU meter peaks at zero. I then set my output fader of the channel to zero and send the signal to the left and right main out, both of which are also set at zero. This routine is often the cause of much snickering and unwanted attention, so I try to get past this part of the process as quickly as possible.
Then, with the amplifiers open all the way, I adjust the levels of the crossover by turning down all the fields and then adding them back. I balance the highs, high-mids and low-mids as I listen to myself speak through the speakers, utilizing the typical droll soundman patter: "Check one two, one two, check, check, check." Once I achieve the desired sound, I then go into the DSP to adjust certain errant frequencies. Most digital signal processors have two parametric equalizers per field with which one can finetune and contour the frequency response of the console output for improved intelligibility. I try to tune the system so that my voice sounds unaffected and natural at FOH position. I add the subs in while the band is playing since some music requires the subs wide open, while other types of music–such as jazz, folk and classical–do not require an abundance of sub frequencies. At this point, with the 31-band graphic still flat, the system should be quite responsive and sounding clear and natural, regardless of musical style.
Touring engineers know that it is impossible to do a show without the proper amps and speakers, which is why most sound riders on contracts state that the system should be capable of 120dB at the FOH position. If there is enough power and the proper amount of well-placed speakers to cover the venue, then it should be relatively easy to get a decent mix without using the graphic EQ, but if system isn't large enough for the venue, or if it is incapable of reproducing certain frequencies, then it makes it very difficult to set up a decent gain structure at the console.
The system is now set for the engineer to come in and mix, and it doesn't matter if the engineer likes to do a fader mix or to do an input mix with all the faders at zero. The gain structure of the system should, at this time, be balanced, and hopefully, the sound emanating from the loudspeakers is an accurate reproduction of the input signal. A good way to check the sound of the speakers is to cue up an audio program in the headphones and compare the headphone sound to the speaker sound, with the signal output to the speakers at peak level. Instead of immediately reaching for the 31-band graphic to balance any wayward frequencies, try equalizing the input of the program from the channel strip instead. The idea is to maintain the dynamic range of the loudspeaker system so that the mixing console becomes a responsive tool without having to make drastic cuts or boosts in the channel EQ. If it becomes apparent after the show starts that a few frequencies need to be cut a bit to clarify the sound, then I might reach over and notch the graphic, but these frequency cuts should be minor (generally, no more than 3dB) and usually no more than two or three frequencies at the most.
Gain structure is commonly known to be how one sets up the various increases in input and output signal power. While many gain structure articles explain the mechanizations of setting up the mixing console, it is important to note that if the speaker system is not properly set, then it will be harder to build a great mix. That is when an engineer might find themselves struggling with the equalizer or other various components of the system.I am not saying that everyone who mixes on their small system can go out and mix a large show, but I am saying that the goals are the same. That goal is to amplify the program and fill the space with the most pleasing and natural sound possible.
