How To Properly Use The EQ In Your P.A. System

Next to improper gain structure, incorrect or poor use of the equalizers in a sound system is probably the biggest cause of a bad sounding mix. Too often I see sound persons doing all the things they should not be doing with their EQs and not doing the simple things they should be doing.Poor EQ management not only results in a bad sounding mix, but it can cause your amplifiers and speakers to work much harder than they need to to get the same volume as if the Equalizers were set “correctly”.

I put the word “correctly” in quotes because all things in the mixing world are somewhat subjective. There’s no empirically right or wrong way to do anything but there certainly are techniques that the sound community in general agree work better than others. In this post, I’m not going to cover any of my special techniques; only those that I know 90% of my colleagues agree are the best methods.

We’re simply going to call this list of tricks “6  Rules To Using Your EQ Wisely

1. Know why you’re changing what you’re changing. If you’re about to make change in your equalizer and you’re not 100% sure why you’re doing it, then, chances are, you’re not going to get the result you’re hoping for. The EQ is not a place to be “winging it” during a show. Experimentation is encouraged when you have the system set up in the backyard or prior to the gig, but random changes during the show should be avoided unless you have a really bad feedback situation, and even then if you’re not sure why you’re about to change something, pulling the faders back is still often the best solution.

2. If it ain’t broke, don’t fix it. If you look over my shoulders during a show you will see that my eqs are mostly flat. I often do entire shows with all my channels EQs (except for vocals) at the 12 o’clock position and you will only see minor cuts being made on the 31 band eqs on the FOH and monitor mixes. The equalizer controls are not “tone” knobs. They should be used only to correct problems, not to flavor the sound. Your job is to successfully reproduce the sound of the instruments on stage. More often than not, putting a quality microphone in front of something on the stage and bringing the fader up is all you need to do to accomplish that. (see rule 1)

3. If it is broke, don’t fix it with the EQ. To often, the equalizer is used to correct problems that are either systemic or to fix a bad audio source. In the case of the channel strip EQ, changing the mic position, getting the artist to adjust the source ( “Can you take a little bass off the guitar amp?”) is a preferred solution than trying to use the EQ strip to make up for a bad sounding source at the microphone. In the case of overall system issues we will often see sound people doing something to all the channel strips, like rolling the bass off or boosting the mids, or they will make drastic changes to the system EQs like pulling down all the bass or mid or upper sliders. This is an indication of a much bigger problem such as an improper balance between your  tops and your subs or really poor performing speakers. Anytime you make sweeping changes to your equalizers you can bet the farm your real problem lies elsewhere. Always attempt to fix the problem at the source before going to the EQ.

4. Use  HPFs where you need them. Most modern boards come with an HPF or High pass filter on each channel strip. What this does is to take certain frequency, often 80 or 100 hz, and apply a steep filter there to only allow frequencies above that to pass thru that channel.  This is especially helpful on vocals and higher tuned acoustic instruments since they do not need those frequencies. It keeps the bass sounds from the stage from leaking thru those microphones and muddying up the mix, reduces handling noise and cuts down on “popping” sounds from words that begins with “P” and “B”. If you do not have an HPF, than turning the “low” EQ knob to the left will give you the same effect. This is an extremely effective technique for cleaning up a mix that, sadly, a lot of sound people do not understand or use.

On most boards it is a fixed frequency and useful only on instruments with no lower range, however, if you have digital board and your HPF frequency is adjustable, it can be useful on almost every channel. You need to adjust it up or down depending on what you’re miking. But before you do that, see Rule #1.  A properly set up system will also usually have a HPF on the subs set somewhere around 30-40hz to keep sub-woofers that can’t go that low from wasting amplification power trying to reproduce those lower frequencies and to protect the speakers themselves.

5. Always cut first.  I rarely ever turn any channel eq knob up nor push any slider up on my 31 band EQs. Most changes that need made are because certain frequencies are too prevalent on the mix, not because others are lacking. Do not make the mistake of boosting the highs, when in fact, you need to cut the lows a bit. When you are cutting rather than raising you will also find that you need to make much smaller adjustments to get the desired result. Rule of thumb in any mixing scenario should be to remove what’s too loud as your first resort, only boost something when it is truly lacking in the mix, never to put it overtop of something else that needs brought down.

6. Make subtle changes.You rarely have to cut more than 3db on any slide on your FOH EQ. Same applies for channel strip EQs. If you find yourself cutting more than that you probably have another issue that needs addressing.  There are exceptions to this rule, for example, sometimes ringing out monitors will require as much as 6 db cuts, or occasionally you will come across low frequency room nodes that require drastic cuts. While repositioning speakers, microphones etc. is the best solution, in many venues it simply isn’t practical and sometimes deep cuts on 1 or 2 frequencies have to be made. Always make the least amount of change you can get way with. Every time you cut a frequency on your FOH EQ by 3 db, it requires twice as much amp power to bring that frequency back to zero, on channels that need it. It is my personal opinion that if you find yourself cutting more than 6 sliders on your 31 band EQ  you have system or a source problem that needs addressed.

In Closing

This is a very generalized view of using equalizers but the main points that should be gleaned from this post is that they should be used very sparingly and very deliberately, not for tone shaping as much as for problem solving. You will also find that as the quality if the speakers you are using goes up the usage of your EQ will go down. A lot of needed EQ is due to poor coverage from your speakers. If possible obtain a copy of the frequency response chart for all the speakers you own.

Every speaker has frequencies that it produces better than others.The frequency response chart can give a good starting point to see which frequencies you’re likely to have problems with, either being too hot, or lacking.  When working with new speakers they can give you a baseline for quick and dirty baseline EQ setting.The flatter the response chart is, the less EQing you will likely need to do to get a good sound. Use these,however, with a grain of salt, as the data is sometimes not 100% honest and other factors such as speaker position in the room, and natural room nodes can alter the true acoustic output of the speaker cabinet.

This is also a reason why you should not mix and match speakers, especially stage monitors, because each will have unique changes needed at the EQ to get a flatter response. Mixing different cabs can result in a situation that’s almost impossible to EQ properly, especially if they are sharing the same monitor send. Because each speaker may need 1 or 2 different frequencies pulled out of it to keep feedback in check having different speakers on the same monitor EQ can result in so many frequencies being pulled out that there’s almost no usable sound left.

Everything in this post has been specific to either channel strip EQs or 31 band graphic EQs. We have not even touched on the use of parametric EQs. Parametric EQs are a wonderful tool, if used properly and can be very destructive if not used properly and my suggestion is not use them until you understand them. I’m sure I will be covering them in a future post.

 

Until then, happy mixing.

 

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