There are a few different types of equalizers out there, which is right for you?
It would seem that one of the easier things to do in the world of audio engineering should be EQing sound. However, that is not always the case. With all the available EQ's, each having different functions and features it can become quite confusing to some. There are Graphic EQ's, Parametric EQ's, Sweepable Graphic EQ's (sometimes referred to as Paragraphics EQ's to make it even more confusing), some people new to the trade just get frustrated and confused by the subject as has been the case from some people at our message board and other boards I used to frequent. The goal of this column is to explain what exactly the different EQ's are, what their function is and how they can be used to your best advantage.
This is, without a doubt, the most commonly known of EQ's. As shown in the picture (an Alesis M-EQ230 MEQ 30-band EQ), it is just a group of faders arranged from low to high frequency settings that are fixed at a specific frequency.
These are most often used in a "set and forget" environment such as ringing out a room. Which, to you who don't know, that means it is used to find the bad frequencies in a room and minimize them, such as in a club for live performing, it is used to get the most out of the system before feedback sets in. When feedback starts, you find the fader that controls the frequency at which the feedback is accuring and lower it. This gives a more even responce in the room, gives the sound engineer more headroom, and creates a better listening environment for all who are in the room. So it is set once upon installation and rarely touched beyond that.
In the studio atmosphere, it is also used like any EQ would be, just to help you get the sound you wan't from any instrument, or ringing out the control room as well.
The Parametric EQ is a different animal entirely. While it does help control frequencies and the overall EQ settings just like a Graphic EQ does, it has several advantages over a Graphic EQ.
Parametric EQ's allow you to pick very precisely which frequency you want to control via the "frequency" setting, and how big of a "Q" you want to work with via the "Q" setting. The Q is what confuses many people, if you look at the pictures here, you will se what I mean. If you set a wide Q, the frequency you choose will be the center of a very wide group of frequencies you will be affecting (the picture at the left may help you visualize it), it makes it a very loose adjustment. If you set a very narrow Q you can work on just that frequency with very little, if any effect on the neighboring frequencies (the picture at the right may help you visualize it). This is useful if you have a particular frequency that is really misbehaving on your snare drum, for example, you pick out just that band and get rid of it without creating a huge hole in your sound. Or, that is the theory anyway...
Sweepable "Paragraphic" Equalizer
This is a kind-of happy-medium between the two listed above. This a Graphic EQ with some, or all bands of the EQ sweepable. This means you can choose your frequency within a specified range, but does not give you the Q. By specified range I mean the manufacturer gives you a decent range of frequencies within reason, so you can't use the low shelf of the EQ and sweep it up to 10k but you can cover a wide range of frequencies on the lower end of the spectrum. Many recording and live sound consoles now have this type of EQ on their channel panels and even in the master section of the console. This is an awesome use for the EQ's. Outside of the console, I have never personally made much use of the sweepable units. That is not to say that you can't, I am sure some people do and do it well, I am only speaking for myself.
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