Product Feature: Equalizers

We've all heard it. That almost ear piercing squeal, or low rumble. Perhaps you've suffered through a meeting or service as you listened to a faint ringing or hollow sound that makes you want to run for the controls or the door! You know what I'm talking about - Feedback! Or how about this: you are responsible to run your church or organization's sound, but you can never quite get the speaker's voice to sound right.  How many events has this gremlin either ruined or at least caused an unwanted distraction?

Well, this time we are going to look at one of those handy fix-it tools that can save a lot of headaches - Equalizers. They are not a cure-all or total fix for poor acoustics, but they can be a very large help in correcting some of the above mentioned scenarios.

Equalizers come in several formats and capabilities. To simplify things, we'll break them down into two basic groups: Graphic and Parametric. A graphic equalizer gets its name from the layout and use of its controls. Usually, it will have 16 or 31 vertical "sliders" to cut or boost offending frequencies. After the desired frequencies are adjusted, you can look at the pattern that the sliders form and get a good idea of the effect the equalizer is having on the signal.

      
       ASHLY GQX 3101 31 Band Graphic EQ 

Generally, Graphic equalizers are best suited for tone shaping and limited feedback control. They help "smooth out" the response and compensate for some equipment and acoustical deficiencies. They are not well suited for notching out unwanted frequencies or heavier feedback because they cut out too much of the "good" signal. They are "fixed frequency" which means there are only 16 or 31 different frequencies that can be adjusted. For example, if you needed to cut a 1350 HZ problem, you would have to adjust the closest slider to 1350 to get the desired effect. In doing so, you also adjust some of the adjacent frequencies that did not need adjusting. What do you do? Use a parametric equalizer!

A parametric equalizer has an entirely different control format than its Graphic counterpart. Instead of 16 or 31 fixed frequency sliders, there are several groups of controls to adjust and shape frequency response. A parametric EQ will usually allow fewer frequencies to be adjusted, but much more control over what can be adjusted. A typical parametric EQ may allow five to seven frequencies to be tuned. Each of the five or seven frequencies will have about 3 characteristics that may be set. 1) The actual frequency you want to adjust. 2) How much you want to cut or boost that particular frequency. 3) How many frequencies above and below are effected. 

With this arrangement, offending frequencies that are involved in "ringing" or feedback can be cut out without removing adjacent frequencies that are necessary or desired. Most of the time, only 3 to 5 "problem" frequencies will need to be notched. This arrangement minimizes sound "coloring" that unnecessarily "chops up" the sound quality.

     
      ASHLY PQX 571  7 Band Parametric EQ

In the last few years, there have been several innovations to to these two formats. The most noteworthy is digital signal processing (DSP). Now, these functions can be performed with a microprocessor "chip". The advantages are many, but some of the more obvious are: 1) Access to controls is limited to someone with a computer that has the appropriate software and password. 2) Many additional functions can be included at greatly reduced cost, such as compression, delay, etc. 3) You can have both Parametric and Graphic equalization for the best of both formats.

Product Feature #1: QSC DSP- 3

The QSC DSP- 3 Digital Signal Processor has two independent channels of signal processing. Processing options include: Multiple  Parametric EQ Filters, Multiple Delays, Dynamics Processor, Output Peak Limiter, High and Low-Pass Crossover Filters, Noise and Tone Generation. The DSP- 3 also has presets, which allow several different configurations to be stored and recalled with a simple contact closure. Also, the unit is configured with software that allows different  processing components to be "dragged and dropped" onto a screen and then signal paths are drawn to connect the components. The configuration is then uploaded into the DSP- 3. The module is designed to work independently, or it can be connected to the rear panel of some QSC amplifiers. For more information, click Here.