Alesis DEQ230D User Manual

 

At their inception, graphic equalizers relied solely on a form of  

equalization known as "Variable Q." The DEQ230, on the other 

hand, is what is known as a "Constant Q" equalizer. This method 

of  equalization is a relatively recent development in the history of  

sound reinforcement and recording technology. As you will see 

illustrated in the charts in this section, the Constant Q method 

allows for a higher degree of  control over the sound being 

processed because of  its significantly greater accuracy.  

 

Before we go any further, it's time for some definitions:  

 

Q   

 

The range of  frequencies affected by a  
band  

 

Variable Q 

A process in which the range of 
frequencies affected by a band changes as the 
amount of  gain is cut/boosted  

 

Constant Q  

A process in which the range of   
Frequencies affected by a band stays the  
same as the amount of  gain is 
cut/boosted  

 

It may help to define these terms visually as well.  

 

In the following illustration, we see the three basic terms that 

govern the operation of  a single band. The vertical bar of  the 

graph represents decibels of  cut/boost, and the horizontal bar 

represents frequency in Hz. The dotted line leading to the center 

of  the curve indicates the frequency at which this band is set. You 

can see that in this example, Q covers a range of  frequencies from 

about 200 Hz to about 5 KHz.