Differences in Eq

[Cheb Abdou]

Hey, I've been reading a lot about Eq, but I am still a little fuzzy on the differences between parametric, graphic and shelf equilization. Whats a easy and clear way to differentiate and remember the key differences among the three?

 

[Freeform]

From http://www.baconmusic.co.uk/tutorials/story.asp?contentID=305

Shelving E.Q - Shelving E.Q. is a basic 'treble' and 'bass' equalizer, or a 'hi-freq' (treble) and a 'low-freq' (bass). Basically shelving E.Q works the same as the bass and treble controls on any decent home hi-fi. The 'low-freq' or 'bass' control simply boosts or cuts the high frequency's, and the 'hi-freq' or 'treble' control cuts or boosts the high frequency's.

Sweepable E.Q. - Along with the bass and treble controls there may be a control labeled 'mid'. This unlike the bass and treble is uncommon in home hi-fi's and is mostly only found on mixing desks. This control effects the frequencies in-between the hi and low frequencies. Characteristics of sweepable E.Q. are that the band width and the center frequency are both fixed. Therefore it sweeps around the mid range frequencies as a sort of mid range 'block' altering frequencies as it goes along. Mid range E.Q. can be used to create a cheap flanging effect as this sort of filtering creates a sort of "wah" in the signal.

Parametric E.Q. - Parametric E.Q.'s are basically the same as the Sweepable E.Q. with the advantage that the band width and center frequency can be altered. This allows the mid range 'block' mentioned before to alter its shape and give out more a impressive range of equalization functions. The bandwidth is often called the Q control and is measured in octaves. Octaves higher move as a doubled frequency high but ½ frequency low. Therefore an octave higher than 5kHz would be 10kHz and lower would be 2.5kHz

Graphic E.Q. - Graphic E.Q.s are like having around loads of shelving E.Q.s in one unit. Although a complex beast put simply the graphic E.Q. is lots of little filters each with a fixed center frequency control that like the Sweepable E.Q. cannot be changed. The control that you do have with a graphic E.Q. is the amount of cut or boots in each frequency band. The actual sliders them selves are what gave the graphic E.Q. its name.