Tuesday, 7 May 2013

What's your EQ IQ?


What's your EQ IQ?



What is Equalisation? 

Equalisation (or EQ) is the boosting or cutting of specific frequencies to enhance or improve an audio signal. Home hi fi systems have basic EQ options to add or take away bass, middle and treble. Generally people just turn them up in the belief that more is better. 

On a mixing desk or in a DAW (digital audio workstation), the EQ essentially does the same thing as a hi fi EQ, but is higher quality and does so in greater detail. 

When some amateurs begin to record and mix their own music, they misuse their EQ and just like with their hi fi at home, they will automatically start adding EQ. If they hear a sound that has lots of bottom end, they might add a load of top end to compensate - thereby making the whole signal noisy. 

It is a huge step forward when you realise that taking frequencies away (subtractive EQ) before adding others (additive EQ) can improve your mix greatly. 

To begin with it's hard to pinpoint where in the frequency spectrum you should be EQ-ing a sound, so I've made some graphics that should help.


These are negative attributes so would require subtractive EQ in these frequency ranges.







This graphic shows where you might want to add EQ:







Below is an example of what sort of EQ decisions I would make on a vocal track.  This is a standard parametric EQ that you will find with any DAW. 

The first thing I notice is that there is a bit of rumble (see graphs above) from the singer's feet moving around on the floor. So I need to subtract the rumbling frequencies with a "low shelf" like this:




The next thing I notice is that the voice is generally a little too warm and boxy (see graphs above) so I will take away some of the boxy frequencies with a fairly wide "parametric" EQ. The width of the EQ curve is called the "Q". 

My EQ curve now looks like this:





I'm liking what I hear much more now but I'm still not quite happy. It is a little dull and needs a bit of detail and sparkle (see graphs above). So I boost the treble with a "high shelf". This gives more detail to the voice. 

The EQ now looks like this:





The vocal is starting to sound great. Although now I notice that there is a particular nasal, harsh quality to the recording (see graphs) that I need to eliminate. This sound is a little trickier to find, so I make narrow "Q" BOOST in the high mid range and then move it up and down the frequencies until I find the frequency that makes it sound really nasal and unpleasant. I now make that boost a CUT - thus taking away (subtracting) the nasal quality. 

The final vocal EQ curve now looks like this:







Learning to trust your ears and how to operate and EQ doesn't come overnight but hopefully these tips have helped. 

To reiterate: 


  • As adding EQ also adds noise, it is best to first take away any unpleasant frequencies before boosting the pleasant ones. 
  • If you are struggling to find exactly what to boost or cut in your signal but know it needs EQ-ing, try the sweep method I mentioned above. Make a parametric boost and sweep around until it sounds worse, and then cut that frequency out. 
  • Use the charts above to pinpoint the frequencies you need to cut or boost. 


Hope this helps!

Love, Bobby x