One of the areas that is important when using equalisation to process mixes is that of the air band.
The air band is a range that loosely lies between 4 kHz - 20 kHz. This is the area of the spectrum that displays detail and clarity for the top end of many sounds. I find that using shelves to boost the air band range yields far better results than using peaking bell shaped filters. However, you can make the bell filters work for you instead of against you as there are frequencies that are in the upper frequency spectrum that we cannot hear so using a shelf to boost this particular area yields no usable results.
The first process with any equalisation task is to perform what we term as corrective equalisation.
Corrective or Compensatory eq
Actually the first ever instances of equalisation was in the communications industry. EQ was used to counteract some of the problems in telephone systems. It then transgressed into the broadcasting industry.
Tone controls were created and used to compensate technical inaccuracies in the recording chain, more notably, compensating for microphone colouration and room acoustics. EQ was used as a means of controlling the gain of a range of frequencies.
This form of equalisation is termed as ‘corrective or compensatory’ EQ.
We use the same principles when using equalisation to remove problematic or redundant frequencies and the filter type we use to perform corrective processing on any sound is band-pass equalisation.
I always start by inserting hi pass and low pass filters at either end of the spectrum. In effect I am using band-pass filtering/equalisation.
A filter that passes frequencies between two limits is known as a band-pass filter.
A band-pass filter attenuates frequencies below and above the cut-off and leaves the frequencies at the cut-off. It is, in effect, a low-pass and a hi-pass together. The cool thing about this filter is that you can eliminate the lower and higher frequencies and be left with a band of frequencies that you can then process without the worry of redundant frequencies creeping up on you and summing gains and tripping compressors.
A filter that adjusts the levels of frequencies between a pair of values is known as a peaking filter.
Once I have the two filters in place I start to move them around until I have cut all the frequencies not needed.
Once we have tidied up the frequency spectrum of the sound we can start to work on the air band.
In the video I explain what a band pass filter is, how it works and how best to use it for cleaning audio channels. I show you the industry techniques we use to clean any piece of audio fast and effectively. I explain how to process the air band using different types of filters and demonstrate the process using a mix example.
Plugins used in this video:
FabFilter Pro Q2
Nugen Mastercheck Pro
Topics covered in this video are:
Equalisation techniques to master the Air Band
What is the Air Band
Filters and Processing
Using Metering for Referencing
Slopes and Responses
Dynamic and Static
Linear Phase versus Minimum Phase