In equalization our goal is to find a tonal balance in the mix. In other words the overall sound has to be pleasant to our ears. Note that if you apply equalization the mix has to maintain its quality on every audio source you can imagine. If you boost the low-end to much it will sound dull on a lot of hi-fi systems in cars and living rooms. So be careful and only use it when necessary.
So equalization in audio mastering is all about the correction of the mix. The tonal balance should match that of a reference track. i.e. if you have to master a dance track you probably want to listen to a reference of the same genre. If you listen back and forth between an audio reference and the master you are working on you probably detect differences in the frequency balance. We can name these differences to make communication about audio easier. I’ve made a chart of the audible frequency spectrum with the different names which are given to a certain feel. i.e. the name “edgy” or “muddy”.
Look at the chart and notice that if you cut the frequencies from 4 to 8 kHz the edgy sound will disappear. If the mix sounds “nasal” you’ll probably want to cut frequencies from 600 to 1500 Hz. Note that ears are more sensitive for boosting than cutting. So always look for other possibilities. Also note that equalization is all about yin and yang. If you work on the high-end of a mix it will interact with the low-and and vice versa.
Rest your ears – audio mastering takes time
The following is very important. You’ll need your ears to rest. After working on a master too long you’ll not hear the changes correctly. Listen to the master the next day and apply small changes. A mastering engineer is good if he (or she) takes his time to finish the product.
Guidelines for equalization
- Offending frequencies can be notched out.
- Boost using gentle slopes / wide bandwidths
- Horny sounds lie between 800 and 2000 Hz
- 3 to 4 kHz will bring up clarity and presence of vocals. It is not a good idea to boost in this area if there are distorted guitars in the mix.
- Muddiness lies between 200 to 400 Hz
- A shelve above 6 to 12 kHz will give sparkle and air
- Attenuating below 250 Hz will increase clarity and presence.
- Cutting or boosting more than 5 dB is not healthy. This means the mix is not good and it needs to be re-mixed.
- Use as few bands as possible, especially no neighboring frequencies.
- Try to work on the bass with a multi-band compressor rather that an equalizer. This will straightened up the low end of the mix.
- Don’t boost fundamental frequencies only. This would lead to an undefined frequency spectrum but try boosting harmonics instead.
These where some basic equalization tips for audio mastering. Now it’s time for our next part of this mastering tutorial. Harmonic excitation.