Before sending in music for audio mastering, it is crucial to get the clearest, best sounding mix possible. Focusing on the frequency spectrum will get better tones from each instrument and ultimately lead to a great sounding mix. The primary goals when equalizing are to make the instruments sound full, add clarity, and make the instruments fit in their own frequency range. There are 6 major frequency ranges that are known as the magic frequencies.
Sub-Bass- between 16Hz and 60Hz
This area is the low end that provides more of a bassy feeling as opposed to bass that is actually heard. These frequencies add a sense of power to the song. Be aware that too much emphasis will make the song sound muddy.
Bass- between 60Hz and 250Hz
This is the fundamental rhythmic section of the bass frequencies. Adding too much or too little of this area will affect the thinness or fatness of the low tones. These frequencies are where the boomy sound comes from.
Low Mids- between 250Hz and 2000 Hz
This is the range that the lower tones of musical instruments lie. Boosting this area can provide the telephone-like effect or tinny tone. Within this range lies the “devil frequency” of 300Hz. This area is notorious for adding muddiness to a mix.
High Mids- between 2kHz and 4kHz
A lot of the vocal qualities can be found in this part of the spectrum. If boosted too much, a lot of the speech elements are covered up and made indistinguishable. In a lot of music it is important for the vocals to be clear and stand out. A helpful trick is to dip this area in other instruments, and adding a few dB on the vocals. This will maintain the power and volume of the instruments while keeping a nice level for the vocals without sacrificing clarity.
Presence- between 4kHz and 6kHz
This is an important area for finding clarity and definition for instruments and vocals. These frequencies affect the distance of the sounds for the listener which are crucial for getting the in your face vocals that a lot of listeners are looking for.
Brilliance- between 6kHz and 16kHz
This area controls clarity and brilliance. A lot of the sibilance from vocals are found here as well as cymbals. This frequency can be harsh if boosted too much and cause listener fatigue.
Its important to listen to the mix at a moderate level while you are making adjustments. After 30 minutes or so, take a break to let your ears rest. If you mix for an extended period of time without breaks, your ears will become exhausted and you will not be able to properly hear the adjustments being made. You could be doing more harm than good to the mix with tired ears.
While EQing it is a good rule of thumb to attenuate, or cut, the frequency first instead of boosting. Boosting is simply adding more volume which may make it stand out more and sound better when really the tone is not ideal. Boosting also causes some slight phase shifting which makes it difficult to fit the instrument in its own space in the spectrum. On the other hand, these are merely guidelines and whatever sounds best is the method to go with. By understanding where instruments lie in the spectrum, it is possible to get the clearest mix possible before the final polishing step of cd mastering is underway.