Mastering Guide for Streaming Platforms: Balancing Equalisation and More
Mastering Guide for Streaming Platforms: Balancing Equalisation and More
Equalisation (EQ) is a fundamental phase of mastering, allowing tonal problems to be corrected, frequency balance to be enhanced and the mix to be prepared for subsequent dynamic treatments. This process does not just 'improve the sound', but is an essential technical tool to ensure that the final product is coherent, musical and translatable on any listening system.
In mastering, the order of operations is crucial: equalisation almost always precedes compressionas intervening on the frequencies before treating the dynamics ensures a more controlled and effective result.
Why Equalisation is Crucial in Mastering
Equalisation in mastering meets the following three basic requirements.
Tonal Correction
It serves to eliminate resonances, annoying frequencies or inhomogeneities. These problems are often caused by the acoustics of the mixing room or the non-linearity of the monitors used, but sometimes also by the hasty or ill-considered choices of the sound engineer.
Appropriate correction allows the mix to be 'cleaned' of these frequencies and compensate for deficiencies.
Tonal emphasisation
It allows the tonal characteristics of a song to be enhanced, emphasising key frequencies that improve overall perception.
For example:
- Increased presence in the mid and mid-high frequencies (400-3000 hz) to improve intelligibility of solo sources
- Better definition in the treble, wide-band to increase brilliance without creating harshness.
- Better bass definition, wide bandwidth, to increase depth without creating boxiness in the mid-bass or problematic swells in the deeper bass.
Preparation for Dynamic Treatment
A well-balanced tonal base prevents problematic frequencies from activating compressors or limiters excessively. This results in a more natural, effective and less invasive compression, giving the sound engineer a more relaxed mode of operation.
Why Equalise Before Compressing
Equalisation almost always precedes dynamic treatment for three key reasons.
Removal of unwanted frequencies
Problematic frequencies or frequency ranges, as well as being annoying, especially during loud listening, can overload the compressors, leading to undesirable results.
Attenuating them before compression helps to maintain a cleaner, more compact sound.
Controlled Emphasis
The deficient frequency bands should be increased before compression to ensure a more even balance of the audible spectrum.
Efficiency of Dynamic Treatment
A tonally well-balanced audio signal allows the compressor to work more transparently, without emphasising unwanted elements.
Equalisation Techniques in Mastering
Corrective equalisation
It uses bell-shaped filters with Tight Q to reduce resonances or problematic frequencies without affecting the surrounding areas of the spectrum.
General Tonal Equalisation
It uses bell-shaped filters with Wider Q to change the overall balance of the mix. It is ideal for emphasising or attenuating groups of frequencies without creating noticeable imbalances.
Equalisation Shelving
It employs shelving filters to evenly handle the entire range of low (typically below 100 Hz) or high frequencies (typically above 5 or 10 kHz), making the sound more open, airy and bright.
High-pass and low-pass filters
Applying a high-pass filter above 20 kHz helps reduce aliasing and other artefacts.
A low-pass filter below 20 Hz (or even higher, if the harmonic content of the song is not affected) is useful to eliminate unnecessary subsonic frequencies.
Practical Considerations on Equalisation
Moderation in Interventions
EQ in mastering requires very precise interventions of only a few dB.
Drastic changes are only permissible on very unbalanced mixes; in such cases, however, it is often preferable to carry out a review of the mix.
Critical Listening
Testing the master on different playback systems (monitors, headphones, consumer speakers) ensures that the changes are consistent in various contexts. However, the final judgement must be based on listening in a perfectly linear system.
Use of Measuring Instruments
Spectrum analysers and loudness meters help identify problematic frequencies and balance the signal objectively.
Increased bass perception
In less purist musical genres, such as pop, where the bass has an important strategic function (think hip-hop, for example), instead of overloading the master, it may be advisable to create high harmonics that, due to the harmonic composition, psycho-acoustically suggest to the ear the presence of the lower frequencies (otherwise hardly or not at all audible in telephones and other small devices).
To achieve the above, you can use special plugins, or do the following:
- duplicate the track of the bass, kick and any other instruments with a significant extension below 80 Hz
- convert track content to upper octave
- with an LPF filter (with an average decay curve, e.g. 12 db oct) limit all the higher harmonics of the new track, preserving total audibility at the fundamental frequency (which is an octave above that of the original track, of course)
- mix the new track to the original in the desired proportion (test listening both in the studio monitors and with a smartphone)
- act on the LPF filter above to adjust the overall timbre, changing the frequency cut-off and slope as desired, until the most satisfactory timbre is obtained
- possibly equalise and then compress the generated track or the ensemble of the two tracks together (original and generated combined in a group) to obtain the best timbre and perception in each listening device
Advanced Tips for EQ in Mastering
Spectrum Balancing
In modern genres (pop, rock, EDM), the entire audible spectrum (20 Hz - 20 kHz) should be represented with a linear curve slightly inclined towards the high frequencies. Gradual decline below 60 Hz and above 14 kHz.
Interventions on Acoustic Genres
For more rarefied genres (e.g. chamber music, acoustic jazz), the spectrum could be limited to between 80 Hz and 10 kHz. Do not accentuate unnecessary bands or bands with no musical content.
Band Peak Management
In the presence of peaks (e.g. around 12-15 kHz or 80-120 Hz), distributing the content over adjacent bands can avoid perceived imbalances.
High-Cut Filter:
Always apply a filter above 20 kHz to limit aliasing, which is useful to ensure flawless reproduction.
Stages of Conscious Mastering
Precise Mix
Exporting already tonally balanced mixes reduces the need for drastic interventions during the mastering phase and produces better results.
It is advisable to export the mixes, ready for mastering, at exactly twice the sampling rate of the mix project.
Uniformity between Tracks
In an album, align tracks on a new session to evenly balance their volume, tonal colour and, subsequently, dynamics.
Mastering Chain
Equalisation is the first link, followed by compression to achieve dynamic coherence and uniform tone.
Conclusion
Equalisation in mastering is a crucial technical and creative phase. Intervening in a measured manner ensures a balanced, dynamic and translatable end result on any platform and device. A well-executed mastering preserves the integrity of the original mix while improving the overall sound quality.
Dynamics in mastering
See also this other blog article
Mastering Guide for Streaming Platforms: Normalisation, LUFS and Loudness
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