Audio Mastering Basics
Mastering scares a lot of people. Throughout history, professional mastering has always been an advanced skill that only the most experienced engineers would take up. The classic assumption is that you need perfectly trained ears and an expertly treated room to even attempt mastering.
Thanks to modern plugins and software, it’s perfectly possible to master music at home to a high standard. Although a track that is mastered outside of a professional mastering studio will never be as translatable or pristine as a properly mastered track, you can still get great results at home with the equipment you already have.
If you are producing an important album or single, I recommend sending your mixes off for professional mastering. But when you are on a budget, working with demo tracks or need a quick turnaround, home mastering is the ideal solution.
The Mastering Phases
You might think the term mastering only refers to the processing the final stereo file after the mix is finished, but this is a misconception. Mastering is much more than that. It is the process of finalising and album or EP. The mastering engineer is the last person to check everything over before printing it to CD and other formats.
It might even be your job to decide on the order of the tracks. The artist, producer or label probably have an idea in what order they want the tracks to appear, but when mastering an album you need to think about the flow of the tracks.
Consider if the album starts with a bang, or the track order builds to a crescendo. Order the in a way that is exciting. Songs with a similar key may appear next to each other to help the flow of the album. Give consideration to factors such as these.
Once a track order has been decided, it’s time to start processing the individual tracks. This generally involves six core phases: noise reduction, surgical equalisation, compression, tonal equalisation, limiting and dithering.
You’ll also need to ensure the sound is consistent between the tracks. If certain songs were recorded or mixed by different engineers, it’s your job to use equalisation and compression to make them sound more similar and cohesive.
Stereo File Processing
Looking at the processing phases in more detail, this is by no means a definitive order, and sometimes it works best to apply these processes in different stages. Nevertheless, this is the order that I use the most.
Noise reduction is especially important when re-mastering old analogue recordings. Hums, hisses, clicks and pops must all be removed from the track before it can be further processed. Dedicated noise removal tools such as iZotope RX 5 are perfect for this job.
Noise removal with RX 5
Surgical EQ can then be used to remove any nasty elements of the sound. Filters can also be used here to roll off any unnecessary bottom end (below 20-30Hz).
Applying surgical EQ with a Linear Phase EQ in Logic Pro X
Next, compression is used to squeeze some more volume out of the track. By adjusting the attack time it’s possible to add more punchiness (slow attack time) or thickness (fast attack time) to the sound.
Adjusting the release time can also add more apparent volume (fast release time) or make the compression sound more musical (slow release time). It’s not unusual to use several compressors in series, with each compressor applying 1-3dB of gain reduction.
Applying compression in Logic Pro X
You can use multiband compression if you want more control over the individual frequency ranges. For example, if you have been sent a track where the hi-hat is particularly loud, you could compress the frequency range of the hi-hat rather than just removing with EQ.
You can also use multiband compression to tighten up the low end of the mix without affecting the entire frequency spectrum.
Applying multiband compression with the Waves C6
Now that you’ve removed any nasty elements and compressed what is left, shape the sound of the track with EQ. If the mix is too bass heavy, or too bright, EQ can be applied to correct these issues.
The track needs to translate well onto as many systems as possible, so compromises are made to make sure the track will sound good anywhere. You could use any form of equaliser here.
Linear phase equalisers are great for mastering and are less likely to cause phase issues, but only when subtle changes are applied. Analogue EQs and plugins modelled on analogue EQs also work well here for adding character.
Adding warmth with a Pultec style EQ
A limiter is then used to increase the volume of the track. Again, several limiters can be used in series. Using a good limiter is a vital part of mastering. This is the phase when everything can quite easily go wrong and you can ruin the mix.
Be subtle with limiting, and always choose musicality over volume.
Applying a limiter in Logic Pro X
Finally, if you have been working at 24-bits, or higher, the track needs dithering down to 16-bit, ready for exporting.
Dithering should only be applied once at the very end of the mastering process. If you don’t dither your tracks, and simply export them as 16-bit, some distortion could occur. Applying downward bit conversion with dithering is an important final step.
Exporting and dithering in Logic Pro X
Of course, this is a very basic outline of the various mastering processes. There are many more tools and techniques that could be used, including stereo widening, mid/side processing and numerous other process. But, for the sake of this series, I’ll focus on those six key processes.
Home Mastering Equipment
All of these processes can be applied in the DAW, using stock or premium plugins. There are also numerous dedicated mastering plugins that cover every processing step.
The listening setup is the most important aspect here. Acoustic treatment will improve the sound of the room and make equalisation much easier. If possible, use absorptive panels at the first reflection points—where the sound from your speakers would bounce off the wall and into your ears—and use bass traps to control the low end in the room.
Use a professionally mastered reference track to help you with your decisions. Constantly compare your master to the reference. You can also check the tracks on headphones and other speakers systems to make sure they translate well.
In part two of this series on home mastering, I’ll explain dynamic processing in more depth. You can look over my shoulder as I apply gain staging, compression and limiting to a finished mix. Then, in part three, I’ll explain all about EQ and the other important processes.