Audio mastering basics

Audio mastering basics for your home studio

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Post production audio mastering is best done by an experienced professional – but iZotope’s guide will help you understand the basics as you experiment with mastering in your home studio.

This post on audio mastering is excerpted and adapted from Mastering with Ozone: 2015 Edition, a guide produced by our friends at iZotope. Reprinted with permission.

It is inadvisable to try to perform mixing and mastering in one step – that is, trying to master while simultaneously mixing a multi-track project. When trying to achieve both at once, you’re tempted to try to mix, master, arrange, and maybe even re-record within the same session. The separation of recording, mixing and mastering is very important. When mastering, you primarily focus on the overall sound of the mix and improving that, instead of thinking “I wonder how that synth part would sound with a different patch?”

If you focus too much of your work on a single instrument in a complex arrangement, you likely will miss the fact that even if you have improved the sound of that one instrument, everything else may have been impacted negatively. Get the mix you want, mix down to a stereo file, and then perform mastering as a separate last step.

An essential part of learning to master is to practice by mastering the work of others. It gives you good practice to listen to a wide variety of balances, tones, and dynamic range. Every engineer and producer has their own take on these things. A mastering engineer’s job is to try and get the vision of the engineer and producer (and ultimately the artist) to speak as clearly as possible. Once you have some experience experimenting with what sort of changes work or don’t work, you can do a better job of stepping back and evaluating your own projects with a slightly more objective ear.

However, even seasoned engineers prefer to have someone else master their work, as they value the fresh perspectives that outsiders bring.

Mastering effects

When mastering, you’re typically working with a limited set of specific processors.

Compressors, limiters, and expanders are used to adjust the dynamics of a mix. For adjusting the dynamics of specific frequencies or instruments (such as controlling bass or de-essing vocals) a multi-band dynamic processor might be required. A single-band compressor simply applies any changes to the entire range of frequencies in the mix. Equalizers are used to shape the tonal balance.

Equalizers are used to shape the tonal balance.

Stereo Imaging can adjust the perceived width and image of the sound field.
Harmonic Exciters can add an edge or “sparkle” to the mix.Limiters/Maximizers can increase the overall level of the sound by limiting the peaks to prevent clipping.

Dither provides the ability to convert higher word-length recordings (e.g. 24 or 32 bit) to lower bit depths (e.g. 16 bit for CD) while maintaining dynamic range and minimizing quantization distortion.

audio masteringWith all these types of effects, you might wonder where to start. First off, remember, just because you have all these modules doesn’t require that you use them all. Only use as many as you need. In truth, there really isn’t any single “correct” order for effects when mastering, and you should feel free to experiment.My preferred order usually is:

  1. Equalizer*
  2. Dynamics
  3. Post Equalizer
  4. Harmonic Exciter*
  5. Stereo Imaging*
  6. Loudness Maximizer

*I use these processors less frequently.

While you should educate yourself about the function of individual tools in your toolbox, ultimately the tools themselves do not make the sound. They are designed to help the sound, so you’ll want to decide what sort of help the sound needs. If there is something that comes close to being an iron-clad rule, it is that when you’re using the Loudness Maximizer and Dither, they should be placed last in the chain.

The fact is that nowadays we have digital signal processing (DSP) tools that are vastly powerful and allow you to change, twist, repair, and contort your sound a million different ways. It is also true that the more involved the processing, the greater the potential for harming the original sound. A multi-band tool will do much more “damage” than a single-band tool. A Mid/Side process will create problems that a standard stereo processor will not. Be careful! Before deciding you need the latest whiz-bang feature, figure out what the goal is. Then you can decide which tool is best to use.

Mastering tips

1. Have someone else master your mixes for you! In many project studios, the same person is often the performer, producer, mixer, and mastering engineer. If you have the tendency to add too much bass or not enough top end due to your listening environment, those tendencies will be compounded in the mastering. It’s common for the mix engineer to be too close to their own music. You’ll focus on some things other listeners won’t hear, and you’ll miss things that everyone else does hear. [The SoundLab at Disc Makers is an affordable, professional option for your mastering needs.]

2. Take breaks and listen to other CDs in between sessions. Refresh your ears in terms of what other CDs sound like. Even seasoned pros, who instinctively know what sound they’re working towards, will take a moment to listen to a familiar recording and recalibrate themselves during a session.

3. Listen on other speakers and systems. Burn a few different tracks to a CD player and play them on your home stereo system, or drive around and listen to it in your car. Don’t obsess over the specific differences; just remind yourself what other systems sound like.

4. Check how it sounds in mono. This can’t be stressed enough. A good ratio between mono (correlated) and stereo (uncorrelated) information is very important in many contexts; broadcast, LP/vinyl cutting, and even MP3 creation. When you listen in mono and important instruments vanish, or if the level drops significantly, you might need to rethink what you are doing.

5. Monitor at around 85dB SPL (C-weighted). How loud is that? Turn up your speakers until you can still have a conversation with someone who is a meter away without having to strain your voice. That’s just about right. When you listen at low to medium volumes, you tend to hear more midrange (where the ear is most sensitive) and less of the lows and highs. This is related to something called the Fletcher-Munson effect, which involves how different frequencies are heard differently depending on the playback volume. So check from time to time how it sounds at different volume levels.

6. Take a break. When you think you’re done, go to bed, and listen again the next morning.

The 2015 Edition of Mastering with Ozone was revised by Jonathan Wyner, iZotope’s Education Director. Jonathan is the Chief Mastering Engineer and founder of M Works Mastering Studios (m-works.com) in Cambridge, Massachusetts. Over the past 25 years, Jonathan has mastered more than 5,000 CDs, with notable credits include Aerosmith, David Bowie, Cream, Aimee Mann, Rahsaan Roland Kirk, Nirvana, and many more. In addition to his mastering projects, Jonathan regularly opens eyes and ears to the art of mastering as a faculty member at Berklee College of Music.

Download your free PDF of Mastering with Ozone. Learn more about iZotope at iZotope.com.

Learn How to Make a Great Master

Read More
Audio mastering – the mysterious post-production art form
Dithering – adding “good noise” to improve your home recordings
Your home studio mix – recording tips for better results
Ear Fatigue and Mixing Music – Know the Signs, Avoid Mistakes
Home studio posts – recording tips for producers, engineers, and musicians
Are your home studio acoustics killing your mix?

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9 thoughts on “Audio mastering basics for your home studio

  1. Great article except for one point is misleading. The part about listening in mono is not really a mastering thing. This should be done in the mixing stage to insure there is no detrimental phase cancelation (and to make correct eq decisions). If you are finding it in the mastering stage it is already too late. The exception being if you are using a poorly made eq. Use a linear phase eq for best results. Or better yet come see us at Virgin Sonic Studio and let us take care of it for you!

    Luke
    Virgin Sonic Studio
    VirginSonic.com

  2. Robert, excellent point.
    Bob Katz recommends to calibrate each monitor at 77dB (83dB really, but he then suggests to listen at -6dB when working on pop music). I tried to do that in my room, and I found even that a bit too loud to listen comfortably for extended periods of time.

    1. I also have been reading Bob Katz.
      So I got a sound meter and tried to set up my monitors.
      83-85 db is quite loud.
      But knowing where it is and how you get there can uncover other things.
      Like gain staging the monitor environment.
      What I saw was that I was turning my DAW’s physical volume control too low, and running my mix too hot.

    1. Nooo! Listening to the low end loudly compounds the ring mode and standing wave problems in your room (You would be EQing the room and not your mix). You should be able to carry on a normal conversation at normal levels and be heard clearly over your mixing volume. The best thing you can do to make correct eq decisions it listen in mono and see what instruments and frequencies are fighting each other.

      Luke
      Virgin Sonic Studios
      VirginSonic.com

  3. Regarding monitoring at around 85dB SPL (C weighted): you really need to specify this with more precision. I would assume that for this to mean anything with music, you would need it to be a slow (average) reading on an SPL meter, rather than a peak reading.

    This gets us into the whole issue of how you calibrate a monitor system for a given level. The ATSC (Advanced Television Systems Commitee) for example, recommends that a special mid-range only pink noise signal that measures -20 dB relative to digital full scale be used, and that the calibration level should vary depending on the room size. Only large rooms like theaters should use the 85db SPL level–small rooms, such as one finds in domestic settings should use levels as low as 76dB SPL. This is due to the fact that in small rooms, with their close reflections from the nearby walls, measured levels that would sound good in a large room are subjectively too loud. Of course, this a broadcast standard, and may not be stricktly relevant to general music mastering, but it gives one some idea of the issues involved with monitor calibration levels.

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