Guide to Mastering in Izotope Ozone

Izotope have a fantastic range of products – all reasonable priced and extremely user-friendly to any home studio owner. Amongst the products is the Ozone suite of mastering plug-ins, which can be used individually in a mix, or in a chain as part of the mastering process. In this article we will look at each module in turn and provide some useful information for those who are new to mastering.

Before we get in-depth with mastering using the Ozone suite of plug-ins, let’s talk a little bit first about the purpose of mastering and how it differs from mixing, and how (unless we have an expensive mastering room with great gear!) we are more likely “maximizing” our music than actually mastering. Maximizing, in our case, refers to setting the volume level and improving the quality of our music with the tools we have on hand.

This is an important distinction to make as our own music quality is limited to the room and gear (plug-ins) we have available. Ozone provides, in my opinion, the best home studio solution for mastering. So despite our room quality, we can still adequately improve the quality of productions.

So, what is the purpose of mastering? If we think about the journey the composition takes, it may look a little like this:

  1. Thought - the composer’s initial idea (the development of an idea from a single song concept, or lyric, or melody line.)
  2. Idea - the development of the thoughts to song composition.
  3. Composition - the intro, outro, verse, chorus, lyrics, and melodies.
  4. Recording - all the tracks that will finally make up the song parts (vocals, drums, guitars, keys).
  5. Mixing - getting the recordings to sit comfortably with each other. Developing the emotion of the song.
  6. Mastering - improving the song to the best of our ability, with the tools we have at our disposal.

As you can see, each step from 1 to 6, develops a song from a thought in the composer’s head to a “product” that can be enjoyed by anyone willing to listen to it.

In each of the six steps, an improvement is made. When the independent thoughts are put together to form an idea, an improvement is made - and as a consequence, or side-effect we move one step closer to being able to communicate the emotions of the composer (the thoughts) to the audience (the person who listens to the final product).

Fine Tuned Emotions

The bulk of the improvements are made in the mixing stages. So, step six, mastering is the final step where improvements will be made, and the emotion is “fine-tuned.” We are lucky enough to have access to the Ozone mastering plug-in suite to assist with the last step.

But just remember that the Ozone tools shouldn’t be wielded to remove intent from the original ideas of the music - we want to fine-tune the emotion by rebalancing and improving the tone “subtly” (or sometimes not at all), and increase the loudness for commercial release without ruining the song dynamics.

For a full explanation of the difference between mixing and mastering read the article here. Pay particular attention to the fact that true masters need specialized rooms, something that the average home studio owner does not have access to.

Mastering with Ozone

Session Set up

A great tip for setting up your session is to use three stereo tracks. These are:

  • Source Track - containing the music you want to master.
  • An Auxiliary Track - where all the processing will be done.
  • A Recordable Bounced Track - which you will use to export the mastered WAV or MP3 files.

Headroom

Use the K-12 system for mastering. If you have followed advice elsewhere on this site, you will have recorded and mixed using the K-20 system. In any case, the K-12 system provides a suitable amount of headroom for mastering and will help to ensure your songs have enough dynamic range, while still being “loud” enough.

The Interface

Ozone Interface

Figure 1: Ozone Interface

The suite of Ozone plug-ins all share the following features:

  1. Preset Browsing
  2. Undo and History
  3. Options
  4. Help
  5. Bypass
  6. and the next meter layout:

  7. Input Meters (LHS) and Faders
  8. Output Meters (RHS) and Faders
  9. +/- Scaling
  10. Lock / Unlock
  11. Mid / Side Monitoring

1. Preset Browsing: Ozone has provided presets for each module type. They are not intended as immediate fixes for any particular situation, and therefore should be used as a starting point for your own sessions. Presets are useful for scanning through to understand the effect, and power, each plug-in.

2. Undo and History: Use this button to undo the last move. Use the undo in conjunction with the history list your moves back one by one. The history pop up window also provides the opportunity to clear everything or “remember” a rollback location to help A/B a set of moves (there are four memory settings available).

3. Options: The options pop up provides access to the general, spectrum, and I/O settings for the module. On some modules, there are a specific set of controls. In most cases, the default options are adequate for first-time users, but feel free to dive into more details when you can spare the time.

4. Help: Use the help button to get direct access to each modules reference material.

5. Bypass: Use the bypass button to switch the module in and out during your session. You will notice an “ear” icon to the right of the bypass. This is for “automatic gain matching.” This feature will match the output levels of the bypass the number bypass audio and is therefore very useful when A/B-ing.

If you already understand the importance of listening and comparing to audio signals at the same (equal) volume, that’s great! If not, check out the article here on the Fletcher Munson curves and why they are essential for all home studio owners.

6. Input Meters and Faders: The two faders on the left-hand side provide visual feedback for the input signal to the plug-in. Changing the input gain can affect the amount of processing done to the signal, so be careful to recheck your work if you adjust this during the mastering phase.

7. Output Meters: Shown on the far right of the interface these meters provide visual feedback for the processed signal leaving the plug-in.

8. +/- Scaling: In their default state the meters are calibrated between -inf, -50 dB, and 0 dB. Use the +/- button to “zoom” in and out on the upper range of the scale. Pressing the plus button twice will change the scale to -inf, -30 dB, and 0 dB.

9. Lock / Unlock: With the icon in lock mode the meter faders will move as a pair - sliding one up by 5 dB will also slide the other up by 5 dB. In unlock mode, however, the two faders will move independently of each other. For example, right and left, or mid and side channels can be adjusted separately.

10. Mid-Side: this icon, which looks a little like half of the Olympics flag, switches between R/L and M/S channel manipulation. When pressed, the icon lights up and is greyed out when in standard (R/L) mode.

M/S is a powerful tool in mastering and is worth spending some time to understand. If you are not familiar with M/S stick to R/L for now, you can still get great results.

Great! Now that we are familiar with the interface, let’s dig into the modules. The modules we are going to look at are:

  • Ozone Equaliser
  • Ozone Exciter
  • Ozone Imager
  • Ozone Dynamics
  • Ozone Maximiser
  • Ozone Dither

So, let’s get started!

The Ozone Equaliser

This high-quality EQ provides eight bands of filtering. Each can be switched in and out using the tab menu under the graphic display. The EQ can be set to analog or digital mode using the icons to the left.

Each filter provides the option to choose high-pass, low shelf, bell, high shelf, and low-pass. And within each option the choice between flat, resonant and brickwall for the high-pass and low-pass. Analog, vintage, Baxandall, and resonant for the low and high shelf. Peak, proportional Q, and band shelf for the bell. The vintage filter is based on a Pultec design.

The high-pass and low-pass slope (dB/octave) are adjusted on the right side of the tab menu or by grabbing the sliders on the graphical display. Slopes can be set to 12 dB/Octave, 24 dB/Octave, or 48 dB/Octave. Gentle slopes are advised for mastering.

Qs

The Q for the shelf and bell filters is also adjusted on the right side or by grabbing the slider. Qs can be adjusted from 0.2 to 12 or 24 dB/Octave.

The frequency can be adjusted by dragging the graph point for the frequency value itself (on the tab menu). Move the mouse up and down, or side to side to adjust the amount. Alternatively, after double-clicking the value, you can type in the frequency directly.

Gain

The gain adjustment works in a very similar way to the frequency. To reset frequency and gain to the default position simply double-click the band’s ID number and the graphical display.

In digital mode, the linear phase response can be adjusted with the bar located under the Q slider. And “surgical mode” can be selected. The digital EQ mode is a very “transparent” EQ but needs a little more processing power.

Graphical Window Right Click

Right-clicking the EQ window will provide the option to either select “EQ Options” or “Spectrum Options.” Each is a shortcut to the options tab (which you can get to through the tab menu).

The EQ options provide the ability to show “Music Units” - in particular, the sea note for each Octave (C1 to C8). And to show extra curves with the ability to look at “Phase Delay,” “Phase Response,” and “Group Delay.”

The spectrum option allows the graphical display to be altered. Some of the more useful features are “Fill Spectrum” which graze in the area under the frequency, “Show Peak Hold,” and the spectrum type which can be changed from linear to 1/3 octave, critical, and full octave - all useful in their own way.

Reset any of the options any time with the reset button.

M/S Processing

We talked earlier about the powerful M/S monitoring on every Ozone module; however, the EQ, Exciter, Imager, and Dynamics modules also allow M/S processing.

Also, the EQ provides the ability to process the left and right channel separately. This is usually necessary, not recommended, and reserved for expert use for fixing a particular problem with an unbalanced mix. I’m assuming you will be mastering your own mixes, so the advice here is to fix any unbalanced channels in the mix and not in the mastering session.

The M/S mode allows you to solo and bypass channels, as well as link the two channels together with the chain switch. As mentioned earlier, M/S mode is very powerful and needs a little time invested in studying its benefits before jumping straight in. Feel free to experiment as this is often an excellent way to learn the basics quickly.

EQ Matching

The last thing we are going to discuss for this module is the EQ matching feature. This feature is useful for referencing your own music’s tone to that of another track. From my personal experience, it really helped to gain an understanding of how the low end compared, but it is also useful for full frequency comparison.

To use the matching feature, you will need to import a reference track into your mastering session and run the audio through the EQ. Then record the frequency profile into the plug-in, save it, and apply that EQ profile to your own audio.

The feature provides the ability to smooth the curve (smoother is recommended) and adjust the amount that the target audio is processed. For example, you may only want to apply 10% of the reference EQ to your target audio. Mastering generally requires broad EQ moves rather than narrow cuts or boosts like you may have to do in mixing.

The Ozone Exciter

The first thing that you will notice about this module compared to the EQ is that the graphical display has a four-band crossover network. The band's crossover points can be adjusted in each band can be bypassed or removed (down to a single full frequency band).

Each band is controlled via the “amount” and “mix” sliders on the lower section of the module in each band can be put into solo mode.

The module has six excitation programs:

  1. Warm - even harmonics with fast delay.
  2. Retro - odd harmonics with slow delay - mimicking the excitation of a transformer.
  3. Tape - odd harmonics with tape saturation.
  4. Tube - tonal harmonics that emphasize transience.
  5. Triode - subtle warm tones modeled on tube circuits.
  6. Dual Triode - warmer tones also modeled on tube circuits.

The oversampling can be switched on and off. When turned on, oversampling is applied, which improves quality but does require more processing power.

In the bottom right of the crossover, window sits the “learn” feature. Pushing “learn” while audio is playing will force the module to automatically adjust the crossover points - using Ozone’s algorithm - to fit the frequency balance. This is a useful feature for beginners, or for finding a good starting point.

Ozone Exciter and Imager

Figure 2: Ozone Exciter and Imager

The Ozone Imager

Like many of the other mastering plug-ins in the Ozone range, this module is multiband. This means that the stereo width of each band can be affected individually, providing a powerful tool to widen and narrow your audio.

The multiband window also provides the solo, bypass, and learn functions that were discussed in the Exciter description.

This module, in particular, has some great presets available through the browse feature. Try playing some audio and toggle through each of the precepts. Note the contrast between “Tight Low End,” and the “Modern Width” settings. Be sure to check out the differences using a pair of headphones too. Very cool stuff!

Features and Controls

The Imager module has fewer “controls” than the other modules but has a few more visualization features. Starting in the top left of the module you will notice the three icons for Crossover View (default), Stereo Width Spectrum, and Correlation Trace. The Vector Scope is displayed bottom right and can be switched between Polar Sample, Polar Level, and.

The Stereo Width Spectrum shows a visualized version of the amount of stereo width in the frequency range. A flat line indicates an entirely mono signal.

Correlation Trace

The Correlation Trace shows a real-time moving trace of the stereo correlation. Traces above the line shown in blue indicate a positive relationship, white below the line, and in red indicates a negative one. To avoid mono compatibility and phase issues try to keep the correlating trace in the blue zone (positive). Too much negative correlation will cause mono folded audio to “disappear.”

Note: the correlation amount is also shown on the right side of the Vectorscope (labeled -1, 0, +1) as an instantaneous amount.

The Polar Sample Vectorscope uses a dot-scatter plot to help visualize stereo width.

Polar Level Vectorscope

The Polar Level Vectorscope uses solid outlines to represent instantaneous average values, and solid grade internal graphics to indicate the historical (just past) signal. The solid contours represent the magnitude and direction of stereo signals and represent the left, center, and right components of the stereo image.

Lissajous

The Lissajous Vectorscope (or Liss) mimics the behavior of a hardware oscilloscope. This type of monitoring indicates mono components by a vertical pattern, and the difference in signals, by a horizontal pattern. Generally, the pattern should neither be too tall and slim, or too wide and narrow.

To make audio appear “wider,” we are manipulating the phase of one or both sides of the stereo signal. Audio that is precisely the same on both channels is mono. Audio that is different, even slightly, is stereo.

Manipulation of each band can be controlled with the sliders (bottom left). Pulling the slider entirely to the bottom makes a signal 100% mono while pushing the slider up “widens” the frequency band.

Center The Lows

One thing to bear in mind when mastering the low end of the mix is that “low end” instruments “should be” (but not always!) centered in the final production. Therefore be careful not to widen the lower bands so much as to destroy the intention of the “mix.” As with most mastering processes, subtle enhancements work better than aggressive ones!

The final feature we are going to discuss in this module is the “StereoIze.” The StereoIze is useful for livening up a mono or narrow mix. It adds synthetic components the audio that provides a natural-sounding width.

Listen to the transformation of the mono recording through a pair of headphones - fantastic stuff!

The Ozone Dynamics Module

The combination of expansion, compression, limiting, and input detection circuit and mid-side processing make the dynamics module one of the most powerful of the Ozone suite. This module alone can turn any average mix into something wholly spectacular.

The Ozone team provides another mastering module with multiband capability. And if you have read the section on the EQ module, you will also understand the benefit provided by the mid-side functioning in the dynamics module too.

Ozone Dynamics Module

Figure 3: The Ozone Dynamics Module

By selecting each band and the graphics window, you can choose the controls for each band. Note that the band is “greyed-in” for the selected band and that each has a unique number and color (purple, blue, yellow, red).

Features

So let’s get started explaining the features of this dynamics processor. The first thing to notice about the module is that the plug-in layout is split into four columns.

The far left column provides access to the threshold for compression and limiting. At the base of the column, you can choose between Peak, Envelope, and RMS detection circuits.

The next column provides controls to limit a compressor. Both have independent ratio, attack, release, and knee controls. Just remember not to be too aggressive with a gain reduction from compression during mastering, and that there is another stand-alone limiter and dither module which can be used on the final insert of the mastering chain.

For more information about how to use a compressor, see the article here.

Next, on the right, controls for parallel compression (at the top) and the graphical display of all (most!) of the settings. The parallel slider allows you to choose between 100% right and 100% wet. The graphical display allows you to control some of the settings directly.

When you hover your mouse over the display notice how the plus and minus buttons appear. Uses buttons to zoom in and out of the processing area.

Note: double-clicking any valuable slider will set it back to its default position.

In the right-hand column, you can select between independent mode and global mode. The global mode is useful for a side-by-side view of all of the band settings and processing.

Use the slider and the independent/global icons to adjust the make-up gain or set the adaptive release or auto make-up gain settings.

Side-Chain

Finally (in the top left) the module provides access to the input filter (read “side-chain” filter) which can be set to high-pass, tilt, or slope modes. You can also listen to the side-chain signal using the solo button.

In this area, you can also switch to the gain reduction trace window, which provides a visualization of real-time gain reduction processing.

The Ozone Maximizer

For the last piece of the puzzle for any mastering task is the maximizing processor. It’s time for all the hard work, creative energy, and perfection to be maximized for commercial release.

Ozone Maximizer Module

Figure 4: The Ozone Maximizer Module

The Ozone module provides maximizing in the form of three intelligent peak limiters and one tube-based. In addition, dithering can be applied to the final audio file. Dithering is beyond the scope of this article but is nonetheless an important process to carry out if you are producing digital files.

Intelligent Peak Limiting

Ozone has its own algorithms for intelligent peak limiting in the forms of IRC1, IRC2, and IRC3. Each of the three versions has its own character and increases in DSP usage with higher numbers. The IRC3 as an additional option of Pumping, Balanced, Crisp, and Clipping. Stick to Balanced if you are new to the module and experiment with other settings when you can hear the subtle differences.

The tube setting is modeled on an analog brick wall feedback limiter (Ozone modelled this on a Fairchild 670). Again, stick to the Balanced mode until you get a feel for the module.

The limiter has the standard controls: Ceiling (set to -0.3 dB if you are not sure what it does) and Threshold. The threshold can be adjusted downwards to increase the volume of the audio. Switch the True Peak Limiting button on for ensuring that loud masters do not distort when they get into the real world of digital to analog converters. The true peak limiting is your guarantee that music released will not distort.

Character

The character of the limiting can be controlled with the vertical slider. Choose between slow, transparent, smooth, and fast. The IRC character can be related (roughly anyway!) to the genre of music being mastered. As a guide is a slow character for slow music and the fast character for aggressive music.

The IRC modes also allow further manipulation through the stereo link and transient emphasis. The stereo link enables dual style (left and right) limiting on each channel. The transient emphasis is useful for preserving the attack of instruments like drums while still being able to increase the perceived loudness.

The Ozone Dithering Module

without getting too technical it is probably useful to explain something about dithering before getting into its application through the Ozone Maximiser.

Ozone Dithering Module

Figure 5: The Ozone Dithering Module

As digital audio is recorded, processed, and reproduced at different bit rates, gaps are created between samples that need to be filled with low-level digital noise. Without dither, sounds can distort and add errors in the digital file.

The dithering process is always the last in the mastering chain and should only ever be done once.

I am going to keep this module explanation brief as it gets very technical very quickly. If you really want to learn more about dithering you can check out Ozone module help files (use the “?” Help button next to options), look online for more info (Ozone Dithering Guide), or look into Bob Katz’s book (on my recommended reading list).

Whenever I use this module I keep the default settings:

  1. 16 (CD) bit depth
  2. Auto Banking (off)
  3. Medium Dither Amount
  4. MBIT+ Dither Noise Shaping (higher)
  5. Filter DC Offset (off)

Remember that the dither module is completely separated from the maximizer module and is the last process to be applied. I hope that you become familiar enough now with this set of mastering plug-ins - have fun with them and good luck with your mastering endeavors.

In this article, we have talked about mastering one song in isolation, but of course, this is not always the case. Mastering is also used for providing continuity between songs. For example, if the songs are a part of an album, or if the songs need to sound the same for a particular artist.