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electronic MUSICIAN

iZotope Ozone 4 (Mac/Win) Review

By Michael Cooper | June 1, 2009

FIG. 1: Ozone''s Paragraphic Equalizer module in M-S mode shows the EQ curve for the mid and side channels in orange and blue, respectively. Note the analog-modeled highpass filters'' overshoot. The I/O meters are showing M-S levels here.

FIG. 1: Ozone''s Paragraphic Equalizer module in M-S mode shows the EQ curve for the mid and side channels in orange and blue, respectively. Note the analog-modeled highpass filters'' overshoot. The I/O meters are showing M-S levels here.

Ozone is widely regarded as the cost-effective stereo mastering solution for the masses. The software plug-in supports RTAS, AudioSuite, VST, MAS, Audio Units, and DirectX formats, and combines six independent processing modules: paragraphic equalizer, mastering reverb, loudness maximizer (with dithering), multiband dynamics, multiband harmonic exciter, and multiband stereo imaging.

Ozone 4 adds dozens of new features and workflow refinements to earlier versions. Additions include mid-side processing, parallel compression, new Maximizer and Exciter modes, automatic gain compensation, and a new Preset Manager with more than 50 new presets. You also get MacroFaders that adjust several parameters at once and a bevy of new meters.

Ozone features 64-bit processing throughout and incorporates both analog modeling and digital linear-phase algorithms. It supports sampling rates up to 192 kHz. I reviewed Ozone 4.03 as an Audio Units plug-in in Digital Performer 6.02, running in Mac OS 10.5.4 on an 8-core 2.8 GHz Mac Pro.

The Big Picture

Ozone opens with a view of its new, detachable Preset Manager, which organizes 140 factory presets inside folders according to music genres and various applications (for example, to use on individual instruments). Use a preset as a starting point for mastering or select the default setup to null all settings and start from scratch.

As you select each of Ozone's six modules in turn, their controls and meters are displayed alone in the GUI. Three of Ozone's six modules offer multiband processing. You can split the dynamics, harmonic exciter, and stereo-imaging modules into as many as four frequency bands and adjust the bands' crossover points. This allows you to, for example, compress only the bass frequencies, add harmonics to just the midrange, and widen the stereo image solely for the highs.

Four of Ozone's six modules (all but the stereo imager and maximizer) can be set — independently of one another — to process either the stereo or mid and side (M-S) channels of your mix. The mid channel comprises everything that is panned to the center of your mix (typically, kick drum, snare, bass, and lead vocals). The side channel contains all elements of the mix that are dissimilar in the left and right channels, such as hard-panned instruments and reverb returns.

You can use M-S processing to compress only center-panned tracks (the mid channel), for instance, without affecting the dynamics of hard-panned tracks. Or add Ozone's mastering reverb to the side channel to soak hard-panned guitars in a wash of ambience while leaving tracks in the center untouched. You can toggle Ozone's I/O meters to read either stereo or M-S levels.

Master controls allow you to increase or decrease the overall amount of processing independently for each module and for the entire plug-in. You can also bypass individual modules and change their order in the signal chain. More than 370 parameters in Ozone can be automated (assuming your digital audio sequencer supports effects automation).

Drilling Deeper

Ozone's Paragraphic Equalizer module lets you mix and match eight bands of bell-curve, highpass, lowpass, and high- and low-shelving filters (see Fig. 1). Choose either linear digital filters or analog-modeled ones that emulate vintage tube gear. Adjust the frequency, gain, and Q (bandwidth) of each band to taste. You can also capture the frequency spectrum of a favorite mix and make your current mix mirror that response.

Ozone's Mastering Reverb module offers both plate and room reverbs. You can control the reverb's size (tail decay), pre-delay, width, high-frequency damping, bandwidth, and wet/dry mix.

FIG. 2: In Ozone''s Multiband Dynamics module, vertical lines in the upper graph can be dragged sideways to adjust the crossovers. Here the I/O meters show stereo levels.

FIG. 2: In Ozone''s Multiband Dynamics module, vertical lines in the upper graph can be dragged sideways to adjust the crossovers. Here the I/O meters show stereo levels.

The Multiband Harmonic Exciter module can be set to emulate transistor, tape, or tube saturation. A new, fourth saturation mode generates only quickly decaying even harmonics. You can separately adjust the amount of harmonics and the wet/dry mix for each band. You can also delay each band by separate amounts to compensate for group delay; for example, delaying the low-frequency band slightly can make a flabby kick drum sound tighter.

A separate compressor, limiter, and expander in each band of the Multiband Dynamics module have their own threshold, ratio, attack, and release controls (see Fig. 2). The expander can produce either upward or downward expansion. You can defeat the module's automatic makeup gain and choose either RMS or peak detection for the common sidechain. You can also adjust the balance of processed and unprocessed sound in each band to create parallel compression effects, thereby preserving transients.

Ozone's Multiband Stereo Imaging module can make your mix's stereo width either wider or narrower in each of up to four frequency bands. For example, I could collapse the bass frequencies to mono to add focus to a mix's bottom end and simultaneously widen the highs for a bigger soundstage.

The Loudness Maximizer module gives you a choice of four different types of digital and analog-modeled limiters. Adjust the threshold, margin, and release controls to reduce peaks and increase the average loudness of your mix (see Web Clip 1). Ozone provides an assortment of dithering and noise-shaping options, too.

Reading the Meter

No mastering program would be complete without a full arsenal of meters and analysis tools. Ozone 4 offers far more than just traditional I/O and gain-reduction metering.

The plug-in's I/O meters can be switched to show either stereo or mid-side levels. You can adjust or completely defeat the peak-hold time. The meters can be made to detect intersample peaks that might otherwise go unnoticed on traditional, digital peak meters and therefore cause distortion.

Choose RMS or peak ballistics, or have the meters show both levels at once. Alternatively, you can choose K-System metering with simultaneous peak and RMS displays. K-System metering offers three different scales and associated headroom references that are tied to standardized monitoring levels (that is, for use with monitors producing a known, fixed SPL at the mix position). Its purpose is to provide consistent perceived loudness and preserve dynamic range in music produced for different applications (such as CD release, film, or broadcast).

Ozone's dithering section allows you to filter out headroom-robbing DC offset and see on a dedicated meter how many decibels of DC signal have been removed. A separate bit meter alerts you when unwanted word-length truncation occurs upstream of Ozone and confirms you are dithering properly for your destination format. (See the online bonus material for more about Ozone's metering and spectrum-analysis tools.)

Kudos and Dings

Ozone's paragraphic EQ sounds excellent. However, the type of filter chosen for each band and its active or bypassed state must be the same for both mid and side channels. This limitation makes it impossible to prevent an activated highpass or lowpass filter in one channel from altering the response of the other. (Other filter types can have their gain settings nulled as a workaround.)

In addition, Ozone 4.03 doesn't provide master level controls for mid and side signals. Instead, you must rebalance the mid and side channels (if desired) by using processing in one of the M-S-capable modules to effect gain changes. I found the most transparent way of doing this was to null all the controls in the Multiband Dynamics module and then adjust the separate global gain controls for that module's mid and side channels.

The mastering reverbs, stereo imaging, and harmonic exciter all sound great. The latter, when used frugally, can add wonderful size and luster to a flat, dimensionless mix.

In addition to mastering, you can also use Ozone to process individual tracks or subgroups on buses. The plug-in is a CPU hog, however, and drained 55 percent of my 8-core Mac Pro's CPU resources with all of Ozone's modules and displays in use. I could reduce that drain to just under 25 percent by using only three modules at once, limiting multiband processors to just one band, and disabling all dynamic displays except the I/O meters. Anyone who uses all six modules at once is probably going overboard and ruining his mixes, anyway.

Ozone's learning curve is steep, but anyone who ventures beyond the presets will be rewarded with sophisticated mastering capabilities. Thankfully, the HTML-based owner's manual (the only available documentation) is very thorough. Ozone 4 offers high-quality sound and a boatload of features at a bargain-basement price.

EM contributing editor Michael Cooper is the owner of Michael Cooper Recording in Sisters, Ore. Hear some of Cooper's mastering work at

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