iZotope RX 3 Advanced review – More Than Restore

Now in its third revision, iZotope’s premier audio restoration tool gains new modules and even more spectral prowess. Mark Cousins applies some forensic analysis in our review of RX 3 Advanced   Manufacturer iZotope Price £909 (RX 3 Advanced), £259 (RX 3) Contact Time + Space 01837 55200 Web:    RX 3 – Time + […]

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Now in its third revision, iZotope’s premier audio restoration tool gains new modules and even more spectral prowess. Mark Cousins applies some forensic analysis in our review of RX 3 Advanced

Manufacturer iZotope
Price £909 (RX 3 Advanced), £259 (RX 3)
Contact Time + Space 01837 55200
Web:    RX 3 – Time + Space    RX 3 Advanced – Time + Space

Key Features
7 Repair Modules
8 Utility Modules
Plug-in and standalone operation
iZotope 64-bit SRC™
MBIT+™ dithering
iZotope Radius® for changing time and pitch

Even in a world of pristine digital recording, it’s not uncommon to find audio quality harmed in some way: whether it’s high levels of noise, mains hum, clicks, crackles or a range of other audio gremlins. The task of audio restoration, therefore, is something few of us can completely avoid, while for others – notably those working in forensic audio, or a mastering engineers re-mastering vintage recordings – the ability to coax audio back into a more listenable form is a day-to-day necessity.

Alongside solutions from Cedar and Sonnox, iZotope’s RX has received plenty of praise over the years for its audio restoration abilities. RX’s strength is in the diversity of tools it offers, making it suitable not just for vinyl restoration (using the familiar click and crackle removal algorithms) but also a range of audio restoration activities, including de-clipping and spectral repair. In short, RX is a veritable swiss-army knife of audio restoration, which is why the latest version – RX 3 – has garnered plenty of interesting in post production circles.

Third Generation
RX 3 works as both a standalone application and as a series of plug-ins covering many of its principle repair functions. While the plug-ins are a welcome addition for those not wanting to leave the comfort of their DAW, there’s little doubt that RX 3 really shines when you’re using it as an application. The RX 3 environment is designed specifically for the task of audio restoration, with a prominent Spectrogram/Waveform display alongside various modules found along the right-hand side of the interface.

One of the key qualities of RX 3 is its ability to select audio in both time and frequency-based domains, which explains why the spectral display is so important to RX 3’s operation. Rather than just highlighting the audio over a given time-frame, therefore, you can use a variety of selection tools to grab just a part of the frequency spectrum across the whole audio file, for example, or ‘magic wand’ a specific harmonic, or number of harmonics, within a given sound. While this approach isn’t completely unique, it’s clear that RX 3 has been built from ground-up with this functionality in mind, making audio editing akin to picture editing in Photoshop.

Reverb Killer
Some of the biggest interest in RX 3 stems from its new modules – most notably the Dereverb and the all-new Dialogue Denoiser. The Dereverb module can perform the seemingly impossible task of reverb removal, offering the ability to attenuate or enhance the reverberant components of a signal. As with all audio restoration tasks, it works best when the Dereverb modules is given a slice of audio so that it can ‘Learn’ characteristics from (in the this case, a portion of audio with discernable direct and reverberant elements), but even with a relatively reverb-heavy sound file, the module performed an admirable job, even if it was just to tame the reverb.

Although RX 3 comes with a highly effective Denoise module, it’s also interesting to note the addition of a new Dialogue Denoiser. The Dialogue Denoiser uses a similar form of noise reduction technology to the Denoiser modules, but is optimized specifically for the task of dialogue removal. One of the principle differences between the two modules is the amount of frequency bands used – 64 bands instead of the thousands used for FFT-based noise reduction – which arguably results in a reduction of bell-like artefacts, and also means that the module can run with zero latency. As the band positioning is optimized for dialogue, the results are quick and effective, making the Dialogue Denoiser a great tool for dialogue mixing in post production.

Of course, for more challenging noise problems across a wide range of audio sources, the Denoiser is probably the better choice of module to use. Ultimately, though, it’s great to see iZotope understanding the diverse requirements of noise reduction, and how one tool might not be ideal for every application.

Audio Hygiene
Beyond these key new features, though, there’s plenty of depth to RX 3, some of which is present from earlier version, but also a host of new additional workflow improvements. One interesting development is the new file format – an RX document – that you can use to save your work. The key advantage of the RX document format is that the undo states remain in place, and remain ‘undoable’ even after the file has been subsequently closed and reopened! Given the destructive nature of off-line audio restoration, this is a welcome new addition.

For new users, there’s plenty of powerful features in RX 3 present from the older version of the application that are worth identifying. Modules like the Deconstruct option (which separates the signal into tonal and noisy component) as well as the Declip function really indicates the spectral prowess of RX 3, often performing audio feats that many would have thought previously impossible. The Batch processing also means that repetitive tasks can also be kept to minimum, which is an essential option for sounds designers needed to work with hundreds of sound files for a given project.

Ultimately, the deeper you explore the RX 3 universe, the more you begin to realise what it can achieve. For example, using RX 3’s ability to select elements on a spectral level, combined with support to third-party VST and Audio Unit plug-ins, really takes the application onto a whole new level. In our experiments, we got some great results feeding spectral parts of a vocal through various modules in Native Instruments’ Guitar Rig. Indeed, you soon realize that there’s far RX 3 than just audio restoration activities!

Although there’s a clear bias towards RX 3 as a standalone application, it’s also good to see eight plug-ins also included with the package: covering the Declicker, Declipper, Decrackler, Denoiser, Hum Removal, Spectral Repair, Dereverb and Dialogue Denoiser modules. For music applications – where offline file rendering is much less important, and real-time plug-in operation is essential – the ability to use RX 3 repair tools in plug-in form is welcome.

Clean Slate
Although it’s easy to dismiss RX 3 as just another ‘audio restoration tool’, it’s clear that iZotope’s intentions are far broader than this might suggest. For those of a creative persuasion, RX 3 spectral approach is an eye-opening window on a new way of working with sound, making it a unique and interesting tool for sound design. Whether you’re using the Deconstruct module, for example, or literally painting with spectral sound, there’s an opportunity for sound designers working in the games or film industry to get plenty of millage from RX 3.

Looked at purely from an audio restoration angle, RX 3 has a fair degree of competition – like Cedar, at the very top-end of the market, but also plug-ins from the likes of Sonnox and Waves. In keeping with many of these products, RX 3 is a premium product with a price tag to match, but as with the older version of the application, iZotope have thoughtfully offered RX 3 in two flavours – the fully-fledged RX 3 Advanced; which includes all the modules and options we’ve described, and a slimed-down RX 3; which omits the Dereverb and Dialogue Denoiser modules and some of the other less essential features.

Along with Ozone and Insight, iZotope have produced a range of impressive, professional products that demonstrate a meticulous attention to detail with respect to audio quality. RX 3 is a shinning example of this methodology in action, providing forensic-level analysis and deconstruction of your audio that no other plug-in solution can match. Moving on from RX 2, it’s also pleasing to see the application receiving a timely facelift and various ‘under the bonnet’ performance tweaks, all of which make RX 3 an efficient and productive audio tool.


+ Powerful spectrum-based sound editing
+ Great new Dialogue Denoiser
+ Dereverb is surprisingly effective
+ More than just an audio restoration tool
– Full version is expensive
– Steep learning curve

iZotope’s RX 3 is one of the finest audio restoration systems available, but its scope and creative potential is far greater than you might first imagine.


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