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iZotope RX6

Restoration Software [Mac OS X/Windows] By Hugh Robjohns
Published August 2017

All three versions of RX6, including the most affordable Elements edition, now include the stand-alone editing application.All three versions of RX6, including the most affordable Elements edition, now include the stand-alone editing application.

Whether you’re a professional working in post-production or a humble home studio user, there’s a version of iZotope’s RX restoration software to suit you.

My diary reminds me to celebrate a startlingly large number of annual events. For example, springtime in Britain brings us April Fool’s Day, the charity fund-raising Red Nose Day, Earth Day, as well as Mother’s Day, the Queen’s Official Birthday, and a smattering of bank holidays, to list just a few. My American friends even have a National Beer Day, which sounds like a lot of fun. However, the one reliably regular event that doesn’t appear in my diary — but really should — is RX Day! I’m not quite sure which day it should be, exactly, but it has become unswervingly dependable that a new version of iZotope’s superb audio-repair tool will appear around April each year.

As the version number increments annually, we are now up to RX6, and this latest release sees the introduction of no fewer than 10 completely new features and processing modules, plus valuable updates to seven of the existing modules carried over from RX5. Most of the new processing modules are the result of ‘machine learning’, a technology whereby a computer algorithm examines a large number of tracks with a specific type of audio problem, and essentially teaches itself to recognise and remove the unwanted noises. In other words, iZotope are using artificial intelligence to fix our broken recordings. If only we had the natural intelligence not to make broken recordings in the first place, eh!

Elementary, My Dear Watson

There are now three different variants of RX, starting with the relatively affordable entry-level RX6 Elements (which, in effect, replaces the previous RX Plug-in Pack), continuing with the most popular RX6 Standard edition, and culminating in the full-fat, all-options-included RX6 Advanced package, which is, it can’t be denied, pretty pricey! For demanding TV and film post-production users with generous budgets, the full RX6 Advanced edition is also available as part of a bundle in iZotope’s RX6 Post-Production Suite 2, which also includes the company’s Neutron Advanced, RX Loudness Control and Insight metering products, providing all the software tools anyone could possibly need to optimise their media sound.

As you would expect, the low-cost RX6 Elements variant has limited functionality compared to the other editions, but it still contains a broad core of very useful and powerful tools. In essence, it is the former Plug-in Pack, but with the stand-alone Editor application bundled as well, so all the standard audio recording and editing facilities of the Standard and Advanced editions are provided, with tools to normalise or fade a track in or out, and to adjust its gain, phase rotation, stereo width and balance. Also included are a signal generator, spectrum analyser, waveform and spectrogram displays, waveform statistics reporting tool, a batch processor, and the ability to host third-party plug-ins in VST or AU formats within the RX environment.

Among the key processing modules/plug-ins included in RX6 Elements are the superb Spectral Editor, which now has an improved Find Similar function to speed up the correction of repeating noises, the Voice De-Noise module, which works on both dialogue and sung vocals and is a variant of the Dialogue tab in the original De-Noise module, and the De-Clip, De-Hum and De-Click modules, the last of which is newly and very clearly improved. This suite of sophisticated audio-repair tools represents the core functionality of the original RX suite released back in 2008 — except that they’ve all improved considerably over the intervening years, both in capability and usability. There’s certainly enough functionality in RX Elements to deal with most routine audio-repair situations, and it’s all provided at a pretty attractive price, too. In fact, at roughly half the price of the original RX release, it’s a genuine bargain!

Raising Standards

Excellent though the tools in RX6 Elements are, sometimes more challenging unwanted noises crop up, and that’s where the extended capabilities of the RX6 Standard edition become more appropriate. This variant retains everything provided in RX6 Elements while adding a further 21 features, six of which are brand new to RX6. With such an extended feature set, it’s not surprising that the RX6 Standard suite costs nearly three times as much as the RX6 Elements edition.

For RX5 users, the carried-over modules will be quite familiar, and include De-Crackle, along with an improved version of the excellent De-Plosive module; as this was previously only available in RX5 Advanced, it is a most welcome addition to the RX6 Standard edition. There are also De-Reverb and Dither modules, the latter offering iZotope’s MBIT+ noise-shaping algorithms, a six-band parametric EQ, the alternative Interpolate method of repairing clicks and dropouts, Pitch Contour for removing pitch drifts and cyclic variations, sample rate conversion, and the original de-noising module, which has now been reinvented as Spectral De-Noise, with the dialogue tab removed and reformed into the new Voice De-Noise module, plus Spectral Repair and Time and Pitch correction.

The Standard edition also includes the RX Monitor and RX Connect functions, which allow the RX6 processes to be neatly integrated within your preferred DAW, greatly improving workflow on repair-intensive projects. Also included is the Instant Process mode, another potential time-saver that permits audio faults to be ‘painted out’ directly in the edit screen without having to launch and run specific process modules.

RX6 Standard features four new modules aimed at vocal processing: De-Ess, De-Bleed, Breath Control and Mouth De-Click. RX6 Standard features four new modules aimed at vocal processing: De-Ess, De-Bleed, Breath Control and Mouth De-Click.

In The News

Of the six brand-new processing modules in the RX6 Standard edition, the first four are aimed at vocal processing tasks, and two are enhanced forms of processes that were, and still are, embedded within the Leveller module. They include a dedicated Breath Control module to automatically suppress breath sounds in dialogue and vocal tracks, a De-Ess module that can operate in classic broadband mode or a spectral frequency-specific mode, and Mouth De-Click to remove lip-smacks. The fourth, a De-Bleed module, reduces the leakage of one signal onto another, such as headphone spill onto a vocal take.

A fifth new option is an MP3 export facility included as part of the file export dialogue. This offers constant, average or variable bit-rate modes, and sits alongside the existing WAV/BWF, AIFF, OGG and FLAC options. It would be nice if Apple’s ALAC format was added one day, too...

Also new in RX6 Standard and Advanced is the ability to export audio in MP3 format.Also new in RX6 Standard and Advanced is the ability to export audio in MP3 format.The final brand-new module in this edition of the software is called Composite View, and in essence, this processes up to 16 separate audio tracks as a single composite process (each having first been set up as an active tab in the RX window). RX has long had a batch processing mode which could be used in a similar way, but the new Composite View mode is a nicer and quicker way of working. In short, it allows multiple files to be processed simultaneously with any selection of modules, which makes it much easier to carry out identical repairs across multiple related source tracks, such as when you need to edit a chair squeak out of a number of separate mic channels on an orchestral multitrack recording.

Bold Advances

As usual, the flagship version is the RX6 Advanced edition. The (substantial) extra outlay brings even more significant extra features above and beyond everything included in the Standard suite, and most of them are geared primarily towards TV and film post-production applications. In brief, the Advanced edition provides 10 further processing modules, of which three are wholly new to RX6 Advanced and three more are improved versions of those provided in the previous RX5 generation.

The brand-new processing options start with a Dialogue Isolate module, designed to improve the audibility of dialogue above ambient background sounds such as traffic, weather, crowd noise and so on. In the 1970s, Dolby found that their A-type noise reduction system could be used as a multiband downward expander to help clean up location dialogue tracks, and repackaged the system as the Cat43. iZotope’s Dialogue Isolate module builds on that concept and is extremely effective. Similarly, the new De-Wind and De-Rustle modules also do exactly what their names suggest, removing the typical wind noise and clothing rustles commonly associated with location sound acquisition. They are both more effective and easier to optimise for these roles than general-purpose noise-reduction modules.

Among the improved modules, Ambience Match helps to create a smooth ambient noise floor behind constructed dialogue tracks and now gives smoother level matching (which is particularly important when generating an ambience-only ‘atmos’ track), while Centre Extract removes the central sound elements in a stereo track, and now does so with fewer processing artifacts and a dry-mix control in case you want to retain some of the original full mix at a low level. The Deconstruct module, which allows the noise and tonal elements of a sound to be adjusted independently, sometimes offering a useful alternative approach to noise-reduction tasks, has also been improved, with a new transient gain control and reduced processing artifacts.

Other processing modules exclusive to the RX6 Advanced edition include EQ Match, which can apply the tonality of one signal to another, the Leveler for automatically controlling the dynamics of dialogue tracks, the Loudness module that adjusts a track’s perceived loudness to conform with BS.1770 requirements, and Azimuth, which applies automatic correction for inter-channel delays or level errors, such as can happen with a misaligned tape head or mis-tracking stereo faders.

Perfect Sixth?

I was provided with the Advanced version of RX6 for this review, and on firing it up, I was pleased to see the stand-alone editor window is very similar to the previous RX5 version. However, although there’s no new learning curve to climb, there are a couple of small, but useful, differences to the main control panel.

The first obvious addition is a new button alongside the Instant Process tools below the waveform display. This provides direct access the Clip Gain feature, similar to the node-based fader/envelope automation facility in most DAWs, which was previously hidden under the View drop-down menu tab. Secondly, the right-hand modules list has evolved slightly as some of the icons have been revised, some of the old familiar modules have gone, and lots of the functions that were previously accessed through the top-line drop-down menus or from within other (now abandoned) modules have all acquired their own independent module status.

As a direct result, the modules list is a lot longer than in RX5, and to help reintroduce some order, the processing modules are now grouped into three separate categories called Repair, Utility and Measurement, each of which can be expanded or hidden. The Measurements category provides direct access to tools like the Spectrum Display, Markers and Waveform Stats that were all hidden under the top-line drop-down tabs in RX5, while the Utilities category incorporates many of the tools that were previously bundled within other modules, such as the former Channel Ops module, which has now been discarded.

To help manage this now-lengthy module list, iZotope have also introduced another new feature called Module List Filters. This allows the user to create customised subsets of modules that can be saved and recalled as personal presets, complete with assignable quick-access keyboard shortcuts. The outcome is an elegant way of grouping together just the tools required for specific regular tasks, reducing screen clutter and generally improving the workflow.

Magic Modules

As for the new and revised processing modules, it’s impossible not to be impressed — if not utterly gobsmacked! — at the capability and sophistication on offer here. The basic functionality of the new vocal-processing tools (Breath Control, Mouth De-Click, De-Ess and De-Bleed) could all be achieved using the tools in RX5, given some time and a lot of skill, but these new modules make such tasks a lot quicker and much easier by being expertly targeted and tailored.

The De-Bleed tool is particularly useful and effective, although it does require fairly accurate time-alignment between the master track suffering the unwanted bleed and the unwanted spilling sources. For reference, it also needs a clean copy of the track that is the source of the spill. Consequently, in situations where headphone spill is likely to be a problem, it would be well worthwhile recording the headphone cue feed to a spare track on the DAW during the session, especially if it’s a click that might not otherwise exist anywhere as a reference track.

The full Advanced version of RX6 includes the four vocal processing modules new in the Standard version, and adds De-Wind, Dialogue Isolate and De-Rustle. The full Advanced version of RX6 includes the four vocal processing modules new in the Standard version, and adds De-Wind, Dialogue Isolate and De-Rustle.

In the Advanced suite, the new Dialogue Isolate, De-Wind and De-Rustle modules will be a real boon to dialogue editors. Again, although these issues could be tackled reasonably well with the previous suite of tools, these new modules are so much better targeted for dealing specifically and quickly with these all-too-common problems.

Overall, RX6 builds constructively on the previous generation, with some small but useful enhancements to the user-interface and a generous number of significantly improved and intelligently focused new modules making it easier and quicker to tackle a variety of specific problem noises. The leading highlights of RX6 are undoubtedly the De-Bleed module for music applications, and the Dialogue Isolate module in sound-for-picture applications — and these really do work well.

One frustratingly obvious omission from RX6 (still) is its inability to handle and process multi-channel source files natively. This continues to surprise me, given how long standardised surround-sound formats have been with us, and especially considering the rapidly growing interest in virtual reality and its associated source sound formats. The ability to process multi-channel sound files is going to become increasingly important for a large sector of the potential market, and although RX6’s Composite View can be of help in this respect, it’s really not the ideal solution.

Getting the very best from RX does take time and dedication — the module controls are not always entirely obvious or intuitive — but it gets easier with each new iteration, and iZotope’s online manuals are very helpful. While the Standard and, especially, the Advanced editions may seem expensive, there really is nothing else that gets anywhere close for the price. More importantly, perhaps, for anyone unsure about dipping their toes in the RX waters, the new RX6 Elements edition is an extremely capable and attractively priced introduction, and I thoroughly recommend RX to anyone who regularly needs to repair audio files to high standards.


The gold standard in audio restoration is CEDAR Audio’s Cambridge Suite, which is similarly comprehensive, but even more technologically advanced and often rather easier to use. However, it costs significantly more.

Fix It In The RX?

iZotope’s processing tools are incredibly powerful, and in skilful hands, they can deliver quite astonishing results. However, I am very wary of the dangers of believing everything is fixable in the box, and so I believe it important to keep a realistic outlook. It is not always possible to provide perfect and flawless ‘cures’ for badly recorded audio, and if that’s the end-user’s expectation, they may be sadly disappointed. We must always strive to make the best possible source recording, and spending a little extra time and effort optimising that saves countless hours and frustration in post-production later. In other words, it is always better to spend the time getting a source recording right, rather than knowingly record something sub-par in the hope that it can be ‘fixed’ later — even if you do have all the wonders of RX6 Advanced waiting on the computer!

Having said that, I have been using RX in all its incarnations for a decade or more now, and know very well how dramatically it can improve unwanted, annoying or distracting noises — often to the point where few would notice their presence at all. However, trying to achieve total perfection is a fool’s game, and pushing things too far often results in unpleasant processing artifacts that are frequently more obvious and annoying than the original unwanted noises! I find that the route to really superb results is to employ several gentle processing passes rather than a single heavy-handed effort, or to use a conservative combination of different tools, each tackling the problem noise in a slightly different way — and RX6 certainly offers a great deal of flexibility in its range of processing modules.

Open DAW Policy

For many, DAW integration is an important facet of working with RX, and this is where the RX6 Standard and RX6 Advanced editions have an advantage, because they can be used in three distinctly different ways. Often, the most appropriate configuration is as a completely independent audio editor/processing platform in its own right, and this is the de facto mode that the RX6 Elements edition supports. However, the Standard and Advanced editions can also be used as an external editing/processing tool tied directly into a DAW via the RX Connect module.

It is also possible to use the core modules as a suite of independent plug-ins directly within a DAW, although not all of the RX6’s many processing modules can be used as independent DAW plug-ins. Nevertheless, the plug-in list is quite extensive and includes Ambience Match, Spectral De-Noise, Voice De-Noise, De-Reverb, De-Plosive, De-Hum, De-Ess, De-Clip, De-Crackle, De-Click and Mouth De-Click. All the usual plug-in formats are supported, including AAX, AU, RTAS, VST and AudioSuite, while RX6 can be run on Windows 7, 8 and 10, or Mac OS 10.8.5 to 10.12.


  • Several powerful new processing modules, including De-Bleed and Dialogue Isolate.
  • Many processing modules have been upgraded to give better performance and easier control.
  • Easier access to utility processes and measurement tools.
  • Elegant new module grouping and display functions.
  • Ability to process multiple files simultaneously within the RX editor window.
  • Extremely cost-effective RX Elements edition, which includes the Editor application along with a broad range of essential processing modules.


  • The Advanced edition and, to a certain extent, the Standard edition may appear expensive — but really aren’t!
  • Still no native ability to handle multi-channel (surround) sound formats.


The RX platform continues to expand and improve, both in its usability and its processing capabilities. RX6 implements several workflow enhancements, as well as a number of new processing modules that target specific audio problems very effectively indeed.


RX Post Production Suite 2 £1175; RX6 Advanced £939; RX6 Standard £315; RX6 Elements £99.95. Prices include VAT.

Time + Space +44 (0)1837 55200

RX Post Production Suite 2 $1499; RX6 Advanced $1199; RX6 Standard $399; RX6 Elements $129.