Review: iZotope RX 6, Cutting Edge Audio Repair Tools

iZotope's RX is one of the most powerful audio repair tools in the business. So what could a new version add? Quite a lot, as Joe Albano found out...  

iZotope’s RX has established itself as the premiere audio repair software - its collection of cutting-edge tools and spectral processing capabilities has been used to clean up and improve countless bits of problem audio over the years. The latest version, RX6, adds a number of significant new features and processors to the party so let’s take a look at what’s on hand in this update..

The RX6 Family

iZotope RX 6 family

First off, RX6 is now available in four versions.. The top-of-the-line is RX6 Advanced, which contains all the processing modules available for RX, including the new ones, for the most full-featured set of tools. RX6 Standard offers a slightly smaller subset of the full toolbox for a reduced price, but it does contain most of the key modules, including the ones RX is best known for like Spectral Repair. For those on an even more modest budget, RX6 Elements is a smaller collection of basic repair tools, perfect for quickly cleaning up the most common flaws in typical recordings. A full comparison chart is available on the iZotope website. In addition to these options, for post production pros, RX6 Advanced is also available as part of the RX Post Production Suite 2, which also includes Neutron Advanced, Loudness Control and Insight.

General Features

iZotope RX 6 Advanced GUI

RX6 (I’ll be describing RX6 Advanced here), just like previous versions of RX, consists of a standalone application with a collection of processing “modules”, each of which offers a targeted solution to a specific audio issue. Many of these are also available as plug-ins in all the standard formats (AAX, AU, VST), for use in realtime within your DAW of choice. When processing needs to be in the standalone (some of the more advanced types of audio tweakery, including the graphic  techniques of Spectral Repair), RX6 provides a way to quickly transfer audio back and forth between the DAW and RX6 standalone - this varies in different DAWs, from using the RX Connect plug-in to assigning RX6 as the designated external audio editor.

iZotope RX 6 in Pro Tools

Within the standalone, there are numerous features for enhancing workflow. Module Chains (savable as presets, as are all module settings) let the user assemble and quickly apply a string of modules, speeding up tasks that involve multiple processing. RX6 offers additional workflow improvements: an improved Find All Similar helps to quickly locate similar problems in a longer audio file, and there are new options for displaying the extensive module list by user category. 

RX6 also introduces Composite View, a quick way to simultaneously process multiple files. While RX has always had batch processing capabilities via a dedicated window, Composite View is a more efficient way to temporarily group all open files together and apply processing to them all at once. While there are a few common sense restrictions, it could speed up workflow for many tasks that need to be performed across multiple bits of audio.

New Modules

Naturally, RX6 includes all the modules from previous versions, including (among others) De-click, De-clip, De-hum, De-plosive, De-reverb, Spectral and Voice De-noise, Deconstruct, and of course Spectral Repair as well as its collection of utility modules like Leveler, Loudness, Time & Pitch, Resample, EQ Match and many additional general-purpose modules. Some of these have incremental improvements - De-click, De-plosive, Voice De-noise, Ambience Match, Deconstruct and Center Extract all benefit from tweaks to their engines (I particularly noticed the difference in De-click).

To this already comprehensive collection of audio tools RX6 has added several new Modules: De-ess and Breath Control are broken out of the Leveler modules into separate modules with more comprehensive controls; Mouth De-click does the regular De-click one better, being targeted specifically to lipsmacks and other mouth-related clicks and noises; De-rustle and De-wind provide solutions for particular post production issues; Dialog Isolate pulls a voice up and/or out of a busy background; and De-bleed addresses that all-too-familiar problem of leakage, like from headphones worn during a recording. Each of these offers something specifically targeted to a particular problem so let’s take a quick look at them.

De-ess & Breath Control

De-ess & Breath Control

In previous versions of RX, the Leveler module included simple ess-reduction and breath control options - basically just on-off and a sensitivity slider - but these new dedicated modules offer a lot more user control. De-ess provides settings for fine-tuning the frequency and speed of the de-essing, and it also offers a new Spectral De-essing mode, which applies spectral analysis and processing to the task of isolating and eliminating harsh sibilance. This can potentially make for more effective de-essing, with controls that allow the user to shape and tilt the spectral character of the sibilance, for more natural results. The new Breath Control module adds options for both amount of breath reduction and sensitivity to breath sounds, which seemed to me to isolate breaths even more precisely than the older version. 

Mouth De-click

Mouth De-click

I’d never been able to get the regular De-click module in previous RX versions to reliably eliminate that problem on my own voice, but not only does the improved De-click do a better job, the dedicated Mouth De-click module works like a charm! Even at its default settings, this module seems to nail every bit of audio I’ve thrown at it, and it also provides additional controls to fine tune the detection and processing - whatever iZotope has done to tweak the general de-clicking algorithm to address dedicated mouth sounds, it seems to make a significant difference.

De-rustle & De-wind

De-rustle & De-wind

These two are primarily for post production use, though of course they could come in handy on any application that suffers from those issues. De-rustle is aimed at removing or reducing the rustling sound of clothing rubbing up a lavalier mic. Like a number of the new modules, this addresses background noise that’s more irregular, and wouldn’t be handled as well by the standard De-noise modules, which do better learning & processing more steady, regular unwanted background sound. With a couple of files I threw at it, De-rustle was able to deal successfully with even fairly intrusive noise. A nice feature is an Ambience Preservation control, which allows De-rustle to remove rustling sounds while leaving other (possibly desirable) ambient sound intact.

De-wind addresses the problem of wind noise in outdoor recordings - the irregular and intrusive rumbling from wind shaking a mic’s diaphragm. With a couple of torture-test files I threw at it that suffered from especially loud wind noise, De-wind acquitted itself admirably - it should have no trouble with more typical subtle wind problems. A Fundamental Recovery control helps to restore any fullness in a voice lost to more aggressive processing, and Artifact Smoothing (a control common to many modules) helps to mitigate any hint of the watery-sounding artifact that sometimes accompanies this kind of FFT-based audio processing.

Dialog Isolate

Dialog Isolate

This ambitious module lets you isolate a voice from background sound in a recording, or even vice-versa - pull a voice out of a recording, leaving just background sound (or music). Once again, unlike the existing Voice De-noise Module, Dialog isolate is tuned to be more effective with irregular background sound, rather than the regular noise the De-noise modules are designed to address. 

And it works surprisingly well. I was able to substantially reduce the level of some especially intrusive background noise (subway train going by, loud voices is an ambient room), drawing out the primary voice until the background was, if not completely gone, largely unnoticeable; with less egregious examples of background sound, Dialog Isolate should be able to fully eliminate the undesirable noise. I wouldn’t necessarily expect it to be able to, say, completely lift a vocal out of a busy mix, especially one that’s somewhat buried in the mix, but considering how well it did isolating two voices (interviewer and subject) from background voices that were practically as loud as the main voices, it’s well worth trying on any recording - as with many of these processes, sometime multiple passes can provide an extra degree of effectiveness.



Finally, the new De-bleed module addresses the familiar issue of leakage, or bleed. As everyone knows, this can come from headphones during a recording (especially if a singer removes one earcup unnoticed, as they’re often inclined to do), in the form of the rough mix that was playing through the cans, or as the dreaded sound of a click track. Acoustic leakage, from other instruments in a live session, can also compromise the integrity of a track. But De-bleed can come to the rescue, if you’re careful to set it up properly..

De-bleed requires two files to do its thing: an “Active” track - the recording with the unwanted bleed - and a “Bleed Source” track - the track that contains the original audio that leaked into the Active track. For example, in a scenario with, say, an acoustic guitar recording that was cut to a click track in headphones, the guitar, naturally would be the Active track, and the original click track the Bleed Source. With a recording of a singer with bleed from a rough mix, the mix itself would be the Bleed Source. Both files must be loaded into RX6 (currently, De-bleed only works in the standalone version), and to be most effective, they need to be time-aligned. When I tested this, I bounced down the appropriate section of a leaked mix and lined it up with the vocal (which was an overdub) in the DAW, and then brought both files into the RX6 Advanced application. 

And it worked! De-bleed Learned the profile of both tracks, and even though the bleed in my test file was quite loud (the singer had removed one earcup), and my Bleed Source mix file was not really the exact same rough mix as the one that had leaked into the vocal recording (I’d reconstructed it after-the-fact), De-bleed almost completely eliminated the leakage, especially under the vocal, where it really counted.


So that’s what’s new and exciting in RX6 - while some of the new modules might seem at first glance to be merely refinements of existing features, in practice most offer significantly improved performance, along with much greater flexibility. And Dialog Isolate and De-bleed really do take audio repair to the next level. RX6 should be part of any audio engineer’s collection of tools, and with the various versions available, there’s no excuse not to have at least some of its features available for cleaning up your tracks and making them shine! 

Price: RX6 Advanced: $1199 (regular); $799 (sale price)

RX6 Standard: $399 (regular); $299 (sale price)

RX6 Elements: $129 (regular); $99 (sale price)

RX Post Production Suite 2 (incl RX6 Adv): $1499 (regular); $999 (sale price)

Pros: Powerful collection of cutting edge tools for audio repair

Cons: Smaller/budget versions may omit that one feature you really wanted




Joe is a musician, engineer, and producer in NYC. Over the years, as a small studio operator and freelance engineer, he's made recordings of all types from music & album production to v/o & post. He's also taught all aspects of recording and music technology at several NY audio schools, and has been writing articles for Recording magaz... Read More


Izotope RX6 is awesome! But beware of purchase policy! If you order the wrong thing from among all of the versions, special prices, and upgrades you are completely out of luck. Ask for a refund on the incorrect purchase and all you get is a "get lost order the right thing!" I did after digging through all the webpages and I am out $299. I had a direct upgrade path from RX5 to RX6 Advanced that it took 40 minutes to find after thinking I would get what I needed in RX6 Standard. At $499 Advanced is a bargain, but not when you get screwed on a mistake!

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