iZotope RX2 vs RX3 – What’s Changed?


2014 01 RX Changes Hero 2

I recently purchased iZotope’s RX3 software. RX is the well-known industry standard for repairing damaged audio.

RX3 was released last fall as a paid upgrade to its popular predecessor. It refined some tools, and introduced some new ones, notably the Dereverb and realtime Dialogue Denoise modules.

The upgrade has received a lot of press lately. But is it hype, or a helpful upgrade?

Today I’ll focus on one thing: the feature differences between RX3 and RX2. I’ll get to audio quality and examples at a later date. And, since I record and master field recordings, this post will have a strong sound effects mastering slant.

New to RX? No problem. I’ll also include an overview for those of you unfamiliar with the software.

Ready for a deep dive into the new RX3 features? Grab a coffee (this is a long one) and read on.


Overview of the RX Software

What is RX?

iZotope RX was designed to repair audio. It does this by approaching damaged audio by the nature of the problem, in separate “modules.” In other words, if you have a hissy, clipped recording, you first use the Declip module, then the Denoising module.

You can access these modules in the stand-alone RX app. Stereo or mono files appear in a combo waveform/spectrogram display. You attack each problem one at a time, finessing each appropriate module’s settings, one by one. You can line up multiple modules and apply them to many clips with batch processing once you’re ready, if you like.

RX also offers plug-ins that will work with your editing software. The native app I find offers more control, once you get used to it. Most of what I explain today will deal with that app.

The primary repair modules include:

  • Declip. Recovers clipped audio.
  • Declick/Decrackle. Cleans clicks, pop, thumps, and snaps.
  • Remove Hum. Strips out hum, and its ascending harmonics.
  • Denoise. Extracts hiss and noise, and sometimes other tonal elements.
  • Spectral Repair. This module repairs duration- or frequency-based slivers of audio by interpolating or “painting over” the damage with surrounding audio, or removing it completely.
  • Deconstruct. This separates tonal and noisy audio aspects, and allows you to tweak each separately.
  • Dereverb. Removes the reverberant aspect from sounds.

There are other secondary “utility modules,” such as Gain, EQ, Channel Operations, Resampling, Dither, and so on.

RX and Sound Effects

I’ve spent months inside RX struggling with difficult field recordings. Now, RX is a complex tool. It has many features. You may not touch some functions for years. Results depend on the skill and ear of the mastering technician. They also depend on the audio being repaired, say, between sound effects and dialogue.

So, for this mini review, I’ll focus on RX’s uses for sound effects field recordists. I’ll highlight the broad strokes of what’s changed between RX2 and RX3, and how that affects sound fx editors.

Are the feature differences worth an upgrade from RX2 to RX3 or RX3 Advanced? Let’s see what’s different.

Basic Changes

So, what’s changed?


The design has changed considerably. RX3 retains the dark interface, but is more modern. Modules and the edit window are cleaner, organized better, and generally easier on the eyes.


There are some interface changes:

  • RX3 Bypass Button

    RX3 Bypass Button

    A Bypass button now appears on each module. In RX2 this was accessed via a secondary click on the Preview button. Now you can compare your work with one click. Finally.

  • You can now open multiple files at once. RX2 could only open one file at a time. RX3 allows you to open 16. They’re displayed as tabs at the top of the window.

    RX3 Tabs

    RX3 Tabs

    This helps compare clips quickly. I find this helpful when working on similar takes. I master multiple (say) rock drops into separate sound files (as opposed to many takes in one long file). The tabs allow me to quickly flip through and compare the problems and results between similar tracks, and process selections of similar files. It streamlines workflow.

  • RX2 Batch Button

    RX2 Batch Button

    RX2’s Batch button has been removed from each module. That used to open up the Batch Processing window and conveniently add the foremost module’s settings. Doing the same in RX3 requires a few extra steps. That’s not hard: choose the menu File/Batch Processing, select a module under “Processing Steps,” and click the “Record” button to grab the module’s current settings. You could do this in RX2, too. RX3 omits the helpful Batch button, which I’m guessing is a way to simplify the interface. Not a huge deal.

  • RX3 - Playhead and Scrubber Tool

    Playhead Scrubber Tool

    RX3 adds a new playhead to the edit window. Dragging the playhead acts as a scrubbing tool.

  • The manual has been completely rewritten. It’s better organized, and is far more understandable and applicable than before.


Some notes about the software itself:

  • RX3 provides AAX plug-in support for Pro Tools 11+.
  • The plug-ins are 64-bit to take advantage modern computer processing power.
  • RX2 plug-ins happily run alongside RX3. This has some significance that I’ll explain below.

Power and Speed

I find the software is snappier, and smoother. It’s generally more pleasant to use, and more responsive.

I’ve only performed a few speed tests so far. When denoising, RX2 usually requires about 1.25 times the duration of a file to complete restoration. That’s when working in the “advanced tab” with the “D” setting. RX3 does the same in a third of a file’s duration.

I set tested a 30-second file with identical “D” settings in both RX2 and RX3. The result? RX2 took 49 seconds. The same file processed in RX3 completed in 9 seconds.

I’ve found RX3 is also perceptibly faster with edits, applying modules, and so on.

Module Changes

RX’s core is its modules. What changed in the upgrade to RX3 from RX2? There are many subtle changes. I’ll describe the most significant ones.

Previous RX2 Modules

  • Declip. This module quickly and effortlessly repairs clipped audio. It “just worked,” and produced impressive results. RX3 adds a cool stereo historgram. RX2 previously displayed the waveform level in a single, merged bar. RX3 separates them so you can see clips divided into left and right channels.

  • Declick/Decrackle. The largest change is the availability of click types within the Declick tab. You can now choose between a Click, Thump, or Discontinuity.

  • Denoise. This module has the most significant changes from the RX2 version. It has been vastly simplified.

    Previously, the RX2 denoise module offered two tabs: simple and advanced. Note that RX2 basic’s “advanced tab” is different than the pricey RX2 “Advanced” software upgrade. RX2 Advanced offered even more denoising options, but the basic version had a tab named “advanced” that offered a handful of critical features. (Still with me?)

    RX2 Denoise Advanced Tab

    RX2 Denoise Advanced Tab

    I hung out quite a bit in in RX2 basic’s advanced tab. In fact, I think that the tools there are absolutely essential to achieving any decent sound effects denoising results. So, I was surprised to notice that some of those tools no longer work the same way in RX3 basic. What’s changed?

    RX2 Smoothing Controls

    RX2 Smoothing Controls

    Well, first of all, the RX2 basic’s advanced tab is gone. Also, RX2 basic’s “Fine Smoothing” and “Global Smoothing” features have been removed. The “Global Smoothing” was essentially a type of “knee” for the noise profile. That determined how closely noise reduction hugged dynamic sounds. The “Fine Smoothing” tool had a magical ability to diminish “robotic” aliasing artifacts. Where are they now?

    According to an iZotope rep I emailed, everything has been folded down into the single “Artifact Control” slider in RX3 basic. According the rep:

    Artifact Control contains the smoothing parameters that were previously available, and these are included ‘under the hood’.

    It’s relieving they’re still there, however I miss control lost by merging the two tools into one. Ample control is possible with RX3’s Advanced version, but of course that’s a paid upgrade. I’d go so far as to say that if you’re planning on doing any serious denoising, you’ll need the control offered in RX3 Advanced. Again, dialogue crew, vinyl enthusiasts, and film restoration techs may have different results.

    Oh well, thankfully I can still run RX2 alongside RX3 until I spring for the $850 fee to upgrade to RX3 Advanced.

    The remaining tools from RX2’s advanced tab are still present in RX3.

    RX2 Denoise Auto-Learn

    RX2 Denoise Auto-Learn

    These are Threshold and Reduction. They are better organized in RX3’s new, intuitive interface.

    Also, RX2’s Auto Learn function has been removed from RX3. That was a helpful tool that automatically scanned selected audio for the best, cleanest noise profile. In RX3 you’ll need to track down the noise profile yourself, soldier.

  • Gain. Gain now adds a Normalize function, which was sorely lacking in RX2 basic.

    However, RX3 removed the Scan button. That detected and displayed a selection’s maximum level. I found that option helpful when adjusting gain. In RX3, you can find that info in a separate “Waveform Statistics” window found under the “View” menu item. That displays info by merely highlighting a region. It automatically updates when new areas are selected. Notice the yellow playhead in the image below. Clicking that makes the cursor jump to the point referenced.

Hum, Spectral Repair, EQ, Channel Operations, and Spectrum Analyzer remain largely the same. They’re more attractive, and more sensibly organized, though.

New Modules Introduced with RX3 Basic

What does RX3 basic add to the previous RX2 offerings? Well, three modules from RX2 Advanced have been demoted. Plug-In Hosting, Dithering, and Resampling are now available in RX3 basic.

  • RX3 Plug-In Hosting

    RX3 Plug-In Hosting

    Plug-In Hosting allows you to access Audio Unit and VST plug-ins. Not all are supported, and you can only open one plug-in at a time. However, this feature makes RX considerably more useful. Add Waves EQ or compression. Insert free VST metering software. It’s limitless. A substantial feature.

  • Dither. Another adoptee from RX2 Advanced. From the manual:

    Dithering is used to tame the quantization distortion that happens when converting between bit depths due to requantization. Dither also preserves more of the dynamic range of a signal when converting to a lower bit depth.

    RX3 Dither

    RX3 Dither

  • Resample. Offers sample rate conversion.

    RX3 Resample

    RX3 Resample

Notable Features of RX3 Advanced

RX’s Advanced version offers new, more sophisticated modules than its basic version. It also adds some additional fine-tuning options to existing modules.

In my opinion, RX2 Advanced wasn’t necessary for the common sound effects editor. RX2 Advanced offered Plug-Ins, Dither, Resampling, Time Stretch/Pitch Shift, and Deconstruct. It also offered some additional Denoising options (which some people swear by).

The story is a bit different with RX3 Advanced. iZotope shifted some plug-ins to the basic version (see above), and added some new ones. It also improved some existing modules. I’ll describe the most compelling features.

Previous RX3 Module Enhancements

  • Declip. The advanced version of Declip allows you to unlink the ganged stereo declip controls. This allows you to declip each channel at a separate level.

    RX3 Declip, Separate Levels

    RX3 Declip, Separate Levels

  • Channel Operations. One interesting option: you can now extract or remove the center of a stereo file.

    RX3 Extract Center

    RX3 Extract Center

  • Denoise. RX3 Advanced, just like RX2 Advanced, offered additional denoising options.

    RX3 Denoise, Advanced

    RX3 Denoise, Advanced

    Two supplemental algorithms are offered: advanced and extreme.

    RX3 Denoise, Algorithms

    RX3 Denoise, Algorithms

    Some aspects of RX2 basic’s missing Global and Fine Smoothing options are presented in RX3 Advanced’s Smoothing and Dynamics options. These were also available in RX2 Advanced.

    RX3 Denoise, Smoothing

    RX3 Denoise, Smoothing

    There are also Noise Floor settings: Synthesis, Enhancement, Masking, and Whitening.

    RX3 Denoise, Noise Floor

    RX3 Denoise, Noise Floor

    Most noise profiles will be static. What do you do if the noise swells or ebbs? RX3 Advanced also includes an “Adaptive Mode” that tracks changes in the noise profile over time.

New RX3 Advanced Modules

  • RX3 Dialogue Denoiser

    RX3 Dialogue Denoiser

    Dialogue Denoiser. This is a denoising tool specifically designed for speech. The major advantage is that processing occurs in realtime, and can be automated in a workstation, which benefits dialogue people greatly. I have no direct experience with this, but I know some of you have Tweeted that you’re fans.
  • Dereverb. This removes reverb from a sample.
    RX3 Dereverb

    RX3 Dereverb

    From what I’ve read on various forums people are achieving mixed results. This module faces competition from dedicated dereverb plugins (such as Zynaptiq’s Unveil ($399)).
  • RX3 also bundles iZotope’s Insight software, which has sophisticated metering tools.


Your Options

Other Denoising Options

What else is out there?

I own Waves’ Z-Noise ($500). That’s not bad. I use it for some tasks. I’ve tried SoundSoap ($150), but wasn’t a fan. I’ve used Cedar in the past. It’s dynamite, but expensive.

Some other options include Waves W43 ($200), and Noise Suppressor ($600). Those are aimed towards dialogue tasks, though.

However, RX, with its multiple tools, powerful algorithms, and ease of use outshines most competitors. RX’s price is steep ($349, and $1,199 for the Advanced version). The value for the software, however, is strong.

The Low Down

Should you upgrade to RX3?

RX3 offers increased speed under a new coat of paint. Dozens of smaller features contribute to a more intuitive workflow. Depending on your projects, these features, along with the the three new Plug-In Hosting, Dither, and Resample modules, may or may not be enough to upgrade.

RX3 Advanced is a different story. The Dialogue Denoiser, Dereverb, and additional Denoising options will have a significant impact on the quality of your restoration work.

However, don’t mistake me. Even the basic RX version will save your audio. It is powerful software, works well, and I absolutely love it. I use RX regularly when mastering my sound effects libraries. It’s extremely impressive software. The Denoising, Declipping, and Spectral Repair features are extraordinary. The Declicker is also pretty good. All tools are at least decent, and at the most, exceptional.

Every time I use RX, the tools typically recover audio I was certain was destined for the trash bin. It produces jaw-dropping results fairly easily, and only improves with experience.

New Denoising Articles

I’m currently testing RX3’s sonic improvements. I’ll follow up with an article about that soon.

In the meantime, I’ll continue with two more audio repair articles. The first will list general ideas and perspectives behind audio restoration. Then, in the final article in this series, I’ll list some specific, quick tips that newbies can use to get the most out of RX.

Want to test drive RX3? Download a 10-day demo of RX3 here.

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