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Review: iZotope RX 6 - EMusician

Review: iZotope RX 6

A jackpot of new features for this repair-focused audio editor
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After a longer-than-usual wait between major updates, RX 6, the latest version of iZotope’s acclaimed audio repair and editing application has arrived. It offers an impressive batch of new Modules and introduces a new, lower-priced member of the RX family—RX Elements. This review will look at new features in RX 6 and point out which version—Advanced, Standard or Elements—they appear in.

MODULARITY

The RX GUI consists of the main editing window in which the audio can be viewed as a waveform, spectral display, or any combination of the two. Along the right is the Modules List, where the Repair, Utility, and Measurement Modules reside. Every version of RX can host third-party plug-ins.

You make audio selections based on time, frequency, or both, and then preview and apply the processing tool you’ve chosen. You can also setup custom Module Chains, which consist of multiple processors. Standard cut, copy, and paste functions are also available. In addition to repair tools, RX also facilitates level setting according to loudness standards (Advanced), changing time and pitch, normalizing, adjusting phase, and much more.

Among many of its new features, RX 6 provides a new way to organize the Modules List, which lets you hide unneeded Modules to reduce clutter.

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For this update, iZotope tweaked the look of the GUI, most notably in the menu area to the right. There are now so many tools available—especially in RX 6 Advanced—that they’re now organized into three categories: Repair, Utility, and Measurements. Each has a disclosure arrow, which lets you hide or show its list of tools. This feature lets you reduce the visual clutter by showing only the Modules in a particular category.

A related feature, called Module List Filters (Advanced, Standard, Elements), gives you a way to further target which menu items you see. A pull-down at the top of the main menu lets you choose categories such as Dialogue & Voice, Delivery, De-click, and more. Once selected, the menu only shows you items that are appropriate for that category. For instance, choosing De-noise shows you only Spectral De-noise and Voice De-noise.

What’s cool about Module List Filters is that you can specify your own categories, with custom Module sets. So, if you have a particular group of tools that you use a lot for, say, dialogue editing, you can put them in a set, and hide all the other tools until you need them.

Fig. 1. Four Modules were added to both the Advanced and Standard versions of RX 6: De-bleed, De-ess, Breath Control, and Mouth De-click (clockwise from top).

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RX 6 Advanced adds seven new Repair Modules. Four of the new Modules were also added to RX 6 Standard (see Figure 1). Significantly, iZotope added many of the new Modules to both the Advanced and Standard versions, which is a break from the pattern of the past.

In previous incarnations of RX, when iZotope introduced a new Module or other significant feature, it was often only included in Advanced, and wouldn’t get added to the Standard version until a subsequent major release. Although there’s still a pretty big difference between what you get in RX Advanced and Standard—especially regarding features useful for post-production—the difference between the two versions is less pronounced than in the past. If you’re using RX mainly for music, the Standard version is fairly comprehensive.

THE MOST FOR POST

Several new Modules aimed at post-production were added exclusively to RX 6 Advanced. Each is designed to eliminate or lessen specific problems that come up in dialogue recordings such as video soundtracks, radio, and podcasts. Of note, each of these Modules uses machine-learning and artificial intelligence in its algorithms. All three Modules worked as advertised when I tested them.

De-rustle removes the sound that’s created when a lavaliere mic rubs against clothing. It has a simple interface, with sliders for Reduction Strength and Ambience Preservation.

De-wind reduces or removes wind noise that gets picked up by microphones. Adjustable parameters include Crossover Frequency, for adjusting which frequencies get processed; Reduction amount; Fundamental Recovery, which resynthesizes some of the lows that get lost with the processing; and Artifact Smoothing to help reduce “Musical Noise,” a kind of distortion that makes audio sound like it’s underwater.

Fig. 2: Dialogue Isolate separates dialogue from non-stationary background noise to make it more intelligible.

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Perhaps the most impressive of the three is Dialogue De-noise, designed to reduce the constant, but non-uniform background noise (aka “non-stationary noise”) in spoken word recordings (see Figure 2). An example would be an interview recorded in a noisy public space, where the background sound partially obscures the dialogue.

Standard broadband noise-reduction tools, such as RX De-Noise, have algorithms that were created to reduce static background sounds like air conditioners. But they’re not nearly as effective when the background noise is constantly changing. Dialogue Isolate’s intelligent algorithm splits the background noise off from the dialogue and allows you to reduce it. It worked impressively well, although you have to find the right balance of settings because dialing in too much reduction can cause dropouts at the beginning and end of words.

LET IT DE-BLEED

One of RX 6’s most notable new modules is De-bleed (Advanced, Standard), which is designed to remove leakage on miked tracks. It works like this: You open the Active Track, which is the track you want to reduce the bleed on, and the Source Track, the one containing the audio that caused the bleed. Pressing the Learn button “trains” De-bleed so that it knows what to remove, and then you can use RX’s Preview feature to test the results.

If you like what you hear, hit Process and write the processing to the Active Track. If not, experiment with the two available parameters—Reduction Strength and Artifact Smoothing—until you find a better combination. The Active and Source tracks must be time-aligned for De-Bleed to work.

I tried it on an instrument track that had click bleed on it and was able to remove it without any degradation of the Active Track’s audio. I then used it to successfully eliminate leakage from a kick into a snare track and vice versa. Next, I tried it with the snare and kick from a different session, and was able to get the kick out of the snare but not the other way around. The level of success apparently depends on the individual tracks and the amount and nature of the bleed.

I found De-bleed to be a tad finicky—a couple of times it stopped working after I previewed the results multiple times, and I had to close it and start over. But it’s quite impressive overall, and it not only offers help for separating bleed in multi-mic situations but can also salvage tracks that would have otherwise been unusable due to click bleed.

ALL IN ONE

A new feature called Composite View (Advanced and Standard) lets you combine up to 16 different audio files in a single window, where they can be edited and processed as a group. For batch processing, say, multitrack drum parts, or for de-glitching a multimiked recording, it’s extremely useful.

To open Composite View, you just click its icon, and all the tracks that are currently open in RX are merged under a single editing window. There you can use most of the Modules and utilities; some, including Phase and De-Bleed, are not available.

When you’ve finished, you can export the tracks individually, with all the processing on them. I was a tad disappointed to discover you can’t export the group as one mixed file.

KICK YOUR ESS

De-ess (Advanced and Standard) is the first processor of its type to appear in any incarnation of RX and is a welcome and powerful addition. It offers two different modes: Classic and Spectral. The former uses a broadband envelope to reduce sibilance. The latter takes a more targeted approach, attenuating sibilant frequencies only where they occur, leaving the rest of the audio untouched. Based on those descriptions, it almost makes you wonder why iZotope included Classic mode because Spectral seems so much more powerful, in theory. However, in practice, there are times when Classic just works better: It depends on the source material.

Mouth De-click (Advanced and Standard) eliminates clicking and smacking sounds in vocal or dialogue recordings. I found it generally to be effective, although there were some clicks that I couldn’t get it to remove. For such situations, you can also turn to the Spectral Repair Module (Advanced, Standard), which is also good at taking out short-duration anomalies like clicks. In RX-6 Advanced, De-ess Mouth De-click, and eight of the other repair Modules also come as separate plug-ins, so you can use them directly from a DAW or audio editor.

A BREATH OF FRESH AIR

In spoken-word recordings, and to a lesser degree in sung vocals, removing or reducing breaths is often necessary. In a long-form project like a video soundtrack or podcast, it can be tedious and time consuming to manually select and reduce or remove each breath sound.

Another new Module, Breath Control (Advanced and Standard), automates that process, and can be quite a time-saver. This impressive tool works well on both spoken words and sung vocals, and it worked flawlessly in my testing. It did not create any of the dropouts that can be an unwelcome side effect of other breath-removal/reduction processors.

MORE GOODIES

RX 6 also addresses another shortcoming of previous versions, the lack of MP3 export. In both Advanced and Standard, the Export Dialog now includes MP3 as one of the options.

One of my favorite RX Modules, De-plosive, debuted in RX 5 in the Advanced version only. Now it’s also in Standard. Especially if you’re doing spoken-word editing, you’ll appreciate how well it works and how much time you save using it.

IMPROVED BUT NOT NEW

The folks at iZotope were not just content to add a bunch of new tools; they also made improvements to a number of the Modules and utilities returning from RX 5. The feature formerly known as Extract Center, which was part of the Channel Ops Module in RX 5, is now its own Module called Center Extract (RX 6 Advanced). It’s been beefed up with two new parameters: Artifact Smoothing helps reduce the artifacts that the processing causes, and Dry Mix lets you dial in a little bit of the unprocessed signal, which can help the overall sound quality.

For removing vocals, this Module did about as well as can be expected. But compared to some of the miraculous results from RX’s other Modules, it was a bit disappointing. I tested it on prerecorded material, and while the vocals were much reduced, they were still audible (probably from the reverb returns), and the overall quality of the track was degraded and a lot lower in level. In addition to reducing center-channel elements, Extract Center can also be set to lower the sides while leaving the middle.

Another notable RX 6 change is in the Deconstruct Module (RX Advanced). Previously, you could separate and adjust the tonal and noise components of a sound. Now you can also boost or cut the transients, giving you additional control.

The Module formerly called Dialogue De-noise, designed to remove background noise from vocal recordings, has been renamed Voice De-noise (Advanced, Standard, Elements). It now lets you choose whether to optimize its algorithms for sung vocals or dialogue, via a checkbox in its window.

Find Similar (Advanced, Standard, Elements), which was a menu command in RX 5 is now a full-fledged Module under the Measurements category and offers additional control compared to the previous incarnation. As you’d guess from its name, it’s designed to find similar events within an audio file, which can simplify editing. After you make a selection in the audio, you choose whether to find only the next instance of it or all subsequent instances.

There’s only one parameter in Find Similar, the Similarity slider, and it’s the key to getting good results. Set it too high, and the algorithm won’t find any matches, set it too low, and it will see almost every event as a match. Finding the right balance can take some experimentation. I tried it on a mixed drum track, and it was able to find all the snare hits. In a spoken-word recording, it was able to find all the instances of a particular word. You can even instruct it to add markers to each instance it finds, which can be super helpful.

Ambience Match (Advanced), which is useful for creating matching ambience to fill spaces in dialogue recordings has also been tweaked, offering improved matching of levels between synthesized ambience and the surrounding signal.

ELEMENTARY, MY DEAR WATSON

The new RX 6 Elements is the lowest-priced version of the RX line. It includes the standalone RX editor, with spectral editing, and four Modules—Voice De-noise, De-clip, De-click, and De-hum. It also gives you a lot of the RX Utility and Measurement Modules. Though it’s far from comprehensive, just getting the editor and Voice De-noise for $129 is a good deal, and you can always upgrade to Standard or Advanced.

SIX IS A TEN

For both RX Advanced and RX Standard, version 6 is a bountiful update, adding more new features than any previous revision. The Standard version is now a powerhouse editor/repair application for music production, and Advanced continues to be unequaled for audio repair of music, and post-production projects.

With the addition of RX Elements, as well as the top-of-the-line RX Post Production Suite 2 bundle ($1,499, which includes RX 6 Advanced, Neutron Advanced, RX Loudness Control, Insight, and free access to Pro Sound Effects and Groove3), the RX line has more options than ever before.

STRENGTHS
Elements economy version. New Modules added to Advanced and Standard versions. Dialogue De-noise and De-bleed. Composite View. Module List filters. MP3 export.

LIMITATIONS
No mixed export from Composite View. Center Extract’s results less impressive than other modules. Debleed a little buggy.

RX 6 Advanced: $1,199
Standard: $399
Elements: $129
izotope.com

Mike Levine is a composer, producer, and multi-instrumentalist from the New York area.