Review: iZotope RX 7

More audio restoration magic in the latest version of the essential package
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In each major update, iZotope adds unique new tools that make its RX audio repair and editor software even more powerful. RX 7, the most recent update, continues that pattern, debuting a number of key new features.

For those unfamiliar, RX 7, a standalone editor with a modular suite of repair tools — some of which are also available as plugins — comes in three versions. RX 7 Advanced has every RX feature and is where most of the post-production-related tools are found. Below that is RX Standard, which has just about all the tools that could be used for audio repair in music production. At the bottom is RX Elements, which has a much lower price but a much more stripped-down toolset.

In this review, we’ll focus mainly on the Advanced and Standard versions, which is where most of the new features can be found (see Fig. 1).

Fig. 1: In addition to a darker GUI, RX 7 introduces a number of powerful new modules and features

Fig. 1: In addition to a darker GUI, RX 7 introduces a number of powerful new modules and features

LOOKING GOOD

Cosmetically, RX 7 has been given a minor makeover. Its GUI is now a bit darker and more bluish shade of gray. Otherwise, the design is pretty much the same.

The new look provides a slightly more modern vibe and is more aligned with the look of other recent iZotope releases.

THE REPAIR ASSISTANT

If you’re new to RX, there are lots of tools to learn. To help make the repair process easier for newbies and faster for more advanced users, iZotope added the Repair Assistant to all three versions. It was developed using machine learning (a form of AI) that “taught” the Repair Assistant to detect audio problems, primarily those involving noise, clicks, hum and clicking, and suggest solutions using RX’s tools. RX 7 joins several other iZotope applications that have “Assistant” features.

To get started, you first make a selection and then click on the Repair Assistant button. You’ll get a dialog box asking if your audio is Dialogue, Music or Other. (According to the manual, Other should be used when your selection has both Dialogue and Music.)

Next, you hit the Start Analysis button, and the Repair Assistant spends some time calculating possible solutions, a process that can take only 10 seconds or so for a short segment, or close to a minute for longer ones. It’s all source dependent. The GUI tells you which of the four noise types, if any, have been detected in your audio.

When it’s done calculating, three small preview windows appear inside the Repair Assistant, each representing an alternate solution (see Fig. 2). Press the play button in each to preview your audio with the solution applied. You can also hover your mouse over the preview to see which tools were chosen and open a Sensitivity slider to vary the intensity of the settings.

Fig. 2: The four stages of the Repair Assistant, clockwise from upper left

Fig. 2: The four stages of the Repair Assistant, clockwise from upper left

Once you’ve made your choice between the three options, you press it and hit Render, and it writes it to your file. Like everything else in RX, any process is undoable (as long as you don’t save and reopen the file), so if you don’t like the results, undo them and try again.

RX also has the added feature of allowing you to open a Module Chain — an effects chain matching the tools and settings for any of the Repair Assistant’s previews — in a separate window. You can adjust the tools individually from the chain or save it for future recall.

I tried the Repair Assistant on various audio issues, including recordings with amp hum and noise, vinyl crackle, clicks and clipping. The solutions it offered, which typically involved two or three modules, were generally quite good. However, there were definitely times when I was able to manually get better results with a single tool, such as Spectral De-Noise. There was one occasion where I tried the Repair Assistant on a high-gain guitar part with a lot of amp noise, and it didn’t detect the noise at all. Perhaps that was because it’s algorithm isn’t trained for dealing with such a severe case.

Overall, Repair Assistant not only allows you to work faster, but by studying its recommendations, it also can help teach you which tools and settings work for particular audio issues.

BALANCING ACT

The new Music Rebalance module, added to RX 7 Advanced and Standard, allows you to change the relative level of crucial elements in a stereo mixed file, which is pretty mindblowing when you think about it.

When you open the module, you see four volume sliders: Voice, Bass, Percussion and Other. Other is basically everything that doesn’t fall into the first three categories. The idea is that you then start adjusting the sliders as you listen to a preview. When you’re happy with the new balance, you hit Render.

Because the plugin creates so much latency when it operates, Music Rebalance’s preview is intentionally of somewhat reduced quality. It still sounds good enough to judge rebalancing decisions, but even at the lowered quality, I found that the playback in preview frequently stopped and started, which can be distracting. Once you have the settings to where you want them, it can take several minutes to Render a song-length piece of audio, possibly longer on a slow computer.

The results are worth it, though, in many cases. It works amazingly well for adjusting the levels of the bass, drums or vocals, and you don’t hear any noticeable loss of quality or artefacts in the resultant file, especially if your moves are relatively minor. This could be a lifesaver in situations where you need to adjust a mix but don’t have access to the multitrack files.

According to iZotope, you can also use it for, say, creating an instrumental mix, or isolating a vocal track to use for a remix. For this application, I didn’t find it as satisfying. For example, when I tried to remove a vocal track from a mix completely, I still heard it faintly as well as some phasey artefacts.

The results were also a bit disappointing when removing all the instruments to isolate the vocal track for a remix. You could hear a lot of phasing and artefacts on the vocal. My takeaway is that this module is better suited for subtle adjustments than drastic ones.

I don’t want to be overly critical, because the fact that Music Rebalance can do all the things it does is really pretty astounding. It’s an amazingly powerful tool, but you must ensure to understand that it has its limitations.

VARY ABLE

Two other new modules, Variable Time and Variable Pitch, make their debuts in both RX 7 Advanced and Standard. These are not meant to replace the existing and powerful Pitch and Time module, which is designed for static adjustments. Instead, they’re for situations where you want to vary time or pitch over time.

Both modules have similar architecture: You make a selection and then can draw in a curve, in the form of a breakpoint line, that allows you to alter tempo or pitch (depending which module you’re using) up or down. I highly recommend resizing the module window to make it as large as is comfortable on your monitor, as even at its default size, the tiniest change in the curve creates a pretty significant alteration. If you want more control, it’s a lot easier to resize the screen of either module, essentially giving you more resolution.

The quality is excellent, as long as you keep the adjustments relatively minor. Both module windows offer several parameters in which to modify the results, giving you additional control. Either of these modules could be used either for corrective purposes or for something creative, such as sound design.

ADVANCED ADDITIONS

iZotope added two new dialogue-related modules to RX Advanced. One, Dialogue Contour, is somewhat similar to Variable Pitch but explicitly designed for tweaking dialogue intonation issues.

For example, say you made an edit in the middle of a sentence and the result sounded too obvious because the speaker’s intonation changed unnaturally at the edit point. You could use Dialogue Contour to adjust the pitch of the syllable or word after the edit to make it sound more like it flowed from the previous word.

The second module is Dialogue De-Reverb, which is similar to the existing De-Reverb module but its algorithm is more specifically aimed at removing room ambience from voice recordings. One way I tried it was on a recording of my voice captured about 10 feet from the mic, and I was able to get rid of most of the room tone with Dialogue De-Reverb, without adding artefacts.

MORE GOOD STUFF

If you work in post-production, you’ll be happy to know that RX 7 Advanced now supports multichannel audio, up to Dolby Atmos 7.1.2. The various channels each show up in their own lane in the RX interface and can be edited on a channel-by-channel basis or globally.

For Pro Tools users, RX 7 brings another bonus: Audiosuite versions of several of the plugins, which allow you to render the results directly to the audio file. Plugins offering this support are Dialogue Isolate, De-Rustle (Advanced version only) and Breath Control and Music Rebalance (Advanced and Standard).

PRESCRIPTION FOR CLEAN AUDIO

RX 7 brings some powerful new tools to an already loaded lineup of processors. The Repair Assistant and Music Rebalance features are the highlight additions, although people in post-production might be most excited by the multichannel support.

RX 7 crystalizes the relationship between the two top RX versions that was introduced in RX6. The Standard version is no longer second fiddle when it comes to audio repair features for music production – it’s virtually on par. Advanced is now undisputedly the version for post-production and immersive audio.

However you use RX, whether for audio repair or enhancement, and whichever version you have, the upgrade to RX 7 will undoubtedly improve your audio clean-up abilities. If you’ve never used RX, it’s worth downloading the demo and checking it out. You’ll be amazed by its power.

STRENGTHS
Powerful post-mix adjustments. Intelligent processing suggestions. RX 7 Standard virtually on par with RX 7 Advanced for music production. Two new post-prod dialog tools in RX Advanced. Multichannel support in RX Advanced

LIMITATIONS
Music Rebalance creates artefacts isolating individual elements and previews sometimes stop and start during playback. Repair assistant only covers certain issues

RX 7 Advanced $1,199
RX 7 Standard $399
RX 7 Elements $199
Upgrade pricing available

Mike Levine is a composer, producer, and multiinstrumentalist from the New York area, and is the Technical Editor-Studio for Mix.