iZotope RX 4 Advanced adds powerful modules — Clip Gain most appealing

iZotope’s RX 4 Advanced sound repair kit is the most advanced audio repair software available. The new version contains several new modules, among which Clip Gain, Leveler, EQ Match / Ambient Match, Dialogue Denoiser (RX 4) and RX Connect.

The RX Connect plug-in that comes with both RX 4 and RX 4 Advanced is a DAW plug-in to either analyse an audio clip or repair it. There’s one plug-in, but two different ways of working. With ProTools, you can select multiple clips and the plug-in itself is selected from the Noise Reduction category in the AudioSuite menu. In other DAWs on the Mac, the plug-in must be loaded as an AU or VST effect. I tested the plug-in with Logic Pro X found out that RX Connect isn’t even needed with this DAW. The integration with Logic Pro goes a lot deeper, as Logic supports External Sample Editors. The Logic Pro Preferences > Audio > Audio File Editor option allows you to create a menu option that sends your clips to RX 4.

RX 4 Advanced Connect

All you now need to do is select the audio file and click Edit/Open in iZotope RX 4. RX 4 will now automatically load the file for you to edit your audio. To consolidate the changes, you can “Overwrite Original File”, which saves the edit. Logic Pro X will automatically update the audio file.

The RX 4 Connect plug-in worked fine with Sony Sound Forge Pro and in repair mode I could roundtrip between the two apps, which gave me the best of both worlds, even in this Sony audio editor (which has good integration with iZotope plug-ins of its own). iZotope found a way to circumvent the monopolisation of the system’s audio drivers by some DAWs. This monopolisation prevents RX 4 from playing audio through the same audio device, but using the RX 4 Monitor plug-in should solve the problem.

One of the most important new features, in my view at least, is Clip Gain. A Clip Gain envelope allows you to adjust the gain of an audio clip over time. You can do the following with Clip Gain envelopes:

  • Fade in/fade out
  • Add nodes
  • Adjust the gain of individual nodes
  • Adjust the gain of an envelope selection.

You can start with an ‘empty’ envelope and drag points on the envelope curve as you go — visually correcting gain. However, the envelope appears populated with as many control points as necessary when you first use the Leveler module (RX 4 Advanced only) and then select the Clip Gain option from the View menu. Your workflow will dictate what you prefer, but the envelope itself being fully controllable by dragging control points really gives you an edge when quickly adjusting clipped sound or boosting parts that were recorded with gain settings that were too low.

I think Clip Gain is going to be a real boon for the video post-production crowd and especially when correcting recordings of interviews or other sounds by amateurs. As “quick-and-dirty” video journalism becomes more important, professional and dedicated sound engineers who continuously adjust recording levels are replaced. Instead, these video journalists often set their levels at some default value when they start recording and leave them at that. That value may be too low or too high for short (or longer) parts of the recording. The Clip Gain envelope then gives a very easy, very visually rich way to quickly correct for such under/over ‘exposures’.

In RX 4 Advanced, the Leveler module will automatically ride the gain to even out the variations of the signal level. The algorithm consists of a compressor with a makeup gain to achieve the desired Target RMS level. The compressor has the ability to prevent pumping on speech pauses or breathing sounds. The level detector stage includes a K-weighting filter that helps equalise the audible loudness, not just RMS level. The result is much the same as when you would be adjusting the Clip Gain envelope yourself, only much faster and in some circumstances better and more accurate and tight.

RX 4 Advanced Interface

Unlike the Loudness module, which applies a constant gain to the whole file, Leveler applies a time-variable gain. The Loudness module is great when you need your audio file to comply with one of the current broadcsting loudness rules, such as EBU R128.

Of course, the modules that were already time-savers in RX 3, are still there. Dialogue Denoiser, for example, is now available in both RX 4 and RX 4 Advanced. I’m still amazed by how accurate the automatic Dialogue Denoiser is. Of course, you can fine-tune by having the Dialogue Denoiser learn and then adjust the levels yourself, but it’s rarely ever needed.

That, by the way, is the reason why iZotope RX 3 and now RX 4 have such an appeal to professional sound engineers as well as semi-pros: the ability to automate pretty much every aspect of correcting audio and still return with a good result. Only if you need or want perfection (or because you’re having fun) will you have to spend time manually tampering with a file.

Through September 25, 2014, RX 4 will be available for $299 (Reg. $349/ €285) MSRP and RX 4 Advanced for $999 (Reg. $1199 / €919) MSRP.

The Press Release

iZotope, Inc., a leading audio technology company, has released the next generation of its industry-standard audio repair toolkit, RX. iZotope’s award-winning software transforms flawed audio into pristine, usable material by removing noises, distortions, reverb, and other common audio problems. RX 4 and RX 4 Advanced incorporate significant new workflow-optimizing functionality, leaving more time for creativity in audio and video editing. For anyone in audio post production, broadcast, dialogue editing and mixing, independent filmmaking, or music production, RX 4 can make poorly recorded audio intelligible and ready for primetime.

RX 4 Advanced is the result of iZotope’s collaboration with working professionals to identify new ways of improving workflows. They’ve translated these insights into technologies that address common needs and reflect the way people naturally want to work. New features in RX 4 move beyond audio repair—letting professionals enhance their audio.

“Audio quality is a significant concern for media workflows worldwide, spanning professionals in film and TV post production to music mixing and mastering,” says Rob D’Amico, Senior Product Manager for iZotope. “iZotope has developed an audio solution that is equally valuable in the music recording studio, post production suite, on the film set, or in your home editing setup.”

RX 4 enables users to significantly speed up their workflow through the addition of new intelligent modules, time-saving features, and deeper levels of integration with their host.

Significant new features in RX 4 include:

  • Clip Gain: Easily adjust and balance the volume of vocals and instruments with this new non-destructive editing feature.
  • Dialogue Denoiser: Reduce distracting background noise from dialogue and vocals in real time (now a standard feature with both RX 4 and RX 4 Advanced).
  • RX Connect: Streamline the editing process with a round-trip workflow compatible with industry-standard hosts.

For audio professionals in post production, music production, and mastering, RX 4 Advanced boasts additional time-saving features.

  • Leveler: Automatically balance the volume of a mix, freeing more time for creative mix decisions.
  • Ambient Match: Match the environment noise or room tone of two different audio recordings with ease
  • EQ Match: Ensure a consistent-sounding mix by matching multiple recordings with varying sonic profiles.
  • Loudness: Process whole program mixes or segments to comply with international industry standards and network-specific guidelines.

IBC attendees will be able to get their first glimpse of RX 4 at Avid Connect Europe, or catch its public debut on stage at the CPUG Amsterdam SuperMeet. RX 4 will also be available for viewing at the Avid Booth (Hall 7 | Stand J20) throughout IBC.

Users of previous RX versions can log in to their iZotope accounts at for upgrade information and special upgrade pricing.

Customers who purchase RX 3 or RX 3 Advanced after July 1, 2014 will receive a free upgrade upon release.

Both RX 4 and RX 4 Advanced can be used as a standalone audio editor or as a plug-in. Supported plug-in formats include 64-bit AAX (Pro Tools 11), RTAS/AudioSuite (Pro Tools 7.4-10), VST, VST 3, and Audio Unit

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J.D. – Copywriter – Tech. Writer – Editor at Visuals Producer – Contributor at Photoshop User, Studio Daily, POST Magazine – Sub-editor at RedShark News