Audio, Reviews

iZotope RX 7 Advanced, an alternative for ADR

insight 2 surround sound

RX Advanced is iZotope’s flagship audio editor that started out as a sound correction/fixing application. A couple of versions ago, the app became a true editor with the ability to record and edit audio, and to fix, correct and adjust using a sophisticated machine learning algorithm. As with all technology, the app continuously evolves and improves, and the latest version, RX 7 Advanced, is now capable of intelligently identifying vocals, bass, percussion and other instruments in a mix. In addition, RX 7 Advanced now also supports surround sound in addition to mono and stereo.

The RX interface gives users a synthesised overview of recorded audio, with the waveform in blue on top of the sound’s spectral information. In order to understand exactly what you’re fixing or editing, you need to understand what the spectral information represents as the waveform only represents the sound’s volume. The spectrograph shows the sound’s energy, i.e. the different frequencies, harmonics, etc, that music, speech and other audio signals are made up of.

By supporting selections – even irregularly shaped ones – RX allows you to edit a sound file as a whole or across time or frequencies. In early versions, you had to always select parts for editing with the lasso, rectangle, time- or frequency-based tools yourself. With the latest version, the selection process in 99% of the cases is done by moving sliders until the app has figured out by itself exactly what you want to change. The selection tools, however, are still there for when the software falls short.

That will be in very few cases, though, as – from version 5 onwards – RX Advanced has been increasingly and stunningly accurate at selecting and correcting sound characteristics. With RX 6 Advanced, you could change music in ways that sound perfectly natural – not a hint of having it done in software. With RX 7 Advanced, you can do the same to dialogue. In fact, RX 7 Advanced is so good at correcting imperfections in recordings, in many cases you will be able to use it as a faster and cheaper alternative to ADR.

RX 7 Advanced with dialogue, an alternative to ADR

I quickly realised this when I experimented with the Dialogue Contour module. I personally have a tendency – when I’m creating a video tutorial of some app – to increase my voice’s pitch as I approach the last part but then realise I still need to add a closure. Often, that closure turns out to be totally uncalled for, at which point I find myself with an end that goes up in pitch.

The only fix is to start over again or try to create a voice-over. That’s hard to synchronise with the rest of the video without software like VocAlign or Revoice Pro. With RX 7 Advanced’s Dialogue Contour, however, I can now just lower my voice in the module and you won’t hear that it’s not recorded that way, no matter how hard you try.

With RX 7 Advanced, you can also isolate or remove dialogue or vocals from music. When, for example, in a video of a restaurant with background music the dialogue is hard to hear, you can fix that with Music Rebalance. It also allows you to create instrumental (or acapella) versions of songs by removing the vocal elements and isolate the vocals from the background music. I had my doubts with this, but after trying it out myself with different settings I am truly astonished that it works so well. I could even isolate Cecilia Bartoli’s voice from the violins in an aria on The Salieri Album CD. Admittedly, with the default setting, there was a tiny bit of bleeding from those violins in her voice, but a bit of experimenting with the slider delivered a pure vocal signal.

De-Reverb is a module that has been available in RX Advanced for some time, but now there’s also Dialogue De-Reverb for removing unwanted reverb from dialogue clips using an algorithm optimised for a “spoken signal”. I tried that with a recording of an announcement over the intercom by a museum guide in a cathedral. That didn’t work because the signal was 99% reverberation. However, speaking myself in a microphone in that same cathedral worked much better than I could have imagined. This module too could be used in place of ADR.

Surround sound

RX 7 Advanced now also supports 7.1.2 multichannel surround sound. It lets you work on multichannel projects by toggling between all channels in one view or displaying a summed view. You can also turn individual channels on and off, summing only the ones you want to work on.

Finally, iZotope’s RX 7 Advanced has what they call assistive audio technology. This module is an intelligent repair advisory tool that can detect noise, clipping, clicks, and more. It’s designed to speed up correction and edits as all you need to do is select the type of material (music, dialogue, other) and let RX 7 Advanced analyse the audio. The Repair Assistant then offers different suggestions for processing, using multiple modules, as well as three different intensities for each. Your task is reduced to reviewing and auditioning, hitting “Render” and let Repair Assistant perform its magic.

I found the Repair Assistant to be really helpful with certain audio files and less so with others. Unfortunately – and as far as I could see – there’s no fixed rule to determine if files are suitable to run through the Repair Assistant or not. The only rule I could deduct was that, if the audio has many sudden, unexpected artefacts that sound like they’re really part of the signal you want to rescue, Repair Assistant sometimes isn’t going to cut it – yet. I expect it to keep improving in future releases, though.

Insight 2

Besides RX 7, iZotope also upgraded its audio analysis tool, Insight. Insight 2 works in tandem with an iZotope plug-in, Relay, that allows you to analyse the interaction of two or more tracks or channels with the track you’re analysing. If you insert an Insight 2 instance on the Master track, you can analyse up to eight different tracks upstream.

Insight 2 by itself has been hugely improved with the addition of a couple of new features. For example, the Intelligibility module allows you to measure whether your dialogue mix holds up in different listener environments. With the Intelligibility meter inserted on the master track, you can ensure that a dialogue is clearly understandable in low, medium and high noise environments. How those are defined remains somewhat obscure, although it does work as you’d expect. The meter requires that a Relay instance, which is inserted on a track or bus that feeds into the master output, be selected as the Source instance.

Another module that can tap into the Relay feature is the Spectrogram – 2D or 3D – which provides a spectral representation of audio varying over time, allowing you to analyse individual elements within a mix. It can display data for up to eight sources simultaneously by selecting Relay instances in the source selection menu.

As with RX 7 Advanced, Insight 2 supports surround sound. For example, you can monitor the loudness of your surround sound mixes with support for Dolby Atmos 7.1.2 track configurations, but you can also monitor the surround sound field with a surround scope that shows the amplitude of surround channels. The Surround Scope not only monitors the phase relationship between neighbouring audio channels but also displays an alert when there is a negative correlation or phase cancellation taking place.


The RX 7 Advanced upgrade focuses on the human voice in both musical and noisy environments. It succeeds brilliantly at extracting vocal signals for you to manipulate. The vocal capabilities of RX 7 Advanced are so good that you can use modules in RX 7 Advanced to fix dialogues instead of replacing them and perform complex and usually expensive ADR.

Both with RX 7 Advanced and Insight 2 the big news is that the apps now support surround sound, which makes them much more suitable for cinema and video audio besides music. Combined with the rather spectacular results you may expect from the machine learning algorithms, there now are numerous cases which you don’t really need an experienced sound engineer for anymore.

In short, both apps deserve at least a closer look – a demo download is available – after which I think you will find them both must-haves.