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Review: iZotope RX 5

Review: iZotope RX 5
Jerry Ibbotson


15 December 2015: By Jerry Ibbotson

Jerry Ibbotson fires up the latest version of the firm’s acclaimed audio editor to see what’s new this time around.

Jerry Ibbotson fires up the latest version of the firm’s acclaimed audio editor to see what’s new this time around...

"Any chance you could fix a problem we’ve got with the sound?” It’s a phrase that makes me feel slightly faint and sick inside and normally comes from the mouth of a filmmaker or a student. Or a student filmmaker.

But I’ll let you into a secret: I actually love a bit of clean-up. I’m more of a keen amateur in this particular field. There are whole teams who work on tidying up sound every day of the week whereas it’s more of an occasional thing with me. But taking a bit of dirty audio and polishing it up is pretty damn satisfying.

When iZotope released its RX 3 set of audio tools I jumped at the chance to review it and was really impressed with the results. I’ve used it to fix a wide range of sound issues, from background hum to dodgy room acoustics, and it’s proved invaluable.

Since then RX 4 has come along, although I didn’t get a chance to play with that version. Now we’ve got RX 5 and luckily I’ve been able to get my hands on it.

What exactly is it? It’s a set of tools that can run either as VST 3 plug-ins or as a stand-alone program – a Swiss Army knife of sound-fixing widgets.

After a swift download and install, I ran into a few problems with trying to run RX 5 as a solo application. It tried to open it, but then hung before crashing out. I was using a Windows 8.1 laptop, which recently had a Windows 10 upgrade before being rolled back. This may have contributed to the problem, which I think is a display issue.

But despite uninstalling and even using Windows Restore, I couldn’t get it to work. Cue some head scratching.
That was when I switched to using it as a VST 3 plug-in with Adobe Audition CC 2015. Adobe and iZotope have a good working relationship – some of the built-in effects in Audition have in the past been iZotope products and RX 3 always worked fine in the Adobe DAW. No big surprise then that RX 5 slotted straight in with no problems.

All the right noises

Noise Reduction is the single tool in this box that I probably would use the most so let’s start there. To test RX 5’s capabilities in this area I dug out some audio files that I used on its predecessor and which have also been useful teaching tools. The first was a recording of a song called Three Cheers for Little Belgium by Violet Lorraine, which dates back to 1914 and was used as a propaganda tool in the Great War. Back in 2014 I’d been asked by a BBC friend if I could clean this up, as it was going to be used as part of the WW1 commemorations.

The sound quality, given it’s a 1914 recording, is appalling, with hiss and crackle right the way through and a warbly voice. But there’s a juicy section at the start with nothing but noise. This is key.

I fired up RX 5’s De-noiser and the interface that greeted me was reassuringly familiar. There’s a graph that represents the noise floor at different frequencies and controls for the amount of Reduction, Quality and control of noise artefacts. The De-noiser itself can run in two moves. Adaptive is basically automatic while Manual requires the software to learn what’s noise and what isn’t. I went down the latter route.

After clicking on Manual and Learn I made sure Audition’s play head was at the start of the file and hit play on the plug-in. The frequency graph responded by scrolling and changing shape, as the software was fed the raw noise. I then moved the Reduction slider to -30dB and simply hit Apply. The result was seriously impressive.

The hiss and crackle was almost eradicated, with just some residual hiss. The sound file was now perfectly useable and a vast improvement over the original. But I wasn’t satisfied so I repeated the process using the exact same settings. Where there had been a low level of hiss remaining (evident at the start of the song) there was now nothing. It was almost uncanny. I remember being stunned at RX 3’s performance on this file (the BBC producer was gob-smacked, frankly) but I would say that RX 5 goes a little further.

It’s a subtle difference but it is there. I could afford to be more brutal with the new De-noiser, without risking the dreaded ‘Space Monkeys’ – iZotope’s terms for the artefacts often left over from effects like this. RX 5 is actually so potent at noise reduction that files like this need something left in on purpose. Hearing a 1914 recording with zero background hiss is frankly freakish!

One of the other tools in the set is the Dialogue De-Noiser which, as its name implies, has an emphasis on cleaning voice material. My test audio for this was a new file, part of a Skype recording made by a BBC journalist that had the usual background ‘crud’ that this kind of material generally has. In most instances, broadcasters don’t have the time to clean it up and rate getting it on air as the top priority but I wanted to see how RX5 would manage.

Keeping it clean

The process of using the Dialogue De-noise is designed to be simple – it’s very much a no-nonsense tool. I went straight into Manual mode – highlighting a section of background noise (at least one second works best) and hitting Learn and the RX 5 play button. It makes a quick scan and then you’re good to go. Without bothering to make any further tweaks I applied the process and listened to the results.

It’s pretty obvious that RX 5 uses a gate in the Dialogue De-noiser – you can hear it gently working away in the background. But the keyword there is gentle. It’s not intrusive; I just noticed the noise level dropping to virtually zero when the interviewee stopped talking. But with the signal (the voice) at a decent level, the noise is less obtrusive anyway. Overall, as a way of quickly and simply tidying up exactly this kind if audio it does exactly what it sets out to.

My Skype recording was done – as tends to be the case – in a less than perfect environment. This is a polite way of saying it had the acoustics of a toilet. RX 5 has a tool for this: De-reverb. In my appraisal of RX 3 I’d used this on some effects I’d recorded in the field (swords in a museum spring to mind) and the results had sounded like I’d dragged the objects into a studio. With RX 5 I went down a different approach and ran the De-reverb over my Skype clips.

It’s the usual process: find a section of the file with both background sound and voice and use the Learn function in the tool. Then run the plug-in over the whole audio. The results with my Skyped interview were both subtle and noticeable. There was less ‘boxiness’ in the voice and each word was more focused and tailed-off less. I actually undid my first attempt, which left the voice a little weak, and clicked the Enhance Dry Signal box and backed off the Reduction amount a little. The result was more natural sounding and the voice was stronger.

There are plenty more toys left to play with. I ran De-click over a few voice files with spitty-click sounds (as I call them) and with some tweaking of the parameters it cleaned them up. You can even tune it to pick up on bass thumps (good for mic rattle) and points where the amplitude of the wave jumps suddenly.

De-hummer is harder to test as it needs specific electrical noise. I tried it on some fridge noise but found that the general De-noise tool worked better.

In conclusion

Overall this is a seriously impressive set of audio tools. I wouldn’t say there’s a vast difference between RX 5 and the last version I used (and which I still employ on a regular basis) but the improvements are there. The foundation of it is the De-noiser, which combines power and precision. The Dialogue tool is simple to use and would be a real bonus to broadcasters who want a swift way of tidying up material.

Okay, so I had a few problems with the standalone tool, but that’s likely to be the fault of my machine. As a VST plug-in I cannot fault it. Here’s a postscript: when researching the background to the Little Belgium song I found it on a site for historic WW1 music. There was a warning on the page about the sound quality of the 100-year-old material. Now, if they had RX 5 they wouldn’t have to worry. It’s simply a no-brainer.

Key Features

  • De-reverb for fixing dialogue recordings with too much reverb/acoustic space
  • Sync and connect with any DAW or NLE timeline using RX Connect
  • Instant Process tool allows the user to ‘paint away’ audio problems with ease
  • Module Chain to fire off all editing tasks at once

RRP: £239 (Standard), £815 (Advanced)

Jerry Ibbotson has worked in pro-audio for more than 20 years, first as a BBC radio journalist and then as a sound designer in the games industry. He’s now a freelance audio producer and writer.