REVIEW: iZotope RX 6 audio repair and restoration software

iZotope RX 6 reviewiZotope RX is the industry standard audio repair tool that’s been used on countless albums, movies, and TV shows to restore damaged, noisy audio to pristine condition. In April, iZotope released version 6 which brought the biggest ever update to the software with a new slant towards helping musicians with their audio issues, as well as plenty of improvements that continue to make the lives of post-production professionals all the more easier.

Pianist, writer and friend of Time+Space, Tony Cliff, recently took RX 6 Advanced for a test run, here’s his review, complete with some handy audio examples…

iZotope is an award-winning and innovative company developing groundbreaking audio products many of which have become industry standard. Well-known products include Ozone 7 (the powerful music mastering suite), Nectar 2 (the comprehensive vocal production suite) and the recently released RX6 audio repair suite designed for both music and post-production work.

We live in an increasingly aural and visual world nowadays where clarity of audio is expected to accompany compelling film and video visuals. More and more people are regularly podcasting or making videos recordings and these all require good quality sound to convey their meaning. Imagine the situation where you are required to interview someone but you only have access to very average equipment and this interview takes place in a noisy environment. This might well be your only chance to conduct the interview and it is not possible to do it again. Having no time for re-takes or proper checking of the interview you get back home and listen to your recording to find a horrendous amount of background noise distracting from the interview. I am sure such a scenario is quite commonplace and provides an example of where RX6 can often save your reputation and rescue your recording.


Who is RX6 designed for?
Who is iZotope RX6 aimed at then? One major market for RX6 is for anyone involved in post-production work, filming, making videos
or podcasting. RX6 has modules to cater for problems such as wind noise, lavalier mic rustle and isolating dialogue and is able to turn a problematic audio recording into one suitable for professional broadcast. You may find after your video recording session that there are issues which you did not realise at the time. To set the shoot up again may be impossible to arrange or too expensive and in such situations RX6 can prove a life-saver. Another market for RX6 is for musicians since it includes a host of invaluable modules for audio repair and enhancement such as de-essing, de-clipping, or de-bleed with the last being able to remove headphone click track bleed from a vocal recording.

Different Editions
iZotope RX6 comes in three different editions: RX Elements, RX6 Standard and RX6 Advanced. The first of these is a useful but somewhat cut down edition so I will really be discussing the Standard and Advanced Editions. The premier version has a number of very useful modules which are not in other editions including De-rustle, De-wind, Dialogue Isolate, Ambience Match, Azimuth, Centre Extract, Deconstruct, EQ Match, Leveler and Loudness. The Advanced edition also enables many useful modules to be directly available as plug-ins for your DAW in the usual formats (VST, AU, AAX) without needing to load up RX6 itself. Sometimes, however, your work may need to be carried out in the full standalone edition of RX6. In this case there is the useful RX-Connect plugin which transfers audio back and forth between your DAW and the full RX6 program for audio processing and RX-Connect is offered in both the Standard and Advanced version.



Spectrogram and Wave-Form View
Once an audio file is loaded into RX6 it is displayed in both wave-form view and spectrogram view with the midway setting showing both at the same time but you can of course choose to display more of one or the other depending on your needs. The spectrogram view often gives valuable insights into problem areas within the wave file and can often show more precisely at which frequencies problems, such as hum or noise, are occurring. There are all the usual facilities for zooming in and out within the display and of course cut, copy and paste.

The advantage of the spectrogram view is that the dominance of certain frequencies are shown by the brighter and more vivid display in the spectrogram view. This may enable you to see where unwanted sounds occur and then surgically remove them without disturbing the overall natural sound background. This type of detailed editing could typically be undertaken using the ‘Spectral Repair’ module. Whilst RX6 is an extremely powerful and sophisticated program there are numerous excellent presets available within the various modules and these may achieve your desired results with little adjustment necessary. Often a very useful technique is to use the ‘compare’ function to make a series of edited versions. Change some settings and parameters in the module and click ‘compare’ and new version of the audio is made for you to audition. This way it is easy to make five or more different versions and then compare each edit to ascertain which one has worked out best before choosing the one to use in processing your audio.

Post-Production Audio
There are many modules within RX6 and a number are clearly geared towards the needs of post-production audio for film, video and broadcasting but there are also modules which are extremely valuable within a music context or modules that crossover to be useful in almost any audio context.

The De-Rustle module is designed to correct and reduce the effects of noise produced by someone wearing a lavalier microphone and the problems of the rustle of clothes or other interference.

The De-Wind module is designed to reduce the effects of wind noise affecting a microphone especially when you may be recording outside without a ‘dead-cat’ microphone cover to help alleviate such noise. The ‘compare’ function is a very useful feature again here as you can keep making adjustments to the settings and then take the best of the selection before processing your audio.

Dialogue Isolate is another very useful module for anyone who has made an interview in a noisy environment. I tested this one out by using my iPad to record some dialogue whilst my TV was on fairly loudly in the background which distracts from the speech and I was amazed at how easy it was to achieve a much better result. You can play the before and after results in the mp3 files below.




I imagine this module will be heavily used as there must be so many occasions where an interview takes place
with distracting background noise. Ambience Match is another valuable module for post-production work. Imagine if you have scenes of dialogue some of which have a background noise and other sections have no background ambient sound. In this case the background noise may actually be providing the atmosphere you need and you want it to be consistent across all the dialogue. Using Ambience Match you simply select some examples of this noise floor then click ‘learn’ and it will add this background to the entire file so that the result is consistent.

Another useful module is EQ Match which is helpful if you are putting together sections of dialogue which have perhaps been recorded with different types of microphones. This may result in undesirable voice sound quality changes for the different microphones. With EQ Match you can tell RX6 to ‘learn’ the EQ of one microphone selection and then you can apply this learnt EQ to the other microphone-recorded dialogue. You might have to adjust the ‘amount’ settings and again you could try these different settings through the ‘compare’ function until you have reached the most consistent overall sound quality.

Another very useful module is the Leveler which is equally suitable for both music or spoken applications. In some dialogue you might have too much variation in the overall volume meaning some of the speech may not be heard properly. I tried this module out by simply speaking and every now and again I went into a semi-whisper then applied the Leveler module and the overall audio was adjusted so that the sound level was constant. Please listen to the before and after examples below…





The Leveler also has many musical uses, instrumental or vocal, and the module includes settings specifically optimised for music. This is very useful if you have a singer with less than optimal microphone technique resulting in too much overall variation in audio levels. In normal circumstances you might have to apply complicated and time-consuming volume automation throughout the track to even the sound levels out. However the RX6 Leveler can make this procedure unnecessary and it also has built in ‘Ess Reduction’ and ‘Breath Control’ if you wish. Again you can use the ‘compare’ settings to adjust various settings and then listen to the result which is closest to what you desire.

Musical Modules
I’ve been discussing some modules which benefit post-production work but there are many, just like the Leveler, which are equally relevant to music or dialogue. Another very useful musical tool is De-Bleed which can remove an annoying click-track bleed which may have found its way onto an individual vocal track. This often happens when a singer likes the drums or click track to be prominent in their headphones and maybe prefers to have one headphone side slightly off the ear thereby exacerbating bleed just to annoy the engineer!

In operating De-Bleed you will need both the vocal track and the original click track to be loaded into RX6 and they both must be the same sample rate and also time aligned. Next you select the source of the bleed and click ‘Learn’ then adjust the reduction strength in RX6 to remove the click-track bleed. It is always best to make a copy of your original audio track and work on the copy just in case and this advice really applies to any audio editing work you do. In most cases RX6 will greatly improve on the original but you might end up overdoing something and need to start over from your original recording.

Breath Control is another invaluable module where you can very easily remove or reduce breaths in either sung or spoken audio. You can adjust the sensitivity, since removing all breath will sound artificial, and there is the option to output breaths only which can be very useful to detect what you might be removing. This breaths-only output is revealing and ensures you are removing only breath sounds and not some of the singing too. Once again use the ‘compare’ function to make several edits and then choose the one which achieves your desired outcome.

Other modules helpful within a music context include the De-Click, De-Clipping and De-Crackle, De-Hum and De-Essing modules. In addition the De-Plosive is a very useful way of removing unwanted plosives typically created when singing the letter ‘p’ but also maybe letters ‘b’, ‘t’ or ‘k’.

In Conclusion
There are so many features available with iZotope RX6 that there is not enough time to discuss them all but you can download a full 30-day trial of the program. The company also offers various practice files for downloading so you can test out the ‘before’ and ‘after’ from your RX6 audio editing. Even though RX6 is a sophisticated and fully-featured application it is user-friendly in operation. Many of the presets may well fulfill most of your needs and the ‘compare’ feature is always very valuable in testing out a series of subtle adjustments to test how your audio will sound after processing. I strongly recommend that you download the free trial to test it out for yourself.

Click here to view iZotope RX6

Posted by Melanie Doidge

Having worked in marketing for over fifteen years with experience in various industries, Time+Space and the world of music production continues to be the most exciting of them all. With our brands consistently pushing the boundaries of technology with their products, the terrific DJs, Composers and Producers using them and the feedback from magazines and our customers, there's always plenty to tell the world about. Musical experience? I reached Grade 6 in piano back in my school days and am currently in the throes of trying to resurrect my abilities!


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