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C.C. Hogan

Using iZotope RX 6 for Audiobooks

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I am using iZotope RX 6 Standard together with Cubase Pro to help me record and master audiobooks.

Everything being equal, you really should not need any sort of repair system when recording voice overs professionally. The studio environment should be perfect, the recording equipment should be top-line, the sound engineer should be highly experienced, and the talent should have the perfect voice.

But this series of articles I have been writing are aimed at those working from home, possibly recording only their own books, and doing everything for themselves.

Even if you have a really, really good set up, you are producing yourself, and there is no hope you are going to catch every audio glitch while you are also performing your little socks off.  That is what a sound engineer would be there for; they worry about all the technical bits from distortion to mouth slaps and have the luxury of concentrating on just those things.

This is not really a review since I am not using every aspect of RX 6 Standard and therefore not in the position to give a proper analysis, but rather it is how I am using in my own setup. My Digital Audio Workstation is Cubase Pro (currently at version 9.5), but this is similar to ProTools, Logic and other serious multi-track DAWs out there. 

Recording on these larger DAWs is not like recording in a standard WAV recorder where you are effectively creating one file.  These systems create a new file (or many files if you are recording on many tracks at once) every time you go into record.  In Cubase when you look at the Pool (the file list) you see all of them listed by track name. I give my tracks chapter numbers so my files are Chapter 01_10, Chapter 01_11, and so on. On a long chapter with loads of punch ins, I can easily create 200 files.

However, when you are working on the system, you don't even have to think about it. You just have a multi-track display with all your recordings laid out all nice and neat.

Integrating RX 6

So, How do I add RX 6 into my system to make the best advantage of it?

RX 6 Standard comes as both a standalone editor and as a series of VST plugins that work with Cubase. Two of the plugins, RX Monitor and RX Connect will get the RX 6 editor and Cubase talking to each other. This can be very useful when you are using the Module Chain which allows you to group the various plugins and use them all at once. However, I quickly discovered that this was no advantage to me, and though the connecting process has been streamlined from earlier versions, it is still clunky and requires several mouse clicks for each edit. Far too time-consuming.

But since all the modules are available as Cubase VST plugins, there is a much easier way to use the system.

My Input/Output chain

First of all, let me lay out my setup from in to out:

  1.  Neumann mic into Focusrite Saffire Pro 40
  2.  Cubase input channel with a compressor - only light compression - and a limiter for safety.
  3.  Record channel labelled by chapter - no insert plugins, EQ or other modifications. Channel outputs to:
  4.  Mono Bus. This is where a lot of the hard work goes on including EQ and some RX plugins. This is output to:
  5. Mono master out. The master channel has a Compressor/Limiter inserted post-fade and also the Apogee UV22 dithering plugin, which comes with Cubase.

This set up allows me by default to use consistent processing on all tracks and possibly forces me to be consistent in my recording and presentation.


VST plugins in Cubase can be used in two ways.

  • Inline inserted into a channel as non-destructive live processing
  • As a process plugin applied to a particular event or part of an event. (An event is a single recording - so a pretty lump on the timeline)

I am using RX 6 in both ways in my workflow.

The only other plugins I am using are the Steinberg GEQ-30 graphic EQ, the new Frequency  EQ and Limiter6 which is a very powerful and free compressor, limiter, clipper and so on. Well recommended. 

The Mono Bus

On the Mono Bus, I am using three RX Plugins plus the Frequency EQ (which is just removing very high and very low frequencies).  You will notice that the graphic EQ is currently turned off, but I have that set to remove very high and very low frequencies if I need it. In addition, I am using very specific equalisation with the powerful Frequency plugin. Obviously, this reflects my deep, old voice in particular - a nice young voice would need something different.

Voice Bus

Note, this image is a bit out of date because I have added the Waves Vocal Rider plugin to my workflow.

RX 6 Voice De-Noise

I must say I have been rather impressed with this. Because I do not have a fully insulated voice booth (next year, I have promised myself once) I wanted to make sure no noise is drifting through from hard drives and fans. This is very low level, but still a nuisance. I could get rid of this with light gating, but however well you set up a gate, it always has a negative effect on breaths, especially very quiet ones. In studios, gating is a no-no for normal voice over recording.

I fired up the De-Noise in its default Adaptive Mode and it worked a treat. The voice still sounds great, the noise has gone completely and the breaths sound lovely. Obviously, the noise problem was very minimal in the first place so it is not having to work too hard, but I am quite impressed. Other noise removal systems, like that which ships with Audition, I have found most disappointing over the years because they tend to change the tonal characteristics of the recording too much for my ears.

RX Voice De-Noise

RX 6 De-ess

I am getting older and my teeth are not what they once were, so I do get the odd sibilance problem that slips through while I am in mid-hand-waving acting mode.

Cubase actually has a very good de-esser built in, but I found this RX plugin a little more subtle which suited me.

I normally have the threshold set a little lower than the image below, but I was messing around with it. I do save presets on all of these plugins and other Cubase channel settings by the way - all called "Book something" so they are easy to find.

Although the setting will not get rid of dreadful sibilance (to be honest, that is almost impossible), it does take away a little, so I run this all the time.

RX 6 De-ess

RX 6 Mouth De-Click

This is a much better plugin than their previous De-Click for this kind of work. I use it in the chain here to catch some of those tiny little clicks. For any heavier clicks, I use the plugin in process mode just on that particular little portion of audio (see below).

RX Mouth De-Click


This was the new EQ plugin that came with the release of Cubase Pro 9. It is probably their best new feature. This eight-band EQ has allowed me to do a mix of both gentle EQ and some removal of very narrow problem areas in one go, rather than using two as I did previously. From the organisational point of view, this reduces the amount of settings I am saving, and it is also a joy to use.

The Cubase Frequency plugin

Waves Vocal Rider

I have now added #achieving-perfect-vocal-levels-with-vocal-rider" target="_blank" rel="noreferrer noopener">Vocal Rider to my bus which is at the end of the chain.

This plug in emulates a sound engineer raising and lowering the fader during quiet or loud sections. It is something we always did in the studio. This is NOT compression or Limiting! It also recognises breaths and does not raise them. A clever plugin. You can overuse it and it works best when used subtly. 


While editing, I am obviously monitoring through the output bus so I am editing in relation to any plugins, like those listed above, and any output EQ and compression. This is important as I do not want to be making changes or solving problems that will be messed up or made unnecessary by later processing. Once I have finished my editing, that is that. The result will be exported ready to be uploaded or used wherever without further processing by me.

Editing, as I have said elsewhere, is a question of both examining every part of the recording for errors, levels, timing and gaps between sentences or paragraphs, and re-recording anything I am unhappy with.  Although I do punch in when I make mistakes during the recording, I do not take for granted that the punch in is perfect. In fact, it very rarely is, not to a level I want. When I was a sound engineer (originally working on tape), I prided myself on being able to find the perfect point and manually punch into record, and could work with regular voice-overs like two musicians, getting the timing and breath perfect. However, I have found this much harder working on my own, and to keep programming up punch in points can slow me down.

With DAWs like Cubase, nothing is destroyed. Each time you punch in you create a new file. If you make several attempts at a punch in, and do not "undo" each time you mess up, you will end up with several versions with only the last version being visible (and audible). The other versions can be accessed by switching on "Lanes" in Cubase, and if you are unhappy with the final take, you can choose one of the others or just a bit from one of the others. Very useful! To be honest, I use this very little for audiobooks. Generally, it is always the final take I use and don't even keep the ones that I am never going to use.

RX 6 also now comes into play during editing.

In Cubase, plugins can also be applied as a process. If I select one event (or just a part of an event with the Range tool), I can open a plugin, preview the effect, and process just that section of the recording. This is destructive (although one can Undo, as always), so you must be sure what you are doing is right.

To make this process quicker, I have assigned key commands to several RX plugins - Mouth de-Click, De-ess, and de-Plosive. I have done these as macros so that it is a single key and after processing, the system automatically winds back a couple of seconds and goes back into play.

If I want to remove a couple of mouth clicks or smacks from a section, I simply select it with the range tool and use the key command. The RX 6 Mouth De-Click plugin opens and I can correct the problem very quickly. In fact, I have one setting that I use all the time so I don't even both to preview. I open the plugin then press Enter and it processes the part of the event and closes. Done.

I use the de-esser for removing sibilance beyond my global setting and the De-Plosive plugin in the same way.  I probably use the De-Plosive the most.

There are a couple of important notes, however.

Although these plugins are mostly transparent, they are not totally, and the Mouth de-Click, for instance, can take some of the punch out of a line and occasionally remove the odd T, which is unhelpful. So, the best way of using these is on very short sections, just enough to remove the problem. With a click, this could just be a couple of seconds long.

The other important point is that you must decide whether a repair is really the best solution. If you are also the voice over, it should be a very quick job to pop in front of the mic and re-record a line. That might be by far the better repair than trying to use a plugin, however good they are.

So, as I work through my edit, the RX plugins have become part of my natural process and the Mouth de-Click gets employed regularly.  Much of the time it is not on an actual line but in the gaps. Although it is easy to edit out clicks manually in gaps, sometimes there is a very quiet but pretty breath there too which adds emotion and timing. Removing the click will mess it up. Using the Mouth De-Click won't. So that is a result!


And once I am happy with everything, all that is left to do is output my final edit.

On Cubase, you can create more than one output channel. By default, most projects open with a stereo master, but audibooks are normally mono. Although you can create a mono down-mix on export, this can mess up your levels since it is a combination of left and right. Not good practice.

Cubase mixer with loudness meter

I create two mono masters. One is labelled ACX Master and is set up with a compressor/limiter to conform to the ACX requirements. I have this set as my default master and meter with the built-in Cubase loudness meter. 

The other is labelled YouTube master and uses the same limiter, but set up to conform to the YouTube loudness requirements instead. The bus feeds into both these simultaneously using the Cubase direct outputs, and I simply choose which output when I export. 

ACX master out

As the ACX is my default, I use this as the cue send to my headphones in the booth.

UPDATE: Since writing this article, I have replaced the two limiters below with iZotope Ozone 8 Advanced, which sounds wonderful.  I might cover using that at a different time.  However, it is not cheap, where as these two are free... 

I am using two limiters here plus the UV22HR mastering out which is the dithering thingy! 

The first limiter which is pre-fade is the George Yohng W1, which impersonates the Waves L1 mastering plugin, but is free. It is not very versatile but adds a warmth which is perfect for voice work. Not much to set up, but not needed.

W1 Limited

The second limiter is Limiter6, another free vst plugin which includes a compressor, a peak limiter (which I have turned off), a HF limiter which just catches any remaining HF nasties, a clipper that is probably unecessary here and the output protection limiter. This last is set differently for ACX and YouTube. For ACX the ceiling is a -3db whereas for YouTube it is -1db.


NOTE: I have now replaced Limiter 6 with the new version called TDR Limiter 6. This is not a free version but is a more flexible version. Worth looking up.

Because I have added Vocal Rider (see earlier), my settings are little gentler on the output now.


I am very pleased so far with RX 6 standard. The tools are powerful and useful, though I am not using all of them by any means for this type of recording.

What pleases me most is the transparency.  Any plugin, whether it is a repair tool or an effect, should only do what it says it does. It should not break the initial audio in the process. This is particularly true of repair plugins. I have not tried everything out there, but I am very happy how well the iZotope product works and it will be part of my work process for a long time to come, I suspect.

I am less happy with how the standalone editor connects to Cubase and think that could be streamlined far more. But as I said earlier, using the plugins as process plugins is much easier and is all you need most of the time. 

I will at some point look at iZotopes other tools. I am particularly interested in their Loudness tool. Loudness is incredibly important to the listener whether they know it or not, and I use the Cubase loudness meter constantly. A tool that not just measures but will actually get the loudness right for the environment is a sensible idea. Unfortunately, I can't afford it for the moment. One day...


Please feel free to comment - no anger, no bad vibes, no trashing people. Just sit around, enjoy a flagon of beer and mull over the world. You can login with Disqus, Facebook, Twitter or Google.

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