iZotope RX4 Advanced Review: RX4 provides a suite of cutting edge tools to enhance and repair audio. At a price that’s unparalleled for the quality of processing on offer, it is becoming the ‘go to’ restoration and post-
iZotope’s RX has recently cemented itself as the most complete, affordable audio restoration suite, combining a number of advanced audio processing tools in an easy to use interface.
Whilst this review focusses on RX4 Advanced, it is important to note that the slimmed-
RX4 requires Windows 7 (or later), or Mac OS X 10.7 (or later), and runs in standalone mode. The plug-
Installation is simple -
RX4 looks very much like an iZotope product (which is a good thing). The interface is laid out in a clear, intelligent manner with a useful dual spectrogram/waveform display taking up the large upper left section of the interface, the list of modules in a collapsible tab to the right, with the transport/metering and undo history along the bottom.
The interface is tabbed, so multiple audio files can be open at once, and switched between simply -
iZotope separate the eighteen separate processing ‘modules’ into three categories -
This area of RX4 contains tools designed to repair and restore audio in a number of ways.
Declip repairs both analog and digital clipping, according to a set threshold. Whilst this is a process that naturally involves assumptions and guesswork, the engine does a very convincing job indeed.
Declick & Decrackle are designed to remove impulse clicks, both isolated and in longer streams. Particularly useful for a variety of applications, These two modules also do an impressive job in the restoration of vinyl recordings, and in my experiments very badly
Remove Hum is a complete hum removal function. Going way beyond the scope of similar tools, in my experience, I was able to successfully eliminate a 50Hz hum signal, along with harmonics, from a particularly problematic recording using the engine here.
Spectral Repair is definitely one of the most impressive modules here in terms of what it can achieve. Using RX4’s clever display that superimposes the waveform over a spectrogram, one can readily visually identify defects in the audio and then remove the unwanted sound using a number of tools. Using the lasso tool, it is simply a matter of drawing roughly around the problematic sound, hitting ‘delete’ and the engine uses sophisticated techniques to analyse the sounds around the defect, and subsequently attenuates the problematic sound to inaudible levels (without leaving a ‘gap’ behind’). The process works remarkably -
Denoise and Dialogue Denoise both use similar engines to either manually remove background noise (by ‘learning’ from a section of the background noise in isolation) or adaptively over time, based on the engine’s intelligent noise detection algorithm.
Deconstruct is an interesting module, with a very simple interface. The idea is that a signal is separated into ‘tonal’ and ‘noisy’ components, and then the balance/gain of each can be manipulated. This can be useful for many applications -
Dereverb does just what it claims -
Leveler attempts to mimic the ‘gain riding’ process on audio, intelligently analysing the RMS to modify the gain throughout a file to level out perceived volume. Gain riding traditionally would involve manually moving the fader on the desk up and down in response to the volume of a track over time -
The ability to EQ Match is not a new thing, and it feels that here the module has been ‘bolted on’, employing a much more simplistic interface than that found in iZotope’s mastering tool, Ozone. Whilst it does the job, it does so in a limited sense -
Ambience Match is one of those tools that appears so simple, yet is so useful it is a surprise we haven’t seen it in any of the prior versions of RX. In simple terms, this can be considered a reversal of the ‘Denoise’ process -
The Time & Pitch module employs iZotopes superb Radius algorithm for time stretching and pitch-
Finally, there are a number of Utility Modules that cover a number of useful functions, from EQ and overall Gain manipulation, to Resampling and Dithering.
Whilst many of the modules are available as plugins for realtime use in the host DAW, others require offline processing, and as such there is a requirement to invoke the standalone RX4. When working within a DAW this can affect workflow, in that the file needs to be exported, the host DAW closed, RX4 opened, file processed, RX4 closed and DAW re-
Another extremely welcome addition to the bundle is iZotope’s flagship metering tool, Insight (see above). Providing comprehensive visual analysis of the audio signal, it is a perfect companion to the rest of the bundle.
Some of my work involves post-
There are a couple of negative points -
iZotope have produced an evolutionary update to RX3 here, making sensible additions without compromising the clarity and ease of use of the package. The introduction of Connect is particularly welcome for users of ProTools, and alleviates a common problem in offline processing tools such as this.
When compared with similar products, RX4 provides truly exceptional value, especially when one considers that Insight is bundled in (and would normally cost over two-