Module & Plug-in

Overview

Spectral De-noise is designed to remove stationary or slowly changing tonal noise and broadband hiss by learning a profile of the offending noise and then subtracting it from the signal. It can be useful for tape hiss, HVAC systems, outdoor environments, line noise, ground loops, camera motors, fans, wind, and complex buzz with many harmonics.

Spectral De-noise learns a profile of the background noise, then subtracts that noise when a signal’s amplitude drops below the specified threshold. It is a flexible tool that can be used to quickly achieve accurate, high-quality noise reduction. It also provides separate controls for tonal and broadband noise, management of denoising artifacts, and an editing interface for controlling reduction across the frequency spectrum.

Controls

  • LEARN: When Learn is enabled, Spectral De-noise will capture a noise profile from your selection. After a noise profile is captured using Learn, it remains fixed for the duration of processing. Manually learned noise profiles are best suited to removing or reducing noise that is constant and continuous throughout the duation of the file.

    How to Learn a noise profile in Spectral De-noise

    • Make a selection of the longest section of noise you can find in your file (ideally a few seconds in length)
    • Click the Learn button to capture a noise profile.
      • To capture a noise profile in the RX Audio Editor Spectral De-noise module, make a selection and click “Learn”
      • To capture a noise profile in the RX Spectral De-noise plug-in, engage the Learn button and playback audio, OR choose “Preview” in Audiosuite to capture the noise profile from your current selection.

    More Information about Learning Noise Profiles

    • See the More Information section below to learn more about getting the best results when capturing a noise profile and Learning a noise profile from multiple selections in the RX 6 Audio Editor.

  • ADAPTIVE MODE: When Adaptive Mode is enabled, the noise profile used for Spectral De-noise processing will change based on the incoming audio. Adaptive mode can work well with noise sources that are constantly changing, like recordings in outdoor environments, traffic noise, or ocean waves.

    Spectral De-noise Adaptive mode Performance Note

    RX Documents can only be opened in the RX Audio Editor. If you need to save your file so it can be opened somewhere else (like a DAW or media player), you need to export it in another format (like WAV or AIFF). To save an RX Document, select File Save RX Document and select where you would like. Closing a file. There are two ways to close a file: Close: if you close a file that has uncommitted changes (represented by a dot or asterisk next to the file name in the tab display), RX will ask you if you want to save the file. RX does not ask about saving files when the application is closed because your changes are retained in its session data. How to Use Music Rebalance in RX 7 Sep 13, 2018. Isolate mix elements from a single track with the new source separation module in RX 7, Music Rebalance. Easily reduce vocals in background music for clearer dialogue, learn how to remove vocals from a song, or separate vocal stems from a track for easy remixing. Preserve Non-Audio Data-When enabled, this feature preserves additional data in your audio file, such as cue points or ACID-ized WAV information. While both versions of RX feature basic MBIT+ dither on export, iZotope RX Advanced also features a special Dither Module which allows full. Some dialogue problems can’t be fixed. Distortion, errant sirens, wind gumming the microphones—it’s impossible. The truth is, with iZotope RX, you can fix all sorts of previously impossible problems. Here are six tips to get you out of a dialogue bind. Auto save data for izotope rx location.

    • The Adaptive mode in Spectral De-noise uses a significant amount of memory and computational power. For a more efficient form of adaptive noise reduction, try the Adaptive mode in Voice De-noise, which is designed to be highly efficient and zero-latency.

  • LEARNING TIME [s]: Determines the amount of lookahead time used by Adaptive mode when learning noise profiles that change over time.

  • THRESHOLD (NOISY/TONAL): Controls the amplitude separation of noise and useful signal levels.

    • Higher threshold settings reduce more noise, but also suppress low-level signal components.
    • Lower threshold preserves low-level signal details, but can result in noise being modulated by the signal. Threshold elevation can be done separately for tonal and random noise parts. A good default is 0 dB.

      Tip

      • If background noise changes in amplitude over time (like traffic noise or record surface noise), raise the Threshold to accommodate for the changes.

  • REDUCTION (NOISY/TONAL): Controls the desired amount of noise suppression in decibels.

    • Spectral De-noise can automatically separate noise into tonal parts (such as hum, buzz or interference) and random parts (such as hiss). You can specify the amount of suppression for these parts separately (e.g. in some situations it can be desirable to reduce only unpleasant buzz while leaving unobjectionable constant hiss). Strong suppression of noise can also degrade low-level signals, so it is recommended to apply only as much suppression as needed for reducing the noise to levels where it becomes less objectionable.

  • QUALITY: Affects the quality and computational complexity of the noise reduction. This selection directly affects CPU usage. RX’s Spectral De-noise module offers four algorithms that vary in processing time.

    • A: is the least CPU intensive process and is suitable for real-time operation. It reduces musical noise artifacts by time smoothing of the signal spectrum.
    • B: achieves more advanced musical noise suppression by using adaptive 2D smoothing (both time and frequency). It is more CPU intensive and has more latency, but can still run in real-time on most machines.
    • C: adds multiresolution operation for better handling of signal transients and even fewer musical noise artifacts. It is a very CPU intensive algorithm and can only run in real-time on faster multicore machines.
    • D: adds high-frequency synthesis for reconstruction of signal details buried in noise. The speed of algorithm D is similar to algorithm C.

  • ARTIFACT CONTROL: Determines how much noise reduction will depend upon either spectral subtraction or wide band gating.

    • With lower values, noise reduction will rely upon spectral subtraction, which can more accurately separate noise from the desired audio signal, but can yield musical noise artifacts, resulting in a “chirpy” or “watery” sound during heavy processing.
    • With higher values, the noise reduction will rely more heavily upon wider band gating which will have fewer musical noise artifacts, but sound more like broadband gating, resulting in bursts of noise right after the signal falls below the threshold.

  • NOISE SPECTRUM DISPLAY: The Noise Spectrum display shows useful information during both playback and when the noise reduction process is being applied.

  • NOISE SPECTRUM COLOR LEGEND:

    • Input (Gray): spectrum of input audio signal
    • Output (White): spectrum of the denoised output audio signal
    • Noise Profile (Orange): the learned noise profile plus offset from the Threshold control
    • Residual Noise (Yellow): desired noise floor after denoising, can be controlled by modifying the Reduction Curve
    • Reduction Curve (Blue): manual weighting of the noise reduction across the spectrum

  • REDUCTION CURVE: When enabled, allows for fine tuning of the reduction spectrum with up to 26 edit points. This enables you to customize the amount of noise reduction being applied across different frequency regions.

    • Higher edit point values result in less noise reduction in the associated frequency region.
    • Lower edit point values result in more noise reduction in the associated frequency region.
    • For example, if you wanted to reduce some low HVAC rumble but preserve some energy in higher frequencies, you could drag the curve’s leftmost point down a little bit, then create a point around 5 kHz and drag it up a bit.

      Interacting with the Reduction Curve Edit points

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      • Add an edit point: left-click, displayed as gray box along envelope curve
      • Remove an edit point: right-click or drag it outside the screen
      • You can axis-lock reduction curve points by holding Shift while dragging them, and get very fine control over positioning by holding Control/Command.

  • SMOOTHING: When the Reduction Curve is enabled, this controls the amount of interpolation between your reduction curve points, allowing for sharper or more gradual slopes between edit curve points.

Noise-reduction Software Mac/PC. But unlike its Wave Arts and Sony Oxford counterparts, the RX plug–in left some high–frequency buzz behind, even with all eight harmonics in circuit. However, on the 'Tape Motor' test file, RX Denoiser was actually the best of the bunch, with a slightly cleaner sound than any of the others. Mouth clicks and lip smacks are a common problem for dialogue editors. IZotope RX introduces a new module for their automatic reduction—Mouth De-click.In this article, Alexey Lukin, the developer of Mouth De-click, describes how it works and what makes it different from other declickers. How Declickers Work. To understand how declickers work, it's helpful to first think about classifying. May 18, 2017  Once you’ve downloaded the two test files for this tutorial from the RX webpage, one called “Male Click,” and the other, “Female Click,” and opened them in RX 6 by dragging them into the RX application window, or by opening RX and pressing Command+O, or Control+O on a PC to locate and open the files, your RX window should look like.

Controls: Advanced Settings

Algorithm Behavior (Advanced Settings)

  • SMOOTHING: Controls the reduction of musical noise artifacts which can be a result of heavy denoising.

    What is musical noise?

    • Musical noise is caused by random statistical variations of noise spectrum that cause random triggering of sub-band gates. These artifacts are sometimes described as “chirpy” or “watery” sounds left behind during the noise reduction process.

  • ALGORITHM: Selects the smoothing algorithm for the removal of random ripples (“musical noise” artifacts) that can occur in the spectrogram when processing your audio. The strength of smoothing is controlled by the Smoothing slider.
    • SIMPLE algorithm: Performs independent noise gating in every frequency channel of FFT. Release time of sub-band gates is controlled by the Release slider. This is a fast algorithm with low latency that is suitable for real-time operation.
    • ADVANCED & EXTREME algorithms: Perform joint time-frequency analysis of the audio signal which results in better quality and fewer “musical noise” artifacts. These algorithms have higher latency and computational complexity.
  • FFT SIZE (ms): Selects the time and frequency resolution of the processing.
    • Higher FFT sizes give you more frequency bands allowing you to cut noise between closely spaced signal harmonics, or cut steady-state noise harmonics without affecting adjacent signals.
    • Lower FFT sizes allow for faster response to changes in the signal and produce fewer noisy echoes around transient events.

      Re-learn your Noise profile if you change FFT size

      • Whenever the FFT size is changed, it is recommended that you run the De-noise module’s Learn feature again because the old noise profile was taken at a different FFT size and therefore becomes inaccurate.

  • MULTI-RES: Enables multi-resolution processing for the selected algorithm type.
    • When you select the Multi-res checkbox, the signal is analyzed in real-time and the most appropriate FFT size is chosen for each segment of the signal. This is done to minimize the smearing of transients and at the same time achieve high frequency resolution where it is needed.

      Note

      • The FFT size control does not have any effect in multi-resolution mode as the FFT resolution is selected automatically. The noise profile does not need to be re-learned when switching to multi-resolution mode.

      What is an FFT?

      • Fast Fourier Transform: a procedure for the calculation of a signal frequency spectrum. The greater the FFT size, the greater the frequency resolution, i.e., notes and tonal events will be clearer at larger sizes. However, when using FFT-based processing, the more audio you remove from your source, the more likely you are to create undesirable artifacts.

Noise Floor (Advanced Settings)

  • SYNTHESIS: Synthesizes high frequency material after denoising.
    • When Synthesis is set to a value greater than zero, signal harmonics are synthesized after denoising. The synthesized harmonics remain at the level of the noise floor, and serve to fill in gaps in high frequencies caused by processing.
    • Increasing Synthesis can increase the sense of life and air in processed audio. Too much Synthesis may cause apparent distortion in the signal.
  • ENHANCEMENT: Enhances signal harmonics that fall below the noise floor.
    • Enhancement predicts a signal’s harmonic structure and places less noise reduction in areas where possible signal harmonics could be buried in noise. This aids in preserving high-frequency signal harmonics that may be buried and not detected otherwise.
    • Enhancement can make the resulting signal brighter and more natural sounding, but high values of harmonic enhancement can also result in high-frequency noise being modulated by the signal.
  • MASKING: Reduces the depth of noise reduction where you wouldn’t perceive any effect from it.
    • Masking enables a psychoacoustic model that dynamically controls suppression amount to facilitate the use of softer suppression where noise is subjectively inaudible. When noise in certain regions is calculated to be inaudible, this feature prevents any signal processing in these regions. This potentially reduces the amount of processing done to the signal and may positively affect overall signal integrity. The position of the slider controls the influence of psychoacoustic model on suppression levels.
    • If you need to cut very high, inaudible frequencies, set this to 0. Otherwise, leave this at 10.

      Note

      • When the Masking slider is set to 0, the feature is turned off, and the amount of noise suppression is uniformly governed to the yellow curve in spectrum analyzer (more precisely — by the difference between the yellow curve and orange curve).

  • WHITENING: Shapes the noise floor after processing to be more like white noise. Whitening modifies the amount of noise reduction (shown by the yellow curve) applied at different frequencies to shape the spectrum of the residual noise.
    • When Whitening is set to zero, the suppression is uniform at all frequencies, as controlled by Reduction (tonal/broadband) sliders, and the suppressed noise has a similar spectral shape to the original noise.
    • When Whitening is set to the maximum value, the desired shape of suppressed noise floor is made close to white noise, so that residual noise has more neutral sound.

      Understanding the effect of the Whitening control

      • Changing the noise floor balance with Whitening can help prevent gaps from over-processing, but an unnaturally white noise floor can introduce problems like noise modulation when editing or mixing with other noises from a unique space (like a set location.)

Dynamics (Advanced Settings)

  • KNEE: Controls how surgical the algorithm’s differentiation is between the signal and noise. This slider controls the sharpness of the gating knee in the denoising process.
    • At higher values, transitions in the De-noise are more abrupt and can become prone to errors in the detection of the signal with respect to the noise.
    • At lower values, the denoising becomes more forgiving around the knee, and applies less attenuation to signals that are only slightly below the threshold. This may result in a lower depth of noise reduction, but can also have fewer artifacts.
  • RELEASE [ms]: Selects the release time of sub-band noise gates in milliseconds. Longer release times can result in less musical noise, but may also reduce or soften the signal’s initial transients or reverb tails after the signal’s decay.

    Note

    The Release control is only available when the Simple algorithm is selected.


More Information

Tips for getting the best results when learning noise profiles manually

  • Before learning a noise profile, identify and select the longest section (ideally a few seconds in length) of the recording that contains only the noise you wish to remove or reduce.
  • To ensure the best results, your selection should not contain any content that you wish to preserve (for example, do not include any audio you do not consider to be “noise” in your selection.)
  • Usually you can find noise only sections at the beginning or end of a file, or during a pause or break in the recording (for example, a pause between words in dialogue recordings.)

Learning a Noise Profile From Multiple Selections

In the RX standalone application, it is possible to create a spectral profile from multiple isolated selections. This is useful when you have a file where it’s impossible to find enough isolated noise to build the profile.

For example, if you are trying to restore a file where someone is speaking over noise, you can select noise in frequencies where none of the voice is present at a given time. If you select enough of this noise with the Lasso or Brush selection tools, you can create an accurate noise profile that will give you good results with Spectral De-noise. You can create more than one selection at a time by holding Shift and making a selection.

Select noise anywhere you can to build a better noise profile.

This feature is not available in the Spectral De-noise plug-in because it requires using RX’s spectral selection tools as well as accurate calculation of the time and frequency of the selected areas.

If you are unable to create a full noise profile with multiple selections, RX can try to build a reasonable noise profile out of your existing profile. If you have an incomplete noise profile, RX will ask you if you want it to complete the profile.

For example, if you can only capture a low frequency rumble below 100 Hz, some broadband noise between 200 Hz and 5000 Hz, and all the noise above 8000 Hz, RX can fill in the gaps for you.

Building a profile from multiple selections gives you some flexibility,
and RX will guess any noise you missed.

  • Sound Quality
  • Ease of use
  • Features
  • Bang for buck
  • Overall:
  • Software: RX 5 Advanced Audio Editor
  • Developer: iZotope
  • Formats: Standalone application, VST, AU and AAX plug-ins for Mac and Windows.
  • Price: Standard Version $349 - Advanced Version $1199 (US Dollars - MSRP)
  • Demo: Fully functional for 14 days
  • DRM: iLok (USB dongle not required)
  • Website: https://www.izotope.com/en/products/audio-repair/rx/

Preamble
Having a set of audio repair tools is definitely one very desirable in most studios and on some they are just mandatory - any serious post-production facilities and mixing or mastering studios are bound to deal with damaged audio at some point. With that in mind, the question is: which one to choose? Fortunately for us this segment shows a busy yet not crowded marketplace, with a handful of great sounding and very capable solutions competing for attention but far from the over-saturated equalizer and dynamics segments. Having said that, the fact that not many developers put their efforts on making audio repair tools can be attributed to some extent to iZotope RX’s existence. Released back in 2008, RX simply took over. With an effective and powerful set of tools of the highest quality and a straightforward editor, iZotope pretty much dominated the market and although there are still some good competition out there, it’s safe to say that RX became a reference. We’ll go through it’s fifth iteration to see how far it goes in 2015 and if it manages to keep its crown. I’ll try to break down the editor’s major features, then do a brief run on the modules to wrap it all up in the end with scores.
The RX Audio Editor
RX’s audio editor features a clean layout with a very nice waveform and spectrogram display that can be customized to blend both visualization modes, offering a great deal of information about the amplitude and frequency of the audio material in place. The editor also features a clip-gain line, which provides very easy gain adjustment of the audio before it hits the modules. Right-section of the interface houses the modules - which I’ll go through in a moment and visualization options for frequency and amplitude. Lower section provides scrolling, further visualization and zoom controls, and the tools you need to select amplitude, frequency or time of the material and also a instant-process button that applies de-click, attenuate, fade, gain or spectral repair (replace) based upon common-use presets. This greatly speeds up the workflow and helps a lot if you’re dealing with lengthy material that needs a ton of small adjustments. Used in conjunction with the lasso tool it greatly straights up the process, allowing for quick repairs on the highlighted frequency, amplitude and time regions. Selection a region and right-clicking on the selection also brings up useful operations such as capturing the required frequency and amplitude information to feed specific modules that are based on frequency/amplitude “learning” functions such as EQ and Ambience match and De-noise. RX can also do audio recording with monitoring, which is good when doing restoration and archiving work since you can capture the material and keep everything within RX right from the very beginning. RX also comes with WAV, AIFF, FLAC, OGG import/export codecs so all bases (minus Apple codecs) are pretty much covered.
The RX modules and the Module Chain
Before I go through each module, I’d light to highlight one of the coolest RX features, the Module Chain, which lets the use combine multiple RX modules, providing a quick way to process audio with module-combos that you already know will work. I should mention that that the De-clip, De-click, De-crackle, De-hum, De-noise, De-Reverb and Dialogue De-noise modules are also offered as standalone as standalone plugins for your DAW, albeit at the cost of considerable latency and CPU resources on most cases. Nevertheless, it’s a welcome alternative to using the editor when you really need to deal with something live and/or with varying settings.
  • De-clip: RX’s tool to deal with distortion problems is absurdly good and does some miracles on even the hottest and most clipped recordings you can come across. The layout is very intuitive and hard to get wrong, with some visual aid on the material’s amplitude, so it’s just a matter of setting the clipping level you want to address with the threshold slider and be amazed by the results! De-clip also features an optional make-up gain control and a peak limiter to keep things safe. Arguably one of the useful tools in RX’s arsenal and one that will likely get a lot of use when your sources are less than ideal, De-clip is a life saver. I found that applying it multiple times instead of going for a huge hit leads to better results and I couldn’t believe most things I was doing! Please ponderate my excitement a little bit and keep things in context within reason - this module will not save badly clipped mixes on a mastering situation, although it can definitely make them a lot more bearable and workable.
  • De-click: Another miracle-maker, the De-click module can do a hell lot more than just plain click-removal. Along with the De-plosive module this is one of the best tools to deal with problematic sounds from syllables with “Ps” and “Bs” - just set the click type to “thump” and make things right! When used for it's meant purposes, it is simply the best solution I’ve found to this day to deal with a lot of flexible options to deal with all sorts of clicks, crackles, thumps and all sorts of short-bursts of crappiness that might’ve plagued a recording. I got very effect results using the frequency skew to nudge it towards low or high frequency attenuations and with the click widening options, which set operating length in milliseconds for the processing. It’s so effect that it’s scary, and it manages to remove the undesired and only the undesired, leaving the rest of the content rather untouched. A real lifesaver that could very well be a plugin on its own without any fear of the competition.
  • De-hum: A set of notch and high-pass filters for cutting out electrical noise. The notch filters can act as cut-only parametric bands and the high-pass filter also features a variable slope, so in that regard De-hum can serve as general purpose and simple to use equalizer with all the quality one expects from iZotope.
  • De-noise/Dialog De-noise: Another one that could definitely be a plugin on its own and it would be a very competitive entry in the noise-reduction segment. Extremely effective and versatile, coming in two operating modes: a broadband mode with the entire frequency spectrum and dialog/speech mode that is optimized for the frequency range of a human voice - this last mode also reveals itself as an excellent tool for removing or attenuating hiss from any kind recording, not only dialog. In that regard, I’ve found myself using Dialog De-noise a whole lot more since most of my noise problems occurred in the top end and on few occasions I had to resort to the full-spectrum mode.
  • De-plosive (advanced only): This is a tool catered to the removal of the sounds associated with the excessive air coming from the Ps, Bs, Ts, Ks of the human voice that hurts microphones so much, especially on close-proximity situations. Very effective when used in conjunction with the De-click, the De-plosive can do wonders for a vocal track, setting up the terrain for the mixing stage, and needless to say that it is also great for cleaning up speech when pristine edits are needed.
  • Spectral Repair: One of the most advanced (if not the most) module on RX, this tool provides cutting-edge processes to remove unwanted elements of the material such as footsteps, old chairs squeaks, mouth-related artifacts, buzzing alarms in the background and other noises and interferences that are happening at the same as the audio you want to use. Spectral Repair acts both on frequency and amplitude domains and it’s very effective when used along with RX’s impressive zooming features and the lasso tool also works wonders for precise selection of the audio to be processed. It can do attenuation of the undesired and also replace it altogether with the surrounding material, which is specially useful on polishing solo recordings of acoustic guitars, close-mic'd strings and vocals, taking the trash out without hurting the content. Spectral Repair can only process a small bit of material so it is a laborious yet ultimately rewarding task that can save bad recordings but also take good recordings to near perfection.
  • Deconstruct (advanced only): Along with Spectral Repair, Deconstruct is one of the hardest tools to understand and master despite its limited of controls. It breaks the audio to “tonal” and “noise” components, allowing you to dial the amount of each one, radically changing the sound of a recording. Simply put, this module lets you isolate background noises on a musical recording or just take the music away and leave the noise, to some extent at least. Very interesting module to play around and learn what it considers as tonal and noise - also a good way to deal with the desired-undesired balance when Spectral Repair failed to achieve the desired results.
  • De-reverb: Now available on the standard version, the De-reverb module is one of RX’s finest tools. With a simple and uncomplicated layout, De-reverb has a powerful “learn” function that reads the incoming audio and splits what it considers to be the reverberant components so the user can adjust the amount of reverb through 4 bands dry/wet bands that covers the frequency spectrum (low, low-mid, mid-high, high). There’s also a couple of handy functions such as the “enhance dry signal” that further mitigates the reverb and the tail length adjustment which is great when you don’t want to take everything away.
  • Leveler/Loudness (advanced only): Leveler almost feels like cheating. It’s basically a gain-rider that works with the..rider! Set the target RMS and let it do its magic. Loudness is Leveler on a “static mode” i.e. no gain riding, so it just sets levels according to seven loudness standards adopted by the industry, which is good for quick conversion jobs where you just have to send finished audio to a client that asked for some specific loudness standard. They’re also very useful when adjusting lengthy material. I’ve some documentaries in the past where I had to deal with tons of different recording situations and Leveler would save me a ton of time on pre-editing - definitely looking forward to the next gig, it will get some good use.
  • EQ Match (advanced only): I was introduced to iZotope’s EQ matching technology on Ozone and for music production it was never a technique that I used frequently, or to be totally honest I almost never use unless a job really requires it. In theory you capture the overall frequency spectrum of a recording and apply that EQ curve to another recording, resulting in a more-or-less similar spectral content. Not something I’d want often when doing music production, although I know of some cabinet-emulation freaks that make good use of this technique. However, things were different with RX, largely due to the very nature of the works I’ve done with it and the overall focus of the application. In that regard, EQ match delivers very good results with minimum effort. It’s interface is dead simple and the process revolves basically around “learning” the spectrum from one audio region and applying it to the other. This module proves to be very useful for dealing with the situation I described above on my comments about the Leveler: it’s great to homogenize radically different audio recordings. Coupled with Leveler and Ambience match, EQ match is great to nudge a sound into the direction you want. Nevertheless, this is something that operates within obvious constraints and you’ll not turn a recording around 180 degrees, but you can definitely help it sound more coherent, adding to the overall cohesion of the program material.
  • Ambience Match (advanced only): Similar in principle to the EQ match, but more ambitious in its scope, Ambience match tries to make the acoustics of different recordings more close to each other. Just like it’s EQ sibling, Ambience Match is very simple to use - capture one area’s ambience and apply it to the desired target, and just like EQ match it is also great to level out differences in recording when homogeneity is required.
  • Time & Pitch* (*pitch contour - advanced only): As the name says, this module can do time and pitch adjustments and they can be linked or unlinked to each other. The guys at iZotope have a fair share of expertise here since the Radius days and it’s not different this time around.
  • Plugin: A plugin host so the user can have their favorite Audio Units and VSTs inside RX. The only problem here is that the plugins are not capable of running on real-time and will act like RX modules, which means you have to use the preview function to listen to the changes before committing to them. Nevertheless a very useful feature despite all shortcomings of offline processing.
  • Gain: As the name says - plain gain adjustment for your volume needs. It has to be here although a bit redundant since you can use the clip gain line to make fine gain adjustments at the pre-module stage, but Gain comes in handy for the post-module processing adjustments and it is also useful with the module chain.
  • Corrective EQ - Easy to use and very effective, this is basically the proven and reliable Ozone equalizer minus the matching and real-time frequency analyzer functions. This equalizer provides six parametric filters and low/high pass filters and operates on both linear and minimum phase. It sounds very pristine, with superb accuracy, a real text-book implementation. Very good to have within the context of audio repair suite.
  • Channel Ops (azimuth and extract center - advanced only) - A utility module to adjust the stereo field, allowing the user to raise/lower left or right channel, along with phase and azimuth adjustments. There’s also a “extract center” function to isolate mid from side on stereo recordings.
  • Resample - This module provides sample rate conversions using one of the cleanest algorithms out there (according to this huge and ever-increasing database SRC Comparisons), with a special steep low-pass filter developed by iZotope to keep aliasing away.
  • Dither - Last but not least, dithering for your bit-reduction needs with all the necessary options one needs to safely convert with the best quality, powered by iZotope’s in-house MBIT+ algorithm.

RX Connect - DAW integration
Using RX Connect, which links your DAW and RX, cleaning audio with RX without leaving your DAW is quite a breeze. You just need highlight the parts of your audio, select Connect from the Audio Suite menu and send the region to RX as a “round trip”, which means I’ll treat the audio with RX then send it back to Pro Tools. RX will open up, apply the desired processing, click the “send back” button and commit the changes with RX Connect. It hardly takes a few extra clicks than using the standalone app and I’d say it’s very much worth it. To test the RX-DAW integration I took a 2-track live recording of a music performance with vocals and acoustic guitar, which had over an hour of material to be edited. The performance was very good, but plagued with technical issues so I had to remove hiss from the not-so-quiet noise floor, clicks/crackles from bad connector on the guitar, attenuate clipping on the vocals track, rebalance the piezo mic from the acoustic guitar. In short, the material had to be repair and made viable for mixing and mastering, and so I went hundreds of times through the processes of “select audio - RX connect to send to RX app - work miracles on RX - send back function - render”. Over and over and over again until all clips were crystal-clear. Integration with Pro Tools with pretty flawless in that regard, and I’ve found myself working quite fast - RX’s stability was great in that regard. One thing that helped me to work easier was RX’s “monitor” plugin, which allowed me to monitor the changes through your mixing chain.
The Scores
Sound quality - 5/5: Arguably the best sounding set of tools in the audio repair segment, RX can do things that are borderline science-fiction and will challenge common beliefs of what is possible and what is not. All around RX offers the best quality processing you can get but some of the modules really stand out, like the remarkables De-click and De-clip and also the extremely competent De-noise. De-clip really saved recordings that I initially considered unviable for anything serious, it’s really something special and would do great on a simple plugin on it’s own - I think I’ve said the same thing a number of times to be honest..but a man can dream. De-reverb and Ambience match are also worth mentioning and they’re arguably the best tools on their categories, providing spectacular results. Overall the sound quality of the modules are amazing, they became industry standards for very good reasons and will be very hard to be topped.
Ease of use - 5/5: RX is mostly accessible and easy to use, I say “mostly” because some of the modules have a steeper learning curve than others. I’d say RX is “easy as it can be” and in that regard it is expected that removing the room fan with Spectral Repair poses a tougher challenge than removing simple clicks or lowering a high noise floor without killing your top end. On most occasions RX is in fact totally straightforward - the De-noise, EQ match and De-Reverb modules are surprisingly easy for what they can do and achieve. The standalone app is really a breeze to use, with clean and uncluttered interfaces not only for the main editor but also for all the modules Using RX inside a DAW with the Connect plugin is a bit more laborious since you have to set up the Monitor plugin and RX’s output accordingly, but it’s nothing complicated. There’s also the possibility to use the provided plugins for most of RX modules as regular plugins in your DAW and that works well on some occasions but since the Connect/Monitor setup was so easy I ended up rarely using them. I should also say that the documentation is nothing but stellar, with a big HTML help file that covers everything in great detail, with a very clear language that really helps to get the best out of each module and of RX as a whole. If that wasn’t enough, iZotope recently released a website with a ton of tricks called the “RX cookbook”, with a good search mechanism that allows users to sort articles according to each RX version, module or real-world application - definitely very helpful resource that adds further points to RX’s ease of use.
Features - 5/5: Both standard and advanced versions are spectacular in terms of how much they pack. Needles to say that the advanced version provides greater depth and audio processing options that makes the “advanced” label a very deserved and rightful one, but standard version is also very well featured and will cover most common scenarios. Nevertheless, in true Gearslut fashion, I’d totally welcome less offline processing and more real-time action. I can understand the reasons behind “not having so much online processing” but it’s not a distant reality as computers are always getting more powerful and in that regard I’d like to see better online processing with lower latencies in the future.
Bang for buck - 5/5: Once you start using it, RX quickly reveals itself as an immensely valuable set of tools and it’s hard to imagine life without it. However, the gap between standard and advanced version still feels like it’s a bit too wide despite iZotope’s efforts to narrow it. Nonetheless, RX Standard offers an unbelievable bang for your buck and I would give it a six out of five stars if such score was possible. On the other hand, I feel like the bucks required for the advanced version are a bit too much and I’d welcome some further licensing options for single modules, two/three modules combos and anything that lessens the burden our pockets. Pricing debates aside and regardless of which version you end up choosing, RX is an investment that quickly proves to be very worth making and RX really inspires a lot of confidence.
The verdict: iZotope’s RX 5 arrives on its fifth iteration with as an extremely well rounded and matured solution to rescue your recordings most problematic moments and to save yourself a world of troubles that you’d end up without it. RX is the closest thing to insurance when it comes to audio recordings and it feels like having a safety net when you have no options other than face the situation and roll with that problematic recording. That might sound a bit dramatic but it’s definitely the case when you starting using it and the miracles start to line up in front of you. What RX can do can not be described in other terms. It’s really a decisive tool that can make a huge difference, both when turning bad recordings into something that can actually be used and when some polish is needed on less than stellar recordings. Once you realize its power, RX becomes almost as necessary and indispensable as your DAW.
Recommended for absolutely all professionals or studios dealing with any aspect of audio, be it on post-production for other medias or on mixing and mastering music. RX is also an indispensable tool for professionals doing forensic, restoration and archiving works.

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Post-script: As I was on the closing stages of writing down this review, iZotope recently launched Dialog De-Noise, De-clip, De-click and De-hum as 4-plugin package called “RX Plugin Pack” that furthers the options for new users. As I’ve mentioned above I believe some of those would make fine products on their own, especially Dialog De-Noise and the incredible De-clip, and this package is a very welcome addition to their audio repair tools and a good entry ticket to RX’s universe. At $129 (MSRP) the pack definitely has some great value but I missed an upgrade path to RX Standard at a friendly price. As their past actions have show, iZotope certainly is not afraid of changing their pricing and distribution strategies so it will not come as a surprise if we see that happening at some point. Nevertheless, I really have to applaud the effort they’re making to make these tools available to a wider range of people and their respective budget limitations.

Best De- Click Settings High Frequencies Izotope Rx 3


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