For many years, the restoration software hierarchy was etched in stone. The top tier featured outstanding performance at a premium price (often costing thousands of dollars per application). Outside of restoration houses and high-end mastering facilities, most engineers had to make due with more affordable solutions. Unfortunately, affordable titles often worked poorly, caused artifacts, or left the audio worse off than it started. But that landscape has been changing. Algorithmix now goes toe-to-toe with CEDAR for the world-class title while many other vendors have entered the market, creating a truly pro-level middle ground. The RX line from Cambridge, MA-based iZotope offers great sound quality at prices targeted for different budgets.

RX comes in standard and advanced versions. I tested the RX Advanced suite, which includes extended options for user- tweaking as well as iZotope MBIT+ dithering and iZotope 64- bit SRC resampling. (For a full comparison, check out the website.) RX runs standalone or within your DAW, and goodness bless iZotope, it's cross-platform. We were able to run it in Mac OS X on a new Mac Pro and in Win XP on a Dell with no problems.

RX comes with a set of five tools: Hum Removal for removing line noise and electrical hum; Declipper for softening clipped audio; Declicker for addressing crackle, pop, and digital impulse fragments; Denoiser for getting rid of noise; Spectral Repair, which is almost like Adobe Photoshop for audio. There is also an Advanced Spectrogram to help inspect audio visually.

I was pleasantly surprised the first time I ran RX. The workflow, interface, stability, and configurability suggested a title in its fourth or fifth version release. But as of this writing, it's only at 1.05! I was able to get usable results without as much as a glance at the manual. At first, I found it hard to navigate quickly. I bounce around among multiple DAWs, and I simply can't remember every vendor's keyboard shortcuts. On a whim, I investigated the prospects of customizing commands to match the zoom and select commands in Sequoia. (At one time there were few applications that offered any key customization.) No problem for RX. Before I knew it, I was moving around like I had been using it for years.

Speaking of interfaces, I love/hate both Mac and Windows machines, but you can generally count on Windows programs to look like some nimrod designed the GUI. But RX (and sibling Ozone, for that matter) is the epitome of sleek design. It's a cross between futuristic starship and Formula One racing. Controls are delineated, and the colors are not straining over long hours. Soothing to look at makes for better days at the office. Okay-it had to be said.

Declipper, Declicker, and Hum Removal were all very effective; although you'll get the best results from Declicker by adjusting the settings by hand. For the review, I spent most of my time with Denoiser and Spectral Repair. These were the standout tools in RX.

Removing noise from a signal is actually easy. But removing noise without hurting the underlying audio is difficult. There are many ways to go about this process, but according to iZotope, RX has some advances over its competition. For example, the artifact-reduction process draws from techniques adapted form digital imaging. The company claims that this approach reduces artifacts (chirping, tweeter angels, and phase smearing), leading to more natural sounding results. From my tests, I think they are on to something. Another feature is multi-resolution processing (instead of conventional broadband noise reduction). This approach selects the best time-frequency resolution for every portion of the source signal. At the expense of being more CPU intensive, this analysis provides RX with a better determination of what is noise (and hence should go) and what is desired signal (and should be left untouched).

Using live recordings of a symphony hall that suffers from variable HVAC noise and occasional street traffic, Denoiser produced good to very good results, depending on how high of a resolution I chose. It came down to subjective opinion; I have other tools that removed more noise, but they also introduced artifacts. In contrast, RX removed a percentage of the noise but did not harm the audio. On balance, I think it's better to do less harm than to throw out the proverbial baby with the bathwater. You can also preview

your work, or process it and change your mind via the undo history. And I must confess my love for RX's batch mode. I was able to set up Denoiser settings, queue the noisy tracks, and walk away. Since high-resolution processing takes time, this was a workflow lifesaver. Well played, iZotope.

The Spectral Repair module is the gem of this collection. For those new to this process, the audio is presented visually in a spectrogram. The x-axis is time, y-axis shows frequency, and the color intensity represents relative loudness. Bright colors are louder and dark colors are quieter. Forget the textbook definition-you can see what's going on in the audio. Clicks, coughs, and other gremlins poke out like me at an insurance convention. For more precision, RX allows you to overlay the wave display we are accustomed to and adjust its transparency. Once you find your glitch, you can do a number of things to repair it. My favorite is the attenuate function. This is killer on pops and plosives. With one keystroke you can reduce the offending signal to a more manageable level. To do this by hand would require numerous operations and may not sound as smooth as RX. You can also replace offensive audio with interpolated audio ("Computer, what would have happened had the noise never occurred?") or by patching with a section of audio you choose. Think of it as repair putty for audio dings and dents. Not impressed with plosive crushing? Okay campers, raise your hand if you have a drummer or guitar player who decides it's a good idea to talk, click sticks, or drop headphones before you're done recording a pass. With Spectral Repair, you can erase such hiccups and keep the nice long fade-out you wanted.

It has been difficult to limit the word count on this review. I could write about the numerous features buried in the software. But I have to go put my Waves Restoration Bundle on eBay. Every studio owner should consider the base- version RX, and mastering engineers should strongly consider Advanced. Fortunately, you can download a full demo from iZotope. (RX $349 MSRP, RX Advanced $1199; -GH 


Tape Op is a bi-monthly magazine devoted to the art of record making.

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