By Cory Choy 

iZotope has just released its iZotope RX 9 Advanced with improved Ambience Match, De-hum and more, and I’ve been given early access to put it through its paces.

Cory Choy in Silver Sound’s Studio A

Full disclosure: I have been using iZotope RX Advanced since Version 3, and I consider the RX suite to be a necessity in the field of sound engineering. Other than my DAW of choice, Reaper, iZotope RX Advanced has become the program I find myself using the most. In fact, much like “Googling” something means looking it up on the internet, for me, “iZotoping” something has come to mean making it sound better via audio restoration.

That said, I always give my honest opinions while reviewing software and have tried not to let my appreciation of the company and product line color this review of the latest update. 

I am always very excited when an updated version of iZotope RX Advanced is released. iZotope’s suite of spectral editing, loudness and restoration tools is relatively affordable (with pared-down options at very good prices), easy to use, does not require a dreaded iLok (which seems to be constantly breaking and making my life worse) and works alongside most DAWs.

The big question when new tools are introduced is always what’s new and do the new features necessitate an upgrade. The last must-have upgrade, in my opinion, was iZotope RX 7 Advanced, with its introduction of Dialogue De-reverb, a tool that never ceases to amaze me.

What you’ll see when opening up the program

Let’s dig a bit into this latest version. What’s new in iZotope 9 RX Advanced? Thankfully, the UI is basically the same. This is nice because I don’t want to spend time learning how to use a tool all over again and re-find all the features I already know and love.

Upgraded De-Hum
RX 9 Advanced sports a new “dynamic” De-hum that allows for many more bands — with Dynamic mode, you can learn and remove any amount of hum with up to 1,024 dynamically variable notch filters (this means the bands change the amount of reduction adaptively).

When I saw this update, I knew exactly the piece of audio I was going to test: an e-learning project I had been tasked with restoring that had been recorded with a nasty buzz across many, many frequencies. In the past, De-hum was only good for removing a few bands, and it seemed much more suited for things in the low end. That has now changed in Version 9.

Notice the lines running horizontally across the audio — these lines make up the buzz and are what I want to eliminate while still preserving the voice.

After using the “learn” AI-based function and setting things as aggressively as I could, I saw a significant reduction across the most egregious low end and a modest reduction in the low end. So, I “learned” again and applied again. This then affected the midrange. I then “learned” a third and final time, and it did affect the high end, but I still heard a bit of the buzz while the speaker was talking.

In this picture you’ll notice the very high-end camera whine around 20kHz was pretty much unaffected. I needed to remove that manually. The three tries got me 75 percent there, and then I did the rest by hand. So if you are patient, this will give you a nice head start.

Modest improvement

De-hum is generally used on audio where the unwanted hum is a constant frequency. In this case, there were many constant frequencies I wanted to eliminate. While RX 9’s new De-hum definitely performed better than RX 8’s, it wasn’t a game changer on this very challenging project. But, I look forward to trying it on other kinds of buzz down the road. 

New Dialogue Isolate Algorithm and Module
iZotope’s Dialogue Isolate often feels like magic, and it works fast! And while I don’t think it was intended — and wonder if it was somehow the origin of the Dialogue De-reverb module — Dialogue Isolate can also remove some of the longer reverb on a voice and make it feel more present.

Dialogue Isolate made short work of that buzz.

One thing to be aware of with Dialogue Isolate is that it can sometimes act like a sledgehammer and, if used too aggressively, can make the voice feel artificial/stilted/robotic/glitchy — so be careful. To test this function, I decided to try the new-and-improved Dialogue Isolate on the same clip from the e-learning project I mentioned earlier, and wow! It worked amazingly!

Much better, in fact, than the De-hum on that same clip. How about that? More than one way to slice a loaf of bread, as they say. Wait, do they say that? Well, you know what I mean!

I also like that the new quality modes are the intuitive “good” and “best” rather than RX 8’s semi-esoteric “channel independent,” “joint channel” and “advanced joint channel.” One thing that I did notice, however, is that the new Dialogue Isolate on “best” mode did end up taking longer to process than the old one, but it’s still definitely worth it.

Notice the volume getting quieter and quieter as time moves on.

I decided to try it next on something a little gnarlier, and this audio had a pretty interesting problem. For whatever reason, the voices started out nice and loud, and present, but as time wore on, the volume got quieter and quieter, and the voices began to feel more distant. The goal is to make the entire file sound as even as possible, so what I ended up doing was raising the volume to fight against the decline. But that introduced hiss (in the digital realm, you raise both signal and noise at the same rate). My hope was to then use Dialogue Isolate to quickly rid myself of the noise.

What some of the audio, after being boosted, looked like — and then again after Dialogue Isolate.

It did a very good job of reducing the hiss, but the voice didn’t come out unscathed. I tried various settings, and then compared the sound to iZotope RX 8 Dialogue Isolate. I would say there was probably a 15-20% improvement in the new one. Not bad at all. Game changing? No. A combination of other modules and methods still ultimately sound better — even if they take a little longer. Still, in a profession where every second counts, 15%-20% improvement is definitely worth something.

Ambience Match: Complex Mode
Ambience Match is one of those game-changing RX Advanced features that have completely rocked my world. It has quickly gotten me out from between a rock and a hard place more times than I can count. Where it can sometimes falter a little is in a more dynamic background, particularly documentary sound with birds and insects, and footsteps.

I tried an ambience from a documentary I worked on in the past — Boblo Boats: A Detroit Ferry Tale — in “complex mode.” Looked cool, for sure! But when I took a listen, it retained too many “bad” sounds for me to use well. However, when I used a complex ambience that didn’t have elements I didn’t want in it, “complex mode” actually worked quite nicely! Good for times when you need to get some more mileage out of that 30-second ambience that already sounds great. However, if you’ve already got access to a robust sound library with longer ambiences, this is usually not too much of a problem. All in all, this is a modest improvement.

Here is the original and then the “ambience matched” version.

Final Thoughts
RX 9 is definitely an incremental improvement over RX 8, which was an incremental improvement over RX 7. For me, RX 7 was a must-buy and still a very strong and helpful tool, especially if you don’t have the money to upgrade now.

However, if you’re like me and every second you save is precious and you’re using RX constantly and professionally, then I would say the improvement in Dialogue Isolate alone is worth the upgrade.

Cory Choy is an Emmy Award-winning sound mixer, director,  producer and owner of Silver Sound in NYC