NuGen Audio Loudness Toolkit 2 Review – Stepping Into Surround

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This is the first article in our new series ‘Stepping into Surround’. Today, music is being presented more frequently in multichannel formats. For work in video game and broadcast, a knowledge of working in surround sound is a requirement, and the multichannel discipline has also been courted with by musicians over the past decade or so. I can see a lot more music work involving surround sound in the future, and we at AudioNewsRoom wanted to introduce a series that would take a peek at working in Surround; a taster, if you will, for those interested in dipping a toe into the world of multichannel audio.

To start with, we’re taking a look at an essential plugin bundle that you’ll need to look at if you intend to work with multichannel audio: Loudness Toolkit 2.

Nugen Audio is an established company based in the UK providing excellent software plugins for use within Audio, in all areas of the professional industry – Music Production, Post production and Broadcast. Their products are designed to make workflow easier, with better final results, for less operating cost. Nugen are held in esteem by professionals across the board (including the Audio Director of Austin City Limits – a favourite of mine!)

Mixing for Post and Broadcast is a technical discipline; quite different from mixing for stereo, and generally with very defined protocols and standards to meet. The Loudness Toolkit 2 is a recently upgraded collection of 3 software plugins that make the potentially complex process a massive amount smoother, and faster.

True peak is a relatively new algorithm that calculates the true peak amplitude of a signal, and defines the peak as a new measurement dBTP. Quite a lot of the meters in-built in DAWs are PPM meters, or Peak Program meter. PPM meters are fairly accurate, but the true peak algorithm allows for inter-sample values, which provides a more accurate reading. Not all level meters will allow True Peak monitoring – especially the ones in your DAW. If metering is important, I highly recommend getting a good 3rd party plugin to accurately read your levels. Here’s a great video by an amazing moustache with a lovely face, demonstrating the differences between PPM and True peak.

ISL2 is a True peak limiter used for mastering final tracks for broadcast and music release. It’s a plugin designed to be used on the master out, and will transparently limit your mix to whatever level you require, whether you’re mixing in mono, stereo, or surround.

The GUI is excellent, with ‘traffic light’ colour input levels on the left, a reduction level meter in the centre window, and output level on the right. All have infinite-time levels, so you can check the highest peak levels for the piece. If you need more information, you can change the reduction level view to show input and reduction in waveform.

I would put ISL2 as the final limiter on a master buss. You can increase the input gain, adjust the threshold (Brickwall), adjust look ahead and release of the incoming signal. All you need to get the levels you want. The threshold setting is where the brick wall stops, so to speak. No signal will pass this level. unlike traditional limiters, where the threshold determines where the limiting starts. This makes for a much simpler set up. Move the threshold to the limit you want to: -10db for example, and you can be confident that the signal will NEVER pass that level. This means that for those that used to worry about inter-sample peaks causing distortion, worry no more. Won’t happen.


The Auto-release function is interesting also. Upon initiation, the auto release will instantly release the compression, but extends the hold time of the limiter to after a full wavelength of any low frequency signal has passed. This creates a great balance between super short release time, without the distortion that occurs when low frequencies trigger limiting on an otherwise good signal level.

Not only is ISL2 useful for broadcast however. I found that as a limiter, it compared very well with limiters that are well established for mixing music. It’s extremely transparent, even driven hard. I found that it didn’t start to affect the sound noticeably until almost in the double digits.

I really loved the channel link function – you can choose a link amount between the two channels in stereo, or all the channels in multichannel. With less link percentage, your channels are processed more independently, which can lead to movement in the imaging of your mix (steering). If your channels are 100% linked, you can get ducking sounds on channels unnecessarily. With the choice of amount, you can find the perfect balance between them, to get a smoother compression between all channels. You can see in the middle window how much ducking and steering (image) you’re creating depending on the amount of linking you’ve chosen. In 5.1 there’s an excellent feature where you can completely unlink the centre channel (which tends to have the most gain reduction), but can link the remaining 5 channels fairly tightly, thus getting an even better compromise on your compression.

I also liked the different ways that you could listen to the effect the limiting has on the audio. There’s a DIFF button, that enables you to compare the original audio input, and the output results, to ensure the sound quality remains good.

The presets are really important in this plugin, as with all of NuGen’s plugins. The presets cover all the standard industry requests for deliverables, for international broadcast, DVD mastering, and also for Mastering requirements for various formats such as iTunes.

Here’s a video looking at the ISL2 true peak limiter:

VisLM 2
Although I am a huge advocate of not staring at levels, good metering is essential at some point in the process. VisLM 2 is a big step up from your DAW level meter. It delivers a combination of level readings, with both True Peak and Average loudness meters, useful for checking that your mix is at the correct level required for broadcast and any other requirement for post audio.


The big window in the GUI shows the loudness level of the audio across timespan – so you can see a very clear history of how loud the audio has been. Within the options you can set different loudness levels to different colors, so you can see at a glance whether the audio is staying within the dynamic range you want it to. You can sync the plugin to Timecode, enabling you to change the loudness levels of a section, link it to the plugin, and alter the average loudness results for the entire audio, without having to run through the whole piece again. For short pieces this might not matter much, but when working on long form, this could be an essential time-saving element of the Vis-LM plugin.

The section on the right hand side of the GUI gives many different ways of checking levels. The left hand meters show momentary and short term loudness, and true peak levels with peak alarms. They can be switched or combined at a press of a button. There is True Peak level monitoring also, with a peak level visual alarm. There are 3 smaller windows that you can glance at to check numerical values for short term, integrated (average) and range of loudness levels (dynamic range).

There are options to change the region settings that you wish to highlight in the loudness History window, set highs and lows etc. As with ISL 2, again the presets are very important here. They represent an international collection of all the standards you are likely to adhere to: EBU R128, ATSC A/85 and so on. VISLM 2 works on any channel setup from 1.0 all the way through to 7.1, as long as the DAW you’re hosting it in allows. Very flexible metering plugin.

VIS-LM2 is obviously geared for broadcast and post. However, I was pondering its usefulness in music production – and again I can see it being a very valuable tool. As the music industry’s views change on Loudness, dynamics are once again starting to come back into play, which is an amazing result for music and music production. Gone are the days of trying to SLAM your track to the ceiling where it gasps for breath, losing all signs of life. This metering plugin will not only show you True Peak errors, which most DAW’s can miss, but will also very clearly give you a visual impression of the shape of the track, and will give you a number on the dynamic range. I can’t think of another plugin that does this. As I mentioned before, I’m not a fan of visual mixing – but to pop this on your music, and see where your dynamic range is at, and your average loudness, and the shape of the track, all in one glance, could be extremely useful.

Here’s a video of VISLM 2 from the makers, NuGen audio.

What is LUFS?
The audio industry has gradually been shifting away from heavily compressed audio back to a larger dynamic range. LUFS/LKFS is a relatively new standard of measuring loudness, or average loudness levels, to fight against over-compressed sound, and audio with short duration massive peaks (to grab attention, usually in the advertising industry). Here’s an excellent article by TC electronics outlining the industry’s changing attitude towards loudness, and how it applies to us sound creators.
Another video on LUFS – another important standard to learn about!

LM-correct 2
LM correct is an essential utility to ensure that files that are already mixed can meet the requirements set, without having to re-mix the project. Designed to work mainly within the Protools domain, there is also a standalone software available. In a nutshell, you load the audio file, or source file, set the parameters you want to meet in the Target, and hit GO. LM – correct automates the process of changing levels to meet True Peak, Integrated loudness, and LRA (dynamic range) requirements. It does it offline, and super fast. It’s a very simple looking plugin:

You can load in stereo, 5.1 and 7.1 interleaved or split files, and LM -correct will deal with them appropriately.


There’s a new feature that will take into account the LRA – the loudness range or dynamic range of the mix. This is extremely useful if your mix is being adjusted for a different delivery medium – say if you created a mix for film, and needed to quickly adjust appropriate for mobile, or television content – LM correct will quickly adjust the sound to create a mix that works.

The only slight problem with LMcorrect is that due to the way the plugin processes the audio, it can’t be used as a VST or AudioUnit. Therefore it can only be used in ProTools or audio suite compatible software. This isn’t too much of an issue however, as it can be used standalone, and the predominance of Post Audio use Protools anyway. You’re never going to be using this plugin in real time, as it only deals with audio files.

I have to say I was very impressed with LM-correct. I think I would be nervous to use this too often, as I’m a little anal about having complete control over my mixes. But If you were on a time crunch, you had a lot of files, and the deliverables included a bunch of mixes for different formats, LM correct could be an absolute lifesaver.

Here’s a video intro to LM correct:

Loudness Toolkit 2 is aimed at the Post and Broadcast industries. For those people, these plugins are absolute essentials! They are extremely stable, accurate and reliable plugins. They definitely speed up the process of mixing audio for Broadcast, by ensuring that you can accurately set, and see the levels and ranges you have to fit within. Some video work that I had to do recently for the Smithsonian institute passed QC first time. Amazing. That was unquestionably down to the efficiency of the toolkit, which I found myself relying on more and more. However, if you find yourself (as I do more frequently) standing in the growing space between music and mix, from stereo to multichannel, and moving into surround sound work for your music, I can highly recommend these plugins as essential starters to move into the multichannel world. Especially the transparent ISL2 Limiter – it compared favourably and musically with my other go-to limiters, but it does the same job with 5.1 and 7.1! The VisLM 2 will also ensure that your peaks are being restrained, but also provides a very useful timeline of dynamics and levels across a piece. Extremely useful information that you just can’t get anywhere else.

If you already own the Loudness toolkit, the upgrade to version 2 is $399. You can find out more on the NuGen Audio’s website.

Loudness toolkit costs $949/£590. The plugins can be also bought separately.

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NuGen Audio Loudness Toolkit 2 Review – Stepping Into Surround

by Andy Dollerson time to read: 9 min