Audio, Reviews

NUGEN Audio Post-production Pack Review

NUGEN Audio Post Pack interface

Mixing and mastering audio for film, video or broadcast differs a bit from mastering for music. The media to master for will be different, as will the requirements of the industry. A UK developer, NUGEN Audio, creates professional audio tools for high-end music producers, post-production engineers and broadcasters. Among its partners we find Avid and Quantel. NUGEN Audio offers post-production mixing and mastering with a Post Pack that holds eight modules of which some can be used as stand-alone applications.

NUGEN Audio Post Pack interface

The NUGEN Audio Post Pack is concentrated around three major mastering tasks:

  • Ensuring the sound is loud enough while complying with loudness standards
  • Ensuring the stereo or surround soundscape is optimised across all frequencies
  • Adjusting the audible frequencies with minimal phase artefacts.

The NUGEN Audio Post Pack includes:

  • ISL, an inter-sample true peak limiter that works with mono to 7.1 files,
  • LM-Correct, a loudness measurement and correction tool that is available as a plug-in for AVID systems as well as a stand-alone application,
  • VisLM-H, a standardised loudness metering solution,
  • Visualiser, a user-definable real-time audio analysis tool,
  • Monofilter, a plug-in that allows you to control stereo width and phase correlation in low frequencies,
  • Stereoizer, a plug-in that allows you to control a variable stereo spread in mono and stereo signals,
  • Stereoplacer, a plug-in that realigns, corrects and redistributes stereo balance by frequency,
  • SEQ-S, the Linear Phase Spline/Match equaliser which we reviewed earlier.

When mastering for post-production, you don’t need to use every module. A few of them offer some overlap with others. For example, Stereoizer, Monofilter and Stereoplacer all three govern the stereo soundscape you’re trying to create. However, you’ll want to use Monofilter exclusively to optimise stereo width and phase correlation in the low frequencies of the audio spectrum, while both Stereoizer and Stereoplacer can be used on the entire audio spectrum of a file.

Another note I would like to make is: don’t expect any of these modules to make your mix sound deafening. When I published my review on iZotope’s Ozone 6, one reader’s comment was the app wasn’t any good because he couldn’t make his mix sound loud enough. I replied to the gentleman he should manage the sound levels per individual track, not trying to make the entire mix sound equally loud. One of the reasons is that “loud” usually goes hand in hand with a loss of dynamic range — the difference between silent and loud.

NUGEN Audio Post Pack Visualizer

The NUGEN Audio Post Pack isn’t aimed at making everything sound louder. It’s aimed at improving dynamic range with the SEQ-S equaliser, creating a transparent stereo soundscape and complying with loudness standards. To that effect, you’ll probably routinely use two-thirds of the provided modules in differing constellations.

Another remark: There’s only one module that won’t work with any DAW, sound editor or NLE except an AVID system: the LM-Correct module. This module is available to non-AVID users as a stand-alone app that will then work as a file based program. This means non-AVID users will first need to measure loudness levels with another module, e.g. VisLM, and then export or bounce the track or mix to a file, run it through LM-Correct with the measurements in mind and reimport if needed.

Loudness control

LM-Correct includes presets which can be automatically dialled in. Included presets are EBU R128, ATSC A-85, ITU-R B.S. 1770-02, etc. LM-Correct corrects for short-term loudness and for integrated or infinite program loudness. Especially for non-AVID users, LM-Correct is quite efficient as a back-stop processor which can ensure you end up with a finished file that is within specification. The interface is extremely simple with a minimum of preferences to be set. It’s probably the least sexy of all the included modules.

A lot more action goes on when you use ISL, the Inter-Sample True-Peak Limiter which is a plug-in to most DAWs or sound editors. It enables you to control peak levels in signals ranging from mono to 7.1 surround sound and offers a true brick-wall solution. It uses the standardised True-Peak algorithms of ITU-R B.S. 1170 and related standards and is suitable for the control of post production and broadcast. It can also be used to ensure downstream codecs not to introduce distortions into the signal.

NUGEN Audio Post Pack ISL

I tried ISL for the latter purpose. Although you obviously need to be familiar with audio controls in general, it’s very simple to operate. All you need to do is select a standard and set one of the two listen modes to hear the results. In Auto mode, you can accurately compare before and after while in Difference mode, you hear the actual gain reduction applied. Neither mode should be turned on during mixdown. If you want to assess and reduce your gain settings for Apple Mastered for iTunes, you’ll use the “afclip” algorithm. I used the default ITU setting to start from, but reduced gain a bit more by dragging down the white triangular reduction handles.

ISL’s Reduction Meters will show you if channels are linked or not. While you obviously cannot control loudness on each channel independently, you can control how independently each channel’s limiter behaves. If you know one channel will sound louder than the other a lower value will give the limiters more leeway in ‘deciding’ how much gain must be reduced to get a balanced result.

Regardless of whether you’re using LM-Correct or ISL, you’ll need to check loudness before you can start reducing it. NUGEN Audio VisLM-H is included with the Post Pack for that purpose. VisLM-H is a loudness metering system that complies with any of the existing region specific loudness metering standards. The “H” stands for ‘History’ and refers to a graphical representation of loudness values over time (up to 24h). This history can also be exported into a CSV file for analysis.

NUGEN Audio Post Pack VisLM

VisLM-H is available in 2.0 and 5.1 formats to ensure compliance with any plug-in host. The 5.1 version will work correctly with track counts from 1.0 up to 5.1 in hosts that support it. Just as ISL is a True-Peak limiter, VisLM-H is a True-Peak as well as a loudness meter. In EBU mode, the meter offers the ability to have one of a range of gates active. VisLM-H also offers the ability to measure Loudness Range or the variation of loudness measurement of a section of audio. LRA can help determine whether dynamic treatment of the audio is required.

I tested the VisLM-H stand-alone version with an Apogee Duet iPad/Mac and an sE Electronics se2200A microphone. The stand-alone application is designed to monitor ASIO Audio Inputs, turning it into a free-standing, sophisticated and standards-compliant input loudness/volume meter. Whilst the VisLM-H plug-in doesn’t need calibration when it’s used inside a DAW, it can be useful to check and set the stand-alone version to ensure there’s no attenuation or filtering going on. The VisLM-H stand-alone metering system can therefore be calibrated quite simply with NUGEN Audio offering guidelines in their user guide. The meter proved to be very sensitive and operating with no lag whatsoever.

I also tested the accuracy of the VisLM-H system versus Sony’s loudness implementation in Sound Forge Pro Mac 2.5.0. This test doesn’t tell the true accuracy of the VisLM-H meter as I don’t know how accurate the Sony’s meters are, but it did tell me this: the two metering solutions gave identical results, with the Sony system very slightly lagging behind (!) the VisLM-H system.

Stereo and soundscaping

Visualizer is a comprehensive metering and analysis tool. It can be used as a plug-in and a stand-alone solution. Contrary to other such tools, Visualizer contains every analysis scope or graph you can think of, including vectorscope, stereo spectrogram and spectrum analyser, correlation by frequency and more.

The whole system is crammed into a unified interface that — unlike most other NUGEN Audio windows — can be scaled to accommodate for every waterfall or scope panel. It’s almost redundant to mention: you can customise every aspect of the analysis meters, graphs and scopes, including ballistics, colours, peak controls, splits, margins, etc.

Monofilter is a stereo width and phase correlation plug-in control for low frequencies exclusively. Its interface isn’t anything like what I’ve seen so far in that looks like a funnel that you can increase or decrease in size. The controls allow you to set lowest and highest frequencies areas. The narrower you make the lowest frequencies area, the more centred these frequencies will sound and vice versa. The slope between the narrow and large area can be made quite vertical — abruptly changing stereo width — or gradual.

NUGEN Audio Post Pack Monofilter

In addition, this plug-in offers phase correlation control and analysis on input with the ability to shift phase and adjust phase correlation of left and right output, alongside an analysis. As with other modules, the excellent user guide contains a part dedicated to practical applications of this tool. However, in this case and perhaps with the exception of phase shift, I think the tool is self-explanatory.

Stereoizer is more or less a traditional control plug-in for spreading stereo into mono and stereo signals. At the very least, it has the traditional half-circle interface, although its controls offer more than the average stereo spread plug-in. Stereoizer is especially suited for creating stereo images that are also mono-compatible. It’s unique in that it has controls for inter-aural intensity difference (IID) and inter-aural time difference (IIT) settings. You can also set linear width. A dynamics section introduces movement into the stereo spectrum. The controls modulate the IIT and IID algorithms.

NUGEN Audio Post Pack Stereoizer

Whereas Stereoizer is somewhat like a traditional stereo spread plug-in, Stereoplacer is another quite unique plug-in for stereo realignment, correction and redistribution. This plug-in offers a window that looks like an EQ window with frequencies along the X-axis, but with the decibel values along the y-axis representing values to the left respectively right channel. In this window, you can create as many control points as needed. Dragging a control point to the top makes those frequencies come from the left more and vice versa.

As with an EQ, control points have a “Q” factor. The effect can thus be made sharp, i.e. manage a very narrow band, or smooth with the effect building up over multiple bands. Of course, the incoming signal can be analysed with the plug-in, as well as the output signal be shown.

NUGEN Audio Post Pack Stereoplacer

Finally, the Post Pack includes the SEQ-S linear phase spline and match EQ, which is capable of up to 7.1 sound, stereo mid-side operation and automated spectrum analysis. I reviewed the SEQ-S equaliser plug-in in 2014.

As with many of NUGEN Audio plug-ins SEQ-S isn’t your average EQ. It’s a linear phase EQ, which means the phase shift is linear across the frequency spectrum. Traditional EQ algorithms use a mathematical technique known as Infinite Impulse Response (IIR). This provides low CPU usage but there is an important side effect known as Phase Warping. This is the distortion of the relationship between frequency and phase.

The computational algorithm used in SEQ-S is based upon the Fast Fourier Transform (FFT), a much more involved process. FFT transforms the audio data in the frequency domain before applying frequency related computations and then transforming back into the temporal domain. The advantage is that the frequency and temporal relationship remains intact, which is what we call linear phase transformation.

NUGEN Audio Post Pack SEQ-S

The audible result is that any adjustment creates a clearer sound, a much more transparent EQ. While Phase Warping also affects clarity of transients (Phase Smearing), linear phase calculations do not suffer from this, producing a sharper audio image.

In every day use, SEQ-S has the distinct advantage of being extremely simple to use, with for example the ability to draw the EQ curve directly with a mouse or pen/tablet. SEQ-S also doesn’t force you to use zones but when you opt to use them anyway, you can create them as needed. SEQ-S offers three EQ envelopes, with each envelope assignable to a single or a combination of input channels.

Again, this plug-in can be customised pretty much the way you want, with a choice of banding options that include psycho-acoustic scales like Bark and Mel, different resolution settings with a maximum FFT size of 16384 that’s useful for mastering especially. SEQ-S performs its internal calculations with 64-bit floating point accuracy, but most DAWs will truncate the output to a lower bit-depth. Several options are offered to handle this with or without dither.

Finally, SEQ-S is a Match EQ, which allows you to match the EQ spectrum of a source section of audio with a target piece.

The results you can achieve with SEQ-S by itself are impressive, especially considering the small effort it takes to get there. I did have one minor problem with the SEQ-S working window: you can zoom the spectrum in and out by dragging in the margins of the display. I found it too easy to drag there by mistake, but this sort of operator’s error obviously doesn’t affect the audible results you can achieve any bit.


There exist excellent mastering plug-ins on the market that combine all mastering features into one interface. That might look like it’s more efficient, but my experiences with NUGEN Audio approach don’t confirm that it is. In fact, there’s no disadvantage of having separate modules that make up one mastering system, quite on the contrary. The NUGEN Audio Post Pack presents its user with several tools from which an expert will quickly be able to pick the right ones for different needs.

While previous experience with SEQ-S had already convinced me of the high quality of NUGEN Audio’s technology, the Post Pack only strengthens that opinion. I can understand why many broadcast companies use NUGEN Audio to comply with worldwide loudness standards and why music producers swear by the stereo plug-ins to create mono-compatible stereo files that allow listeners to close their eyes and “see” every instrument in space by simply listening to the music on a good pair of speakers.

NUGEN Audio is used by music producers and broadcast companies from Japan to the US. The Post Pack costs €890.00 ex VAT.