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Three Compliance Metering Plug-ins

Versatile Old/New-Style Preamp With EQ

Several years back, the International Telecommunication Union (ITU), composed of engineers from around the globe, issued recommendation ITU-R BS.1770, which described a new style of loudness metering that would measure long-term average loudness in a clear, simple and easily repeatable way. The European Broadcasting Union used this metering method in the creation of its new broadcasting standard outlined in a document titled: R.128. On December 13, 2011, the Commercial Advertising Loudness Mitigation (C.A.L.M.) Act was signed into law in the United States. This law mandated the FCC to recognize and enforce the ATSC’s interpretation of ITU-R BS.1770, which is a standard titled A/85.

The standard calls for a style of loudness metering that measures long-term average loudness in a clear, simple and easily repeatable way. All programs must adhere to the network standard within +/- 2 dB. To that end, access to compliant metering is certainly useful during recording and mixing, and essential during mastering. In the U.S., the standard (A/85) is based on -24 dBLKFS (long-term, k-weighted, full-scale) while the E.B.U. standard (R.128) uses -23 LUFS (loudness units, full-scale).

TC Electronic LM6 Native Plug-in

TC Electronic LM6 Native Plug-in

One of the first meters designed in accordance with ITU-R BS.1770 was the TC Electronic LM6 meter for use with its System 6000 multichannel digital processing platform. Due to demand from non-6000 users, TC Electronic issued the LM5 TDM plug-in for use with Pro Tools HD only. It was a sleek, screen-space-conscious interpretation of the original LM6, in plug-in form. Now, TC offers the LM6 Native plug-in, which will run as VST, Audio Units, AAX, RTAS and, with the Version 1.2 update, AudioSuite. Interestingly, this new plug-in seems to have been ported over from the 6000 version, instead of being based on the LM5. This being the case, it takes up a bit more screen space than the LM5. On top of that, controls that were originally manipulated by motorized faders on the 6000 Icon remote control are now being controlled by mouse drags, which is sometimes clunky and awkward. That aside, however, this tool has long been popular in its original form for a reason and is welcome in native DAWs.

The most dazzling feature of the LM6 is the large “radar” meter that performs a revolving wipe, showing average loudness over a long duration. It can be set to span as short as a minute or as long as a day. The decibel resolution can be adjusted to cater to the needs of the particular project. I like to set a finer resolution for spoken word that doesn’t vary too greatly in level, but displays a wider range for more dynamic content. Certainly, watching trends and deviations in this way rivals any other system yet devised for long-term loudness metering, especially when referencing the meter during tracking situations. Rather than looking back and forth between Pro Tools waveforms and the plug-in, the radar’s interpretation of the waveform paints a clear enough and meaningful picture on its own.

Wrapped around the radar is a momentary loudness meter, which is particularly useful as a starting point when level-setting and for responding to sudden changes. The user-selected nominal volume is displayed at 12 o’clock on the dial, with the aim being a signal that dances around that mark. Below the radar, to the right and left are two user-selected descriptors. Each can be assigned to one of the following choices: Program Loudness, Sliding Loudness, Loudness Range, Maximum Loudness. These values are listed out to one decimal value, and are displayed cleanly and simply for an easy glance. There are also individual momentary peak meters for each channel of a multichannel mix. These meters display dBTP or “True Peaks.” While these vertical bar-graph meters would be displayed in a separate page of the LM5, they are off to the right side of the radar, as they appeared in the 6000 LM6. This, plus the wide vertically oriented page selection buttons along the left side, make the plug-in unnecessarily wide relative to the LM5’s small page buttons along the plug-in’s bottom.

In addition to the radar page, there is a “stats” page, which displays all pertinent statistics in a clear, concise list. Two additional pages of settings include a variety of available presets that will change the descriptors displayed, nominal level and metering ballistics. Presets include ATSC A/85 compatibility, EBU R.128, the Japanese TR-B32 standards, and presets for CD and cinema mastering based simply on ITU-R BS.1770-3 (the third and most current revision of the ITU recommendation). Besides displaying information in the plug-in itself, a log file is automatically generated upon opening. The LM6 will log the time the plug-in was launched, the duration of audio run through the meter, the peak and average loudness, and when the plug-in was closed. Other compliance meters offer a much greater level of detail in their log files, but certainly this log, if sent along with an audio file, would be sufficient for dialnorm encoding or compliance confirmation. And with that in mind, the included AudioSuite version allows for faster-than-real-time level-checks and logging of premixed files.

The LM6’s CPU usage was minimal, and an instance of the plug-in contributed zero samples of delay. After upgrading to Version 1.2, I experienced an easily remedied quirk worth noting. The automatically created log file will be saved in a destination of your choosing. The default destination after the update, however, was a non-existent folder. Until I either changed the destination or actually created the folder that it was looking for, the plug-in would produce a CPU overload error and pause playback. The only other thing that I found disappointing was the DAW synchronization. The plug-in automatically pauses in sync with the Pro Tools transport and will resume reading when playback is initialized, which is great. But it would be nice if there were an option to automatically reset the meter upon stopping playback and returning to the top. Instead, the radar pauses during a stoppage, but then just picks up where it left off. That said, the LM6 is certainly user friendly and a worthy contender for those looking for an able meter with a broad range of capability.

TC Electronic

Product: LM6 Loudness Meter

Price: $599 direct

Pros: Great-looking visuals.

Cons: Not as streamlined as the LM5. Minimal logging.

Waves WLM

Waves WLM

The Waves Loudness Meter is one of the latecomers to the game of loudness metering, and because of that it seems that Waves was able to sit back and learn from the successes and failures of its predecessors. The WLM complies with ITU-R BS.1770, A/85, R.128, and even the TASA leq(M) standard for cinema trailers, which considers frequency-dependent audience “annoyance” levels. The loudness measurement throughout the WLM can be toggled between reading the whole program average, or it can automatically detect when dialog is present and only measure then. It can also measure using the EBU-style gating function that meters only when audio breaks a certain threshold.

The best thing about this meter, though, is its clarity and simplicity. Three large boxes across the top show short-term loudness, long-term loudness and loudness range. Giant numbers are displayed with no decimals, and then smaller versions with a single decimal are displayed dimly, and below. When loudness hits the target value, a graphic target with a checkmark appears. This couldn’t be clearer or easier to read. Just below these value boxes are a pair of horizontal bar-graph meters displaying momentary level and true peak level. Each meter has a peak reading displayed to the right of it. These bar graphs are color-coded to indicate when audio is in the optimal range, when it goes over and when it falls below. Counters indicating the number of overs and unders reside just above these meters. They used a clever trick to log the time of these occurrences without even having to check the log file. The WLM plug-in can write a layer of automation that stays at 50 percent when the audio is in the optimal range, but jumps to 100 percent when an over occurs, and 0 percent when an under occurs. It imparts no sound, but merely allows a quick visual reference.

Below the metering is a box containing all of the user-configurable options. Here, the buttons to toggle between whole program (LM1) or just dialog portions of the program are available. The meter’s weighting is manually selectable between ITU-R BS.1770-2, leq(A), leq(B), leq(C) and leq(M). The target loudness can be adjusted, and not only will this change when the target symbol registers in the long-term loudness box, but it will slide a green arrow marker along the momentary loudness meter. The resolution and units of the momentary meter can also be user-adjusted, and will change relative to the weighting curve, as well. Changing the short-term minimum and maximum values will slide where the color-coded over and under areas on the momentary meter exist, and will also change the point at which overs and unders will register. Adjusting the “True Peak Max” will display a red zone on the True Peak meter, displaying overs on that scale.

Other settings include a drop-down menu that gives the ability to change between metering all the channels, any individual channel, or just the L, C, and R, or L and R. Also, a manual equalization curve can be used before the selected weighting curve. I would love it if this settings box could collapse into the plug-in and be shown only when needed. Not only does it eat up a good chunk of screen space, but it is also somewhat distracting from the otherwise streamlined look.

The logging on the WLM is very thorough. Either a real-time log can be initialized, where generation will begin from then on, or an offline log can be generated, which is useful when working with the AudioSuite version. I was able to open the log file with Numbers without any hassles. There were 13 columns of information showing times, average levels, peak levels, warnings and other pertinent information. A new row is generated every second, at which time all of these values are calculated. With the log file open while the meter was running, however, the file didn’t update in real time. I had to close the file, and open it back up to see the latest information. This wasn’t surprising, as I don’t see how the plug-in could “talk” to the spreadsheet software, but it’s something that should be noted.

Altogether, this plug-in is slick-looking, easy to read and gets the job done. Logging operation is smooth, without ever hiccuping, and CPU usage is minimal, and it contributes no delay when being used. Syncing to the Pro Tools transport provides a similar experience to the LM6, where reading will pause and play along with Pro Tools, but resetting is strictly manual. The WLM will support measurement of mono, stereo or 5.1 audio.


Product: WLM Loudness Meter

Price: $240

Pros: Clear, simple reference. Great logging.

Cons: Not as much visual information provided as LM6.



The NuGen ISL is designed to address another fundamental component of A/85 and R.128 compliance. For years, we have relied on peak limiters where a threshold is set at a certain decibel value, and the limiter is engaged if the value of a digital word, or “sample,” exceeds that threshold. The recent realization is that sample-accurate peak measurement doesn’t always tell the whole story. When D/A converters reconstruct the string of samples and turn them back into voltage, oversampling may occur, which essentially creates smooth curves between one sample and the next. In some cases, these newly created curves exceed the limiter threshold and will clip later down the line. In other cases these inter-sample peaks will clip during AAC, MP3 or AC-3 encoding. Traditional brick-wall limiters like the Waves L1 have no ability to predict this, and as a result, many engineers will just play it safe, lower the threshold and sacrifice headroom.

During the creation of the ITU-R BS.1770 loudness metering model, engineers also developed an algorithm to meter inter-sample peaks by oversampling within the metering software. When oversampled peaks are measured as opposed to sample-based peaks, the term True Peaks is applied, and quantified in dBTP. The A/85 spec demands that program material stays below -2 dBTP, while R.128 sets the ceiling at -1 dBTP. Measuring in terms of dBTP is also useful in the music world where mastering hot is a common practice, and hot masters can lead to clipped MP3s when limited with traditional limiters.

The NuGen ISL is a True Peak limiter, which means that it is a brick-wall limiter whose threshold is set in terms of dBTP rather than sample-based peaks. This makes it the perfect tool for broadcast and post-production, because you can set it and forget it and then rest assured that you will always stay compliant and never clip during encoding. Controls are very similar to what you would find on any brick-wall limiter, so it is easy to pick up. Large vertical bar-graph meters display input and output. A slider on the input meter sets the ceiling of the limiter (it can also be input numerically in a box found below this meter). The gain reduction is displayed on a set of meters in the middle of the plug-in. ISL can operate in mono, stereo or 5.1, and a Channel Link control, set in terms of percentage, determines whether the multiple channels will be limited individually, or how much bearing they will have on each other’s gain reduction.

In a deeper menu, there are settings to control the color scheme of the meters, which the user can break into four color bands. The decibel break points are user-selectable, and the color for each of those bands can be chosen from a large color palette. Momentary and maximum peak indicators can be engaged or disengaged selectively, and the meter decay ballistics can be chosen between instant, DIN or the Nordic ballistics. The meter’s routing is user-selectable between the Dolby/Film standard, the DTS standard, and the SMPTE order. Changing orders actually changes how information is routed into the plug-in, so, for example, channel 2 is always displayed on meter 2, but you can change whether that is labeled center or right.

A look-ahead setting allows the metering algorithm to respond to quicker transients and level them without error; however, reducing this setting can make the sound a little punchier. It is easy to compare the difference in settings using the “Listen Mode” controls. In “Difference” mode, you can listen exclusively to what information is being limited and make adjustments accordingly. A-B’ing this function on and off was very revealing when judging the look-ahead setting and the release control, which adjusts the time that it takes the limiter to return to a state of zero gain reduction.

Naturally, the original goal of the plug-in was to set a ceiling, have it tame the mix’s peaks, and not make it work too hard. When it was only reducing a few dB, it was essentially inaudible, as planned. What was really impressive, though, was that I could dig deep, reducing gain significantly, and still the plug-in stayed incredibly clean. Just to see how far I could go before I heard negative effects, I would play with throttling the input gain and scaling back the output ceiling, and even with 30 dB of gain reduction, quick-transient sounds like machine guns still maintained a clean, usable sound. Pushing beyond that, things started to sound distorted, but the sound was much more like analog distortion than I was used to hearing from a plug-in.

With the ISL’s ability to prevent True Peak overloads, and the only rival product being Flux’s Elixer, it’s hard to imagine the ISL won’t catch the attention of many broadcast engineers. The sound, however, is what I found the most striking. I would be inclined to use it over the Waves L1 in post-production situations for the True Peak limiting, but even in music mixing or mastering for its ability to get loud very cleanly. Performance was smooth without ever glitching, CPU usage was reasonably efficient, and in a 24-bit, 48kHz Pro Tools session, it only imparted 64 samples of delay on the master fader.

Brandon T. Hickey is a freelance engineer and audio educator.

NuGen Audio

Product: ISL

Website:nugenaudio.comPrice: $249 direct

Pros: Easy to use. Sounds fantastic.

Cons: 5.1 max, no 7.1 or higher yet.