Another angle that broadcast music mixers may be more used to is the concept of loudness and loudness metering . It ’ s a big topic that needs exploration before we look at how it can improve your drive-in or livestream mix .
Typically , most mixers are accustomed to using the standard meters available on their console . Whether they are the PPM LEDsegment meter on your digital desk or analog VU , we use these meters to gauge what our audio is doing . In broadcast , due to regulations to ensure commercials are no louder than the programs they accompany , music mixers routinely use loudness metering , which is a completely different animal than the standard PPM or VU meters used during a standard FOH gig .
But wait , aren ’ t volume and loudness the same thing ? What different information does a loudness meter provide that a PPM or VU doesn ’ t ? The answer lies in the original design function of the PPM / VU meter . A VU meter is designed to measure an electrical level . 0VU is generally accepted to measure the signal of + 4dBu ( line level ) or approximately 1.23Vrms . Read that again ; 0VU == + 4dBu == 1.23Vrms .
Where in those measurements does human hearing or perception come into play ? It doesn ’ t . While the ballistics and slow rise time of the meter movement give some idea of the character of the audio , the VU meter is inherently an indication of what we have come to know as an acceptable voltage level for moving the relatively small AC signal known as audio . In short , VU meters measure volume .
Volume is an electronic entity . Loudness , however , is how we humans perceive one sound relative to another . You can have two songs that look the same on a VU meter while having dramatically different perceived loudness . Remember watching TV back in the day and being startled when the commercial comes in way louder than the movie you were watching ?
In fact , this is why broadcast music mixers have experience with loudness . Since the introduction of new broadcast regulations in the U . S . and Canada in 2012 , no commercial content can be louder in than the program it accompanies . This meant that broadcast materials and commercials now have to come in at a specific loudness .
Loudness is so important to streaming that all video and audio streaming services have implemented loudness requirements . That means , if you don ’ t pay attention to loudness , they will do it for you . As a mixer , you do not want that !
In broadcast environments like TV , the loudness limits are -24LUFS +/ - 2 LU . “ LUFS ” stands for “ loudness unit full-scale ,” while an “ LU ’ is a “ loudness unit .” Many have also heard of LKFS , which stands for “ loudness , K-weighted , full-scale .”
What are these and why are they important to our streaming discussion ?
These two quantities essentially refer to the same idea : that loudness can be measured based on open standards ( ITU 85.1770 to be specific ) but they are essentially the same thing . As well , a loudness unit is essentially the same as 1 dB . This allows an absolute measurement so that we can all talk about loudness using the same references and terminology .
Once television got on board , it wasn ’ t long before these concepts were used to tame the so-called “ loudness wars ” in music . In an effort to make iTunes sound consistent , Apple added the “ soundcheck ” feature in 2013 , meaning songs would be turned down by the algorithm if they were submitted louder than the allowable limit . Now all the streaming services include some form of loudness normalization : For Spotify , it ’ s -14 LUFS ; Apple Music is -16 LUFS ; YouTube is -13 LUFS ; and Tidal is -14 LUFS .
Why such differences between the TV and streaming levels ? Early on , streaming services used the TV loudness levels but identified multiple issues with this relatively quiet level . Firstly , mobile streaming devices tend to be used in noisy environments . As well , the devices ’ size prevented manufacturers from adding amplifiers large enough to provide the clean volume swings necessary to increase the listening level above these noise sources . To avoid these issues , louder levels were adopted for the streaming market .
So , having said all that , when we come back to music mixing for livestreaming and drive-in concerts , an issue becomes apparent : your mix must be loud enough to sound “ right ” over a stream , but not so loud that the streaming service will turn it down for you , because their algorithms do this work in a very non-musical manner .
The key to making this all work is your simple bus compressor and a loudness meter . For all my broadcasts , I like using the popular TC Electronic Clarity M hardware unit , but there are many popular and effective software loudness meters , such as those provided by HOFA and Waves .
Build your mix as you would normally , of course paying attention to the basics , such as proper gain staging , bus structure , and compression at the various places in your mix . As you do this , ensure you have a fairly transparent bus compressor inserted on your final output bus . For hardware mixes , I use the tried-andtrue Waves MAXXBCL , but in software , I lean toward the SSL Native Bus Compressor .
As your mix evolves , one may want to ensure the vocal is a little forward to make sure it doesn ’ t get lost . Bring your threshold up to make sure you ’ re hitting your compressor so that your dynamic range isn ’ t as wide as you normally would have it for a standard concert PA mix . Since many of the streaming specifications call for +/ - 2LU , you ’ ll notice you ’ ll have to compress fairly hard to achieve this . Use your make up gain to keep the level close to your target loudness indicated on your loudness meter .
The loudness meter has various readouts , but using the “ program loudness ” feature , which uses a rolling average across the previous 10 seconds , allows you to get a good feel for how your audio is behaving across the stream . If using a software loudness meter , make sure it is set to either “ short term ” or “ integrated ” and the scale is based on LUFS -18 LU to achieve a similar behaviour .
What you are aiming for is a mix that sounds consistent between the high dynamic passages and the low dynamic passages . The compression used here isn ’ t for effect ; the desired effect is purely level and dynamic control . Your signal should play nicely within the limits of the available dynamic range .
It takes some practice to find the sweet spot without over-compressing while still hitting the target level , but once you find it , you ’ ll notice your mixes will sound pleasantly loud enough over the stream while being well behaved enough that the services aren ’ t affecting your mix , all while still being musical and compelling .
Monitor not only through near fields but also with headphones to check what the low end is doing and how your audience will perceive your mix . As well , don ’ t forget to check your mono compatibility ! You can never assume your audience will all have properly-wired headphones and speakers connected to their phones and computers !
At one recent large multi-day festival , these principles helped provide the mixes for both streaming to the web and the on-site FM broadcast . In this case , separate output busses were used to feed the FM broadcast a level of -24 LUFS while the streaming output was bumped up to -14 LUFS . The two simultaneous broadcasts sounded full while all vocals and spoken content was clear and intelligible .
Now that we are all taking on new roles , the hope is applying these techniques may help others avoid some of the pitfalls that drive-in FM broadcasts and livestreaming present .
Wayne Hawthorne , P . Eng ., is the owner and operator of Click Track Audio ( www . clicktrackaudio . ca ), a mobile production company that specializes in high-track-count remote recording , live-to-air broadcasts , and music mixing . He is also a professor in Algonquin College ’ s Music Industry Arts program .
42 PROFESSIONAL SOUND