I am continually surprised at how many home recordists think of the meters in their DAWs as little more than clip indicators, and that as long as their tracks aren’t clipping all is well. Some even imagine that having the hottest possible levels before clipping results in better-sounding recordings, as if they were tracking to tape and wanted to ensure maximum signal to noise.
These misconceptions about metering are the result of not understanding how digital recording relates to analog recording.
If you look at the VU (Volume Unit) meters found on a lot of analog recording gear, you’ll see that the scale ranges from -20VU to +3VU (some go higher). VU meters present the “average” level, and for various reasons the norm was to aim for an average recording level of 0VU, which in professional equipment equated to a signal level of +4dBu. For a quick refresher on the concept of dBs, see “On Tracks: What Is a Decibel?” Given that analog gear clipped at roughly +24dBu, that resulted in about 20dB of headroom beyond 0VU.
In other words, although the optimal average level was 0VU, transient peaks, which aren’t effectively indicated on VU meters, could climb as high as +10VU or so without causing problems.
Digital recording is an entirely different matter.
If you record with a DAW, you are used to seeing digital meters on mixer channels, aux sends, master faders, etc. Also known as “sample peak program meters,” they display peak levels in dBFS, or Digital Full Scale — and 0dBFS is the absolute upper limit of digital audio levels. Consequently, all of the scale degrees are minus values, such as -3 and -6 and the only thing above 0 is a clip indicator. Peaks exceeding 0dBFS, at least at the output, result in exceedingly unmusical distortion.
Obviously 0VU and 0dBFS are far from equivalent.
Setting Recording Levels to Create Headroom
In order to provide the same 20dB of headroom you get when recording at an average level of 0VU, it will be necessary to record at an average level of -20dBFS. That’s why the break point between the dark green and lighter green colors on our example digital meter is at -20. The break provides a handy visual reference. And in the same way that transient peaks could safely climb to about +10VU without incident, if your digital peak meters register peaks at about -10dBFS you’ll be fine, with a little additional headroom to spare just in case.
Note that some engineers prefer an average level of -18dBFS when recording and mixing. The scale degrees on most digital meters make it easy enough to eyeball the difference between -18dBFS and -20dBFS, but should you wish to adopt that standard it should be easy enough to adjust the breakpoint between colors to reflect that. In Pro Tools 11, for example, you just go to Preferences>Metering and change the Color Break Low parameter to -18.
If you track at lower levels the mixing levels will take care of themselves. Previously recorded tracks that are too hot may be adjusted using Clip Gain when available, inserting a Trim/Gain plugin in the first slot ahead of any other plugins, lowering the output levels of virtual instruments, etc. The idea is just to get everything in essentially the same ballpark. And, of course, nearly all of that headroom will be reclaimed when mastering.
Working with average levels at about -20dBFS or -18dBFS to provide reasonable headroom should not only yield improved results when tracking and mixing overall, it should relieve the overage anxiety that inevitably accompanies working too close to the line, allowing you to focus on more important things—like capturing great performances!
This new column will address topics of interest to recordists, ranging from remedial tutorials on essential terms and concepts (such as this one) to more advanced examples of studio geekery. Next up in On Tracks: “What Is a Loudness Meter?”
Julian Ludwig é diretor do Pro Áudio Clube, produtora de áudio Jacarandá, Loc On Demand e Jacarandá Licensing. Trabalhou para empresas como: Guaraná Antartica, TV Gazeta, NET, Chivas Regal, FNAC, Prefeitura de São Paulo, Mukeca Filmes, Agência LEW’LARA TBWA, Agencia MPM, Agência Content House entre outras. Fez trilhas para programas de TV como: Internet-se (Rede TV), Você Bonita (TV Gazeta), Mix Mulher (TV Gazeta), Os Impedidos (TV Gazeta), Estação Pet (TV Gazeta), CQC (TV Band) Vinheta Oficial TV Gazeta, entre outras. Também atuou em vários longas e curtas metragens, incluindo mixagem em 5.1 e serviços de pós-produção.