Monitor Level Calibration Secrets
Once you have marked the levels on your volume knob, take off the ear protection. Pull up an excellent reference recording, one with good headroom and transient response. These are getting hard to find in the days of the loudness race. I’ll bet it sounds great at around -8 or -9dB. Now play a current overcompressed recording and try to play it at -8 or -9. I’ll bet it sounds distorted, and very fatiguing. Here is a gestalt moment. When you find a recording that forces you to turn the monitor knob super low to not sound too loud, you’re lying to yourself about what is really going into the mix.
Now that your system is calibrated, you’ll begin to intuitively know your mixing levels. It’s even possible to mix blind, without using a meter, if you set the knob to 0dB and just mix. This allows you the freedom to leave the meters and just use your ears because the meters will never overload. Just as guitarists hear out-of-pitch strings and drummers hear wonky drumheads, your ear will start to discern these differences. As Bob Katz explains in his book Mastering Audio, “When monitor gain is calibrated so average SPL is 83dB at -20 dBFS, and you then mix by the loudness of the monitor, then the music will never overload and you will never have to look at a record-level meter!” Yes, to compete with latter-day masters, the recording will have to be mastered later, but please don’t try to master and mix at the same time. Since distortion accumulates, the better the mix you make, the better the master that the mastering engineer can make from it. (Fig. 3, below.)
Advantages Of Professional Calibration
If all this seems like too much trouble, or not worth the effort, please consider why we go through these steps. There are many advantages to mixing at a calibrated level. Most importantly, mixes will translate better across playback systems. No one wants a mix that sounds good in the club but terrible on iPods. As you need fewer revisions to dial in the final version, you’ll get better as a mixing engineer, and have happier clients. You will be able to do more projects in less time, which is good for the wallet. When dealing with fellow engineers, your mixes will travel to other studios with fewer surprises, and you will be less likely to have the mastering engineer calling to ask for a remix, adjustment, or edit. Speaking of mastering, if you provide the mastering engineer with a mix that comes in with an RMS level on average at -18dBFS to -12dBFS, he or she will be able to spend their time polishing the mixes. If the mix was monitored too low, the mastering engineer will need to compensate for the equal-loudness equalization changes that come with adding enough gain to be as loud as contemporary recordings. If the mix is too hot, the mastering engineer will not be able to use his or her gear (such as de-essers, compressors, and limiters) in the most transparent and artistically pleasing way, and the distortion will accumulate and produce a poor master when it hits the radio or iTunes. Especially iTunes since AAC is not a medium that likes hot levels. Give the mastering engineer the headroom your recording needs for his or her equipment to do a good job. These things save time, and advance your reputation as a professional, or just make your own recordings sound much better.
Finally, a calibrated playback environment can help protect your hearing, allow you to work for longer hours, and decrease fatigue. While many things in music have wiggle room for taste, aesthetic, and vision, the correct way to set up your monitoring environment is not one of these areas. There is a correct and incorrect way to do things. Do it the right way.
SPL Meters are available as standalone hardware, or for iPhone and Android phones
• Radio Shack has a great one for $49 (Model: 2055)
• iPhone users can get studiosixdigital.com/spl_meter.html
• Android users can get Sound Meter from the Google App Store
Pink Noise Signal
• You need a pink noise signal calibrated to exactly -20 dBFS RMS level. I suggest you download a test file from: digido.com. Register (it’s free), and go to the downloads section.
• For the time being, the built-in knob on your interface can work. Better fidelity, more features, and ergonomics can be had with the Kush Audio Main Gain: store.wavedistribution.com/kush-audio/main-gain.html
• More features for larger setups in an analog system: dangerousmusic.com/stsr.html
• If your budget permits, an industry flagship is the Crane Song Avocet: cranesong.com/avocet.html
Crest Factor — the difference between the average level of a recording and its peak level. Also look for the new term, which has been coined by the PLOUD group at the EBU, “PLR,” known as “Peak to Loudness Ratio.”
Sound Pressure Level (SPL) — measures sound intensity relative to a reference value. Sound pressure or acoustic pressure is the local pressure deviation from the ambient (average, or equilibrium) atmospheric pressure caused by a sound wave.
Level — a measure of sound intensity. However, it must accompany another defining term — otherwise it doesn’t mean anything. (e.g. Voltage Level, Sound Pressure Level).
RMS Level (Root Mean Square Level) — the average level of program material. Humans tend to hear things on average levels versus peak levels.
Peak Level — a maximum level of signal in a sound program. In digital audio, this peak level is usually noted in relation to how far it is from the maximum celling of 0. For example, a -2 peak is 2 decibels lower than the maximum 0 dBFS.
dB — a relative quality of sound compared to a reference.
dBFS — decibels full scale in a digital PCM system. This is the max level a digital recorder can encode or playback.
Fletcher-Munson Curves — often used to mean equal loudness contour curves. Named after the researchers who first widely published research indicating human hearing is not linear with respect to frequency.
Volume — is a term invented by marketing people for the name of the knob that makes things louder and softer. It has no precise definition in audio engineering.
For More Information
Katz, Bob. Mastering Audio: The Art And The Science, Second Edition.
Although the title suggests this is a book for mastering engineers only, over half of the text is devoted to digital audio fundamentals. I consider this a must-have reference book for anyone running a digital audio workstation. This is a reference that should come with every new DAW.
Brixen, Eddie. Audio Metering: Measurements, Standards And Practice / Edition 2
For a more detailed look at measurements, applications, and use across industries, Brixen’s book is considered one of the best reference books by broadcasters around the globe.