Calibration is super important in any recording studio. Acoustical engineering is a massively complex process that the majority of audio professionals never even delve into. We know the basics – things like treating our walls, filling out corners with bass traps, and avoiding standing waves as much as we can, but that’s just the start of where room design can go.
In other ways, audio professionals are used to calibrating every day. Everything from adjusting your listening position to tuning a guitar to dialing in an amp is a form of calibration. You’re calibrating your equipment to sound it’s best and while it may not feel like it, you’re calibrating every step of the way.
But aside from the settings of your various hardware and software, there’s a certain amount of calibration needed just to get your equipment performing at its peak. Today, we’re going to look at compression and why the right calibration makes such a huge difference.
Calibration is super important for compressors in particular because of how they function. While every part of your signal chain is going to have some variances based on how they’re configured, none rely as heavily on the amplitude of your signal as a compressor. After all – the level of your signal is what ultimately triggers the compressor and causes it to start acting on your signal!
In the box, there’s not a lot we need to worry about here, at least not as much as in the outboard world. Everything in your DAW is going through internal routing and most plugins give you very limited calibration controls (if any). Loading up two instances of any compressor plugin is going to result in the same exact default calibration settings across both instances.
But for hardware, there’s not that same baseline to start from. In fact, short of running two tracks through the same compressor on different passes, you’ll probably never get perfect balance between two hardware units. Our goal is just to get them as close as possible so that the two units work just as hard as one another with the same amount of headroom and range.
How To Calibrate Hardware Compressors
Calibrating hardware compressors requires multiple tools and a bit of technical expertise, but it’s fortunately not something you should have to do often. If you’re not comfortable opening up and working with your electronics, having a tech calibrate your setup is likely the better option. Setting the right calibration once should last you years unless one of your compressors needs to get serviced.
Essentially, you’ll need to have a digital multimeter (DMM for short) and some small screwdrivers for most compressor adjustments. Look up your particular compressor for detailed instructions.
In most cases, calibration is as simple as running a 1 kHz signal into your compressor, then measuring voltage at various points in the circuit. Commonly, manufacturers will include internal potentiometers (pots) at several stages that allow you to fine tune and adjust as needed. These pots are identical to the knobs on the front of your gear, but because they don’t control common characteristics that you’d want to adjust often, they’re kept inside the unit.
These pots control things like the Q bias, input/output trims, and meter sensitivity. Some more advanced units even give you control over the amount of Total Harmonic Distortion (THD), but adjusting that to any level of technical specificity is going to require some additional equipment.
Setting your compressors to manufacturer spec is often the best way to go unless you really know what you’re doing. By setting it to spec and matching your units to each other, you’ll be able to hit your compressors exactly as they’ve been designed to handle audio.
Gain Staging – The Final Calibration
One of the last things that often gets overlooked when working with compression is the importance of proper gain staging. Gain staging is simply supplying your compressor with optimal levels and outputting a level that’s optimal for the next stage of your chain. Messing up either can have some serious impact on your mix.
Every piece of outboard gear and every plugin has a target range where they’re going to work their best. With software in particular you’ll want to be especially conscious of this. Unlike hardware which can often saturate and harmonically distort when the input threshold is exceeded, software doesn’t react quite as nicely.
But when you treat your compressor as just one stage in an overall chain of processing, it can sound amazing. Just take a listen to this example from Ice Nine Kills’ Justin DeBlieck:
As you can see in the video, there’s a lot of different vocal tracks going on at once, but they’re all hitting Gain Reduction 2 with plenty of headroom and sound incredible when summed back together in the mix!
If all of this feels like a bit much for something like a vocal chain, there are other options out there that will sound amazing and save you the worry of proper gain staging between plugins.