Finding the Sweet Spot for Compression
Every compressor has a sweet spot. Depending on which one you’re working with (and the purpose for which you’re using it), that spot might be vastly different. But make no mistake – it’s there and finding it can make or break a mix. Seriously.
The sweet spot is what makes every compressor unique. Depending on the circuitry and signal routing, compressors react differently to incoming sounds. Some of them are great at catching transients – clamping down the instant something crosses their threshold. Others are better suited for adding saturation to your signal – introducing some harmonic distortion along the way.
And still more compressors are flexible – allowing you to switch between various compression modes to react differently in different situations. The amount of sheer customization out there today makes it more useful than ever to know how to find the sweet spot, especially when it’s such a fluid, moving target.
Finding Balancing with the Sweet Spot
If nothing else, the sweet spot of many compressors help you find balance as you work. Monitoring the input of your compressor, you get instant visual feedback when you hit your compressor at an optimal level – ensuring that your peaks are hitting the compressor at the perfect amount for it to work efficiently.
For most hardware, this nominal operating level is somewhere around 0 dB on your VU meter on input. It’s at this point that your signal has enough headroom to avoid clipping/distortion, but enough signal to prevent the noise floor from creeping up and causing an issue as compression is applied. This concept is commonly known as signal-to-noise (S/N) ratio; the higher your signal-to-noise ratio is, the harder you’re going to be able to press your compressor without a noise problem.
Naturally, if there’s a sweet spot for input, there’s also going to be one for output. It’s perfectly fine for a sound to leave a compressor with a different signal level than it entered, but to avoid tricking themselves with a mismatch, many engineers choose to level match their input to their output. Essentially, by monitoring the amount of gain reduction the compressor is applying, engineers can raise their output gain level by a proportionate amount, offsetting any change in level. Following proper gain staging techniques, this makes it so the compressor imparts its effect/color on the signal without drastically changing its level – preparing it perfectly for whatever’s next in your signal chain.
Instrument-Specific Sweet Spots
While many compressors have optimal operating ranges, there are no hard-and-fast rules you need to follow when working with them. Many engineers choose to work with a few stock compressors that they know well across all of their sources while others have a dedicated compressor preference for each instrument. Compressors can be used for their coloration and character as much as they’re used for dynamic control, which adds a whole other aspect to consider.
Take for example the LA2A – one of the most legendary vocal compressors of all time. The compression applied by the unit is usually very transparent. It works off of a fixed threshold (read: fixed sweet spot) and only 2 knobs: one for input gain and one for peak reduction. Engineers love using them during tracking because they’re considered softer and more forgiving than other compressors while still resulting in a massive sound.
But that doesn’t mean you can’t get a more aggressive tone out of them. Simply driving the input hotter or adding more drastic peak reduction can give more aggressive results. This is the exact concept behind our dynamics plugins too – the harder you drive them, the sweeter they sound!
Using Audio and Visual Feedback
As much as we love saying “trust your ears”, the truth is that visual feedback can be just as good an indicator that something is working as you intended it too. Sometimes you just want to take 2 or 3 dB off your peaks – a gain reduction meter is perfect for seeing that in action. No guessing and quicker results.
This is especially handy when you’re trying to match two or more compressors with each other.
Other times, the benefits of visual feedback are more of a hint that something’s working right. One of the most popular settings for SSL-style bus compression is to get it to “just barely move the needle”. These compressors only show gain reduction, but because the smallest amounts of reduction are hard to see (the meter starts marking reduction at 4 dB), simply moving the needle is enough to see that something is happening.
In practice, bus compression doesn’t need a lot of reduction to have a noticeable impact on your overall mix. It acts more like a glue than anything else.
Simple Solutions Work
As I mentioned in the LA2A example, sometimes simple solutions are the best options out there. When you eliminate the sometimes-overwhelming aspects of a plugin or processor that makes them more adjustable, you end up with a user-friendly product. It’s why Gain Reduction Deluxe is stripped down to only the essential controls and Gain Reduction 2 focuses on changing specific characteristics of a vocal.
What’s your favorite simple solution to common mix problems? Come share your experience with the JST Forum on Facebook and see what others are saying too!