Recording Tips
ROB LONG CRACKS THE CODE TO COMPRESSORS.
Selecting and applying compressors is one of the most daunting yet creative tasks in the studio. It's daunting because there are so many possibilities, and because it appears to be such a technical process which is critical to ‘ get right’. But on the flipside, any process with so many variables just has to be full of creative potential!
This is part one of a two-part look at compressors and their various usages. In this one, we'll take a look at the types of units currently available to the masses – in the ne xt edition, we'll discuss the wide range of potential usages in detail.
Generally, it’s fair to say that most musicians tend to get the hang of EQ and reverb early on, as they are the most commonly found effects found on guitar amps and small PA systems. Compression is not in every guitar player’s kit, as it tends to work better for some playing styles than others. Compression on a small PA desk can be used judiciously with great success, but can certainly complicate things in the wrong situation. If there are feedback issues from poor mic or speaker positioning, or from other reflections in the room, compression will often magnify the issues.
There’s a world of difference between using a stompbox compressor on a guitar and patching a studio compressor over a guitar amp mic. The stomp pedal interacts more with the player, and the way the part is played before the guitar is even amplified. The mic/amp compression, on the other hand, interacts more with the room and atmosphere that the amp is in.
Not everyone has had the opportunity to apply or explore the possibilities of using compression on live drums, but most people playing in bands have probably heard the effect of recording a jam or rehearsal through a phone, camera or other small device with an inbuilt condenser mic. You’re doing well to hear anything other than drums, as the compression effect from the
circuitry crushes everything into a wall of sound. It may sound a little crunchy and chaotic, but there’s an undeniable energy and excitement created by the interaction with the compressor, and this is one reason compression can be such a creative tool when it's used correctly.
Even for those who are recording regularly, very few actually get the chance to work with the real-deal hardware compressors that many plugins are modelled on. Even if they did, it would take years to master them and understand the nuances between units.
Nevertheless, getting a thorough understanding of the various types of compressors, their designs, characters and typical applications is still relevant even when using mainly digital versions.
When you tell people that compressors and limiters are used to reduce dynamic range – for example, the span between the softest and loudest sounds – they tend to interpret that as the last thing they’d want done to their songs. But the reality is that most music we hear has at least a basic level of compression, through to the heavy handed. Compression is necessary to control maximum levels and maintaining higher average loudness, at least at the mastering stage.
Obviously, over-compressing your music can flatten things out too much and create an unpleasant crunch. But used subtly, it'll make everything more natural sounding and intelligible without adding any unnecessary distortion, resulting in a smoother mix which ‘ glues’ everything together.
Additionally, many compressors will have a distinctive colour which can inject some character and energy into your tracks. There’s a common set of parameters and controls common to most compressors, though obviously things vary from model to model.
THRESHOLD
When a signal passes above the set threshold, it will be compressed. Any signal under the threshold level will pass unprocessed. Thus, if you set the threshold high, most of the signal will pass uncompressed. If it’s set low, most of the signal will be compressed. When all of the signal is being compressed, it’s known as ‘limiting’.
ATTACK TIME
Once the signal reaches the threshold point, the time it takes the compression to be applied depends on the attack time setting. Attack times between 20 and 800 microseconds are considered fast, whilst slower times generally range from ten to 100 milliseconds.
KNEE
The 'knee' of a compressor is simply the transition from the non-compressed to compressed states of the signal running. Compressors are often designed to perform either soft or hard knees, though many are switchable, making them more versatile.
Some units provide even more flexibility, allowing a selection of any position between soft and hard. As you’d imagine, a ‘ soft knee’ produces a smoother and more gradual transition to compression than a ‘hard knee’, but both have their applications.
RELEASE TIME
This is simply the time it takes for the compressed signal to return to the original uncompressed signal level. Release times are usually longer than attack times, and can range from five milliseconds to five seconds. The classic compression “pumping” effect is heard when a heavily compressed signal has the release time set very short, causing a cyclic activation and deactivation of compression. This is a very interesting effect, though it's one that will often sound very ugly in the wrong circumstances.
RATIO
The ratio specifies the amount of attenuation to be applied to the signal, and is usually expressed in decibels. To clarify, a ratio of two-to-one indicates that a signal exceeding the threshold by two decibels will be attenuated down to one decibel above the threshold.
OUTPUT GAIN
Because compression attenuates the overall signal by setting a threshold, it’s usually necessary