Space Is the Place, Part 2

Jan 1, 2009 12:00 PM, By Myles Boisen

OPEN UP YOUR MIXES BY AVOIDING "SPACE INVADERS"

In part 1, I explored methods for enhancing clarity and space in mixes by thinking conceptually in three dimensions: horizontal (left to right), depth (foreground to background, as governed by volume of individual elements), and vertical (frequency). I also addressed reverb and how it can be used to enhance space or overused to fill up too much space. (Read part 1 in the December 2008 issue, available at emusician.com.)

In this installment, I'll address additional methods to open up your mixes and create truly 3-D results. I'll show you how to avoid common problems such as overuse of compression, overly dense arrangements, and misapplied equalization. Such “space invaders” are problematic enough on their own, but when more than one is present in a mix, complex interactions can occur that may smother and overwhelm what were once well-recorded tracks.

Squeeze with Care

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When used judiciously, compression is a powerful tool for holding expressive tracks like vocals and instrumental solos in one dynamic place rather than letting their focus slide between the foreground and background. But as with reverb, too much of a good thing can be harmful, and you can end up with an overcompressed production that doesn't breathe dynamically.

Compression becomes a space eater particularly when it is overused on percussive and low-end elements, especially electric and acoustic bass. During consultations for remixing (in the old-fashioned sense of the word) and mastering, one of the things I most often recommend is to remove or reduce compression on percussive and bass instruments.

In the depth dimension, percussive sounds generally exhibit sharp transients that are heard initially in the foreground or midground and then fade rapidly into the background. Functionally this kind of movement is very important because it punctuates sustained sounds and reinforces a feeling of space and propulsion in the depth dimension. Overcompression dilutes attack and punch, and obscures rhythmic relationships by inverting the natural dynamics of a percussive event (see the sidebar “Compression: Don't Overdo It”).

For instance, when low drums have a noticeable decay or a dominant note (or both), compression can intensify tonal components, eating up space and adding muddiness in all three dimensions. Increasing sustain in the low range can create dissonance, beating, or competition with bass instruments, especially when combined with reverb.

Likewise, remember that bass — whether acoustic or electric — fulfills a percussive and timekeeping function in many musical styles. Moderate compression helps keep the bass present and consistent. But overcompressing it sabotages its rhythmic role, boosts muddiness and tonal competition, and can create a variety of problems during mastering.

As with reverb, the origin of space-sucking compression abuse is often a lack of familiarity with parameter adjustments, or a blind reliance on default settings. In particular, failing to alter a compressor's attack time from a default zero setting will make almost any kind of track sound overcompressed and lacking in transients.

Mixes that sound flat can often be revitalized by examining and increasing attack times of compressed tracks to 10 ms or more. This adjustment not only passes initial transients — which are vital to vocal intelligibility and percussive attack — but also lessens gain reduction generally to restore depth and dynamics (see Web Clips 1a and 1b).

Another way to breathe dynamic life and space back into your productions is to utilize stereo-mix-bus compression as an alternative to compressing many individual tracks. To preserve spaciousness and dynamics, my mixes use light compression on individual tracks only where necessary (usually kick drum and vocals, sometimes bass, guitar, or instrumental solos), combined with moderate stereo-bus compression. A third compression level of digital peak limiting is added during mastering. The cumulative effect of three small compression stages — rather than piling on the compression all at once in mixing — works well to preserve the liveliness and dynamic depth of background and midground tracks.

To avoid adding coloration or extra noise, I recommend using a sonically transparent, high-quality hardware compressor or plug-in for the demanding task of mix-bus compression. As a starting point, recommended parameter settings include a low ratio (2.5:1 to 4:1), a slow attack (10 ms or more), a fast release (200 ms or less, depending on tempo and musical style), and a soft knee. Set the threshold so that maximum gain reduction is only 2 to 4 dB, then adjust to taste from there. Adjust makeup gain so that the highest peak gain levels reach -2 dBfs or lower, to allow some headroom in mastering (see Fig. 1).

The main point is that compression causes problems when it limits or eliminates the depth dimension, crowds out space in the horizontal (imaging) dimension, inverts the natural dynamics of percussion and bass, and increases low-end competition and mud. Too much compression also puts all frequencies in your face, forcing the ear to prematurely tune out the subtleties of space and dimensionality as listening fatigue takes over. Overreliance on compression also increases the general noise floor of your mix. Even at low levels, noise obscures the ear's perception of background details that contribute so much to the unique spatial qualities of a mix.