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What Is Mix Depth? How to Create Front-Back Space

by Daniel Dixon, iZotope Contributor March 12, 2019
Dubway Studios
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A sense of dimension is a key characteristic that separates professional mixes from amateur ones. Most engineers think of dimension in three ways: height, width, and depth. Height is frequency content and width is the stereo field. Depth is the front-to-back space in a mix and is a tricker area to navigate than the previous two.

Whereas some aspects of music production are driven by emotion or technical prowess, principles of depth draw on “real world” phenomena that deal with how sound moves through a space. In this article, we’ll look at how to add depth to a mix with practical tips related to EQ, timbre, reverb, and more.

Louder sounds closer

One of the more obvious ways to manipulate depth is with loudness. If we close our eyes in an outdoor space we can get a good idea of how near or far people are simply by how loud their footsteps and voices are.

A mix where all elements are the same level will sound overstuffed and quickly tire listeners. Turning down some elements while letting others maintain dominance is the starting point for adding depth to a mix and establishing tonal balance.

In pop mixes, the most important parts, like vocals and lead guitars or synths, need to be the loudest, with drums and keyboards following close behind, and additional bits like pads brought down even further in level. Electronic and other instrumental music usually place drums at the front of the mix with more flexibility for where everything else falls.

Brighter sounds closer

For something to reach the back of a mix, it not only need to be quieter than other parts—it also needs to be darker in timbre. As sound travels in nature, it loses high-frequency content to absorption by air faster than lows and mids.

Because of this, we can make things appear further away by rolling off frequencies in the upper range. To further enhance this illusion, you may want to remove some low-end too. These two moves are commonly used to create a separate space for leads and backgrounds in a vocal mix. Leads will be bright, airy, and upfront (due to a boost around 10–12 kHz) and backgrounds provide the “weight,” sitting below leads in a reduced frequency range.

Drier sounds closer

In a DAW, reverb is used to simulate the sound of a space, making it a great tool for adding depth to a mix. If we bring back vocals as an example again, modern pop and rap leads usually employ minimal reverb to appear more “in your face” than, say, folk vocals, which favor a more washed out reverberant sound. Taking a quick listen to Lorde or 21 Savage then a Grouper song will put this in perspective.

If you have a busy mix, be cautious with the amount of reverb you apply. Cranking up the wet on an instrument is more likely to muddy up a mix than give depth, so it's best to stick to reverbs with only early reflections (60–100 milliseconds), if anything. Spacious, sparse arrangements can usually handle more reverb without sucking up the space, so you can be more relaxed here, but within reason.

The delay time of reverb (aka “pre-delay”) allows us to determine the size of a space and is a key parameter for achieving mix depth. Short pre-delay times (0–10 ms) will keep the arrival of the dry signal and reverb close to emulating a small space, whereas longer pre-delay times (20–30 ms) will split the two up, so the reflection and tail arrives at an audible lag, connoting a much larger space.

When choosing a reverb to create a feeling of depth in a mix, note that it is the contrast between dry and wet elements that make some things close and others far away, not the effect itself. If too many channels are sent to a reverb you will lose all sense of detail and shape, whereas too many dry elements will come off as flat and boring.  

Finally, rolling off some of the highs on the reverb output will tame the brighter parts and cutting lows will help to retain clarity—ultimately allowing for better placement in the mix.   

Delay sounds further away

In some cases, delay proves a solid substitute for reverb to create depth. Many delays plug-ins even incorporate a subtle roll off with every repeat to mimic how sound loses high end energy over a distance, which we touched on earlier.

To start a subtle 1/16, 1/32, or 1/64 note slap delay will quickly bring depth to just about anything. Increasing repeats for a more obvious effect, especially on guitars and other plucked instruments, has an epic feel, which you can hear an example of on this Manuel Göttsching recording. Performed in a studio by Göttsching with a single guitar, the rhythmic repeats give the impression of a large stadium feel, which is a style commonly used by bands like U2 and Coldplay. Similar “delay-for-depth” effects are common in acid house and dub-related styles of music, albeit with more experimental results.

One consideration with long delays is that they can easily pile up and obscure mix depth and clarity. To avoid this, you can choose to delay just notes or words (as vocal delay “throws”) that have a space after them. This has a powerful effect on important and expressive musical moments.

Panning for depth

Although panning is a more of a “width” dimension of a mix, it can still be used to improve depth. Once you’ve added reverbs and delays to a mix, don’t just pan them hard left or hard right, but closer to the original signal that triggers them, wrapping them in depth.

For example, if the original signal is at the 3 o’clock mark, pan the reverb return to 1 o’clock and the delay to 4 o’clock. It's a small detail, but it does a better job at carving out a space in the stereo field, instead of blurring all ambient effects together in the same direction.

From the source

A basic sense of depth can be captured at the recording stage. For example, recording background vocals at a greater distance from the microphone than leads will have depth “built-in” to stems before they even hit the DAW. Recording some parts of a song in rooms with subtle ambiance, while capturing others in more reverberant spaces or “dead” environments brings in some natural variation in right from the start.

Similar concepts apply to capturing field recordings—mic’ing objects at a close distance will replicate this closeness in a track, whereas more ambient recordings taken at a greater distance are better for setting the mood of a song.  

Conclusion

Like all mixing techniques, adding depth to a mix requires a plan—you need to determine which parts of the song should be placed where, and why. A pop mix will have different conventions for EQ, reverb, and delay than a dance music mix and these need to be considered as you lay on the finishing touches. Getting depth right will greatly improve the definition and character of your music and these tips should provide you with a few experiments to get started with.

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