Mixing Secrets For The Small Studio - Additional Resources
Chapter 13: Frequency-selective Dynamics
Workflow Demonstration Video
(To download all WAV examples at once: 136MB ZIP)
Equalising Parallel Dynamics Channels: As long as you’re wary of phase-cancellation issues, you can create a wide range of frequency-selective dynamics effects simply by equalising parallel dynamics processors. For example, in Mix Rescue November 2008 I wanted to add lower-midrange warmth and sustain to an acoustic guitar Ex13.01: WAV/MP3play_arrow. A normal parallel compression treatment Ex13.02: WAV/MP3play_arrow added the warmth/sustain attributes that I wanted, but also in this case overemphasised high-frequency mechnical noises. Cutting high frequencies out of the compressor return channel focused the compression effect more into the required frequency range Ex13.03: WAV/MP3play_arrow. By way of contrast, here’s an example of the opposite situation from Mix Rescue July 2008, where a piano part Ex13.04: WAV/MP3play_arrow was lacking in high-frequency sustain – a common problem for pop/rock mix applications. Adding in an HF-heavy parallel compression channel Ex13.05: WAV/MP3play_arrow resulted in a timbre with more high-frequency sustain Ex13.06: WAV/MP3play_arrow. Another application of high-frequency parallel compression is adding brightness without overemphasising sibilance. For instance, the vocal from that same Mix Rescue project Ex13.07: WAV/MP3play_arrow was already sibilant enough as it was, but adding in an HF-only parallel channel like this Ex13.08: WAV/MP3play_arrow allowed me to brighten things up without the ’s’ and ’t’ sounds sand-blasting my ear canals Ex13.09: WAV/MP3play_arrow. Of course, compression isn’t the only dynamics process which can be used in a parallel configuration – gating has its uses too. For example, the kick drum in that same Mix Rescue project Ex13.44: WAV/MP3play_arrow is given controlled presence and weight by mixing in this parallel gate channel Ex13.45: WAV/MP3play_arrow. Here’s the final mixed tone Ex13.46: WAV/MP3play_arrow, complete with a little of that mix’s short blend reverb.
Side-chain EQ For Full-band Dynamics Processors: The most common applications for this are in gating. For example, here’s a snare-drum close-mic recording which captured a lot of spill Ex13.12: WAV/MP3play_arrow. Spill can often work in your favour when mixing drums, but assuming for the sake of argument that you wanted to use a simple gate processor to remove it, you’d quickly encounter difficulties getting the gate to trigger correctly. When the threshold is set low enough to let through all the wanted snare hits, the kick and hi-hat spill elements also trigger the gate to open sporadically, as in this example Ex13.13: WAV/MP3play_arrow – I’ve kept the attack and release times fairly fast so that you can easily hear the triggering action. This is where filtering the gate’s side-chain can help out: high-pass filtering at 670Hz stops the kick interfering with the gating Ex13.14: WAV/MP3play_arrow, while a low-pass filter at 4.8kHz protects against the hi-hat Ex13.15: WAV/MP3play_arrow. It’s important to realise, however, that none of this filtering has any effect on the tone of the audio signal passing through the gate, because the filters only affect what the gate’s detector circuit is hearing. Equalising the side-chain signal of a compressor can also be useful for adjusting its sensitivity to certain frequencies. One of the most common scenarios for this is when de-essing. For instance, here’s a sibilant vocal which requires de-essing Ex13.16: WAV/MP3play_arrow, and here’s what it sounds like after it’s been processed with such a de-essing compression setup Ex13.17: WAV/MP3play_arrow – full details of the settings can be found in Mix Rescue August 2009.
Some Hiss-reduction Strategies: While full-band expansion/gating can deal with noise in the gaps between notes, it’s powerless to handle hiss overlaid on the wanted audio, as in this example Ex13.47: WAV/MP3play_arrow from Mix Rescue February 2007. Fast low-ratio, low-threshold expansion of the high-frequency band can usually achieve around 6dB of hiss reduction without too many undesirable pumping artefacts Ex13.48: WAV/MP3play_arrow, but you’ll need a dedicated spectral expander to take things any further, as in this example Ex13.49: WAV/MP3play_arrow, which was processed with Voxengo’s Redunoise 32‑bit .
Multi-band Compression At Mixdown: Multi-band compression can help balance different frequency regions of a single sound, and is a surprisingly common requirement for small-studio mixes, especially where the monitoring system’s low-frequency response is unreliable. In Mix Rescue July 2010, for instance, the supplied synth part Ex13.18: WAV/MP3play_arrow was rather uncontrolled in the sub-150Hz region, and it was only by compressing this section of the spectrum separately with multi-band processing that I was able to confidently increase the power at the low end without headroom difficulties Ex13.19: WAV/MP3play_arrow. Acoustic guitar parts are also a frequent target for multi-band compression, as a means of controlling high-frequency pick noise. Here’s a slightly dodgy-sounding acoustic guitar part which could use a bit of that kind of attention Ex13.20: WAV/MP3play_arrow. Although you can knock off some of the excess picking with simple fast compression Ex13.21: WAV/MP3play_arrow, you can improve things even further by aiming this remedy just at high frequencies using a multi-band compressor Ex13.22: WAV/MP3play_arrow. A similar troubleshooting scheme can also work against overprominent stick noise in drum recordings. In Mix Rescue July 2010, for example, the overhead mics Ex13.23: WAV/MP3play_arrow have occasional spiky stick noises on the ride cymbals, exacerbated by the heavy compression which has been deliberately applied for artistic effect. Fast, hard compression at the top end smooths off these unwanted corners Ex13.24: WAV/MP3play_arrow.
Multi-band Transient Processing At Mixdown: Multi-band transient processing can also deal with guitar pick noise very effectively, as demonstrated in Mix Rescue April 2009 (before transient processing Ex13.25: WAV/MP3play_arrow; after transient processing Ex13.26: WAV/MP3play_arrow). However, the thing I find this kind of processing most useful for is adding low-frequency punch to kick-drum sounds, as in the following examples, the first from Mix Rescue August 2010 using Voxengo’s Transmodder 32‑bit (before Ex13.27: WAV/MP3play_arrow; after Ex13.28: WAV/MP3play_arrow) and the second from Mix Rescue February 2009 using Waves TransX (before Ex13.29: WAV/MP3play_arrow; after Ex13.30: WAV/MP3play_arrow). In both cases you get a lot of extra low-end power, but without any messy low-end rumbling.
Dynamic EQ At Mixdown: Like multi-band dynamics processing, dynamic EQ has the ability to deal with balance problems between different frequency ranges of the same recording. So, for example, in Mix Rescue June 2008 the drum submix from a live gig Ex13.31: WAV/MP3play_arrow has the hi-hat was coming through rather too strongly, on account of spill through the snare mic, but gating the snare mix itself turned out to be too intrusive a processing approach because the snare mic’s spill contribution was important to the sound of the kit as a whole. Expanding the submix’s high frequencies with a dynamic high shelving filter proved to be a more successful approach Ex13.32: WAV/MP3play_arrow. Where dynamic EQ really comes into its own, though, is where the dynamics of very narrow regions of the spectrum need modification, as in this bass recording Ex13.33: WAV/MP3play_arrow, where the notes are rendered very uneven-sounding because of the wayward dynamics of the note fundamentals. Compressing the worst offenders with a couple of extremely narrow dynamic EQ bands was just about the only way to smooth things out Ex13.34: WAV/MP3play_arrow – check out Mix Rescue May 2010 for full details of this particularly thorny processing problem. The most common application of narrow-band dynamics treatments like this, though, is in dealing with vocal harshness, and here are a couple of different examples of this kind of processing in action. The first is from Mix Rescue January 2008, featuring a female singer: without dynamic EQ Ex13.35: WAV/MP3play_arrow; with dynamic EQ Ex13.36: WAV/MP3play_arrow. The second example comes from Mix Rescue December 2009, featuring a male singer: without dynamic EQ Ex13.37: WAV/MP3play_arrow; with dynamic EQ Ex13.38: WAV/MP3play_arrow. In both cases, notice how its only on certain more strained notes that the harshness becomes a problem, so it’s not something that can be dealt with just using normal static EQ.
De-essing At Mixdown: Using a de-esser on vocals shouldn’t really be rocket science. If you’ve got a vocal with too much sibilance Ex13.39: WAV/MP3play_arrow, as in Mix Rescue November 2008, then use EQ (or the de-esser’s built-in ‘listen’ mode) to find the most shrill frequency, and then dial in just enough gain reduction to tame the problem Ex13.40: WAV/MP3play_arrow. The main thing to beware of is over-doing the gain-reduction, as this can suck the life out of the vocal and may even make the singer sound like they’re lisping Ex13.41: WAV/MP3play_arrow. Bear in mind, though, that the simple dynamic EQ circuit at the heart of many de-essers can sometimes be useful on other instruments than vocals. In Mix Rescue February 2007, the pick noise on this acoustic guitar recording Ex13.42: WAV/MP3play_arrow, for example, was tackled with a de-esser in the absence of more powerful tools, helping to bring about this final remixed sound Ex13.43: WAV/MP3play_arrow.
Affordable Multi-band Compression/Expansion Plug-ins: There are now plenty of dedicated multi-band dynamics plug-ins available. As far as freeware is concerned, I’d recommend Cockos ReaXcomp, GVST GMulti, and Sonic Anomaly QuadraCom. If you want linear-phase crossovers, check out DDMF’s affordable LinComp, and Melda’s reasonably priced MDynamicsMB is also worth a look if you need maximum flexibility.
DIY Multi-band Processing: If you’re working on a budget, or simply find that available ‘one-stop’ multi-band processors won’t do what you need them to, then you can always implement your own multi-band processing setup using crossovers and multiple full-band processor plug-ins. This is easy to do in Cockos Reaper, for example, using the 3/4/5BandSplitter and 3/4/5BandJoiner algorithms in the ReaJS plug-in in conjunction with Reaper’s multi-channel routing capabilities, as explained in this article. If your own DAW doesn’t have the same flexibility and crossover functions, try a separate effects-matrixing plug-in such as DDMF Metaplugin, Kushview Element, or Plogue Bidule. Whichever way you implement it, though, do be wary of the possibility of phase mismatch between the bands if plug-ins with different processing latencies are used.
Affordable Multi-band Dynamic Noise Reduction Plug-ins: The only freeware multi-band noise-reduction processor I know if is Cockos ReaFIR (using its Subtract and Gate modes). If you need something more flexible for broadband noise, try Voxengo’s affordable Redunoise 32‑bit . If clicks and crackles are also a problem, then try Izotope’s affordable RX Elements.
Affordable Dynamic & Spectral Equaliser Plug-ins: The only decent freeware options I know of here are Tokyo Dawn TDR Nova and Cockos ReaFIR (using its compressor mode). If you’re willing to spend a little money, check out Toneboosters ridiculously affordable Equalizer, Voxengo GlissEQ, and Melda MSpectralDynamics. Cockos ReaFIR is also a workable option for reducing resonant peaks, although I personally prefer Sknote’s affordable SoundBrigade.
Affordable Dedicated De-esser Plug-ins: While you can achieve de-essing in many different ways with other processors, here are some freeware one-stop plug-ins if you need them: Airwindows DeEss, Dead Duck DeEsser, and Sleepy Time DSP Lisp.
Frequency-selective Dynamics In Practice: I use a lot of frequency-selective dynamics processing for salvage purposes in Mix Rescue, but here are some specific examples that are particularly worth looking over. In Mix Rescue July 2008 I demonstrated a number of different frequency-selective processing strategies based around equalised parallel dynamics channels. In Mix Rescue October 2009 I delved into the practicalities of DIY multi-band processing for a number of the sounds. And Mix Rescue June 2010 deals with some in-depth specifics of mastering-style full-mix processing using high-spec multi-band processing.
More Information On De-essing: Here’s a whole article dedicated to the subject of de-essing in its many forms: ‘Techniques For Vocal De-essing’. It includes a downloadable Cockos Reaper project file that demonstrates the mechanics of six different de-essing methods.
Source-separation Software Options: Where the mix problems with a recording file prove insurmountable with traditional mix processing, then specialist restoration and sound-extraction software may be the answer. For a good overview of the options and possibilities here, check out Christopher Kissel’s monotostereo.info web site. Although the site is officially concerned with upmixing mono mixes to stereo, the technology involved has many mix-salvage rebalancing applications.