Sponsored by Eventide

Eventide Audio needs very little introduction to anyone in the world of pro audio. Their name is synonymous with high-quality effects & innovation that has been pushing the boundaries in signal processing since the 1970s. As recently documented in their must-read flashback series, the company is responsible for many sonic breakthroughs - too many to list here! - but suffice to say they introduced the world’s first digital audio effects device to be commercially available with the breakthrough H910 Harmonizer. Nevertheless, the boffins from Little Ferry, New Jersey never rest on their past glories - they are always pushing the sonic envelope and continuing to advance the tools for our craft. In 2017 they released Physion, the first plug-in to feature their “Structural Effects” technology intended to power a new line of processors, and now today there is something new & exciting happening with that engine under the hood!

Splitting the atom

According to Eventide, Structural Effects is “a method for precisely deconstructing sound”, splitting it “into two separate streams: transient and tonal. These two streams can then be independently processed, manipulated and generally messed with”. It’s an approach that is not entirely frequency-based or frequency-dependent, and instead the identification of the components is based partially on frequency and partially on time, breaking down the sound into the shapes to form the two components (transient and tonal) that are individually processed and recombined into a brand new sound. This method is also different from the usual transient shapers, which are not actually trying to structurally split a signal before processing, resulting in a less precise detection of transients, usually only allowing for amplitude or gain manipulation with inevitable bleed from the transient to the tonal portion. A good example of how this process works would be the pick’s sound on a guitar string and the sustaining note that follows it. The picked sound's spectrum is rapidly changing - it’s transient - whilst the sustaining note is steady, or slowly changing in frequency. Still with us? Here’s what that means!

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Physion Plug-In and signal flow of the Structural Effects processing

Physion, the first effect to deploy this technology, allowed us to apply two different effects to the transient and tonal elements, with a focus on classic effects such as reverb, delay, chorus, pitch-shift and tremolo - although it also offered basic implementations for compression, gate and equalization. This time around Eventide is presenting a truly specialized equalizer that takes full advantage of Structural Effects processing capabilities - SplitEQ.

To each their own curves

SplitEQ is an equalizer like no other. Currently we have many tools that can shape the attack portion of a sound, but there’s not much to be found for the follow-up part (i.e. the harmonic, or ‘tonal’ part). SplitEQ does precisely that, enabling both the transient and tonal components to be treated individually. This means that the attack and sustain of the signal can have their own, unique and distinctive equalization curve, enabling extremely precise control over each bit of the sound. Let’s take a closer look at the filter shapes or curves that are available with SplitEQ:
  • Low Shelf/High Shelf: a set of shelving-type filters with resonance (bandwidth/Q) control.
  • Tilt Shelf: this type of shelf shifts the entire signal from high to low frequencies and is used to make the sound brighter/more treble/less bass or darker/less treble/more bass. Highly useful for when a sound needs to be ‘turned around’ and an excellent way to quickly transform the overall character of sound.
  • Peak: the usual “bell” filter type with variable bandwidth that is found on parametric EQs, and alongside the shelves this is likely to be the most used filter thanks to its flexibility.
  • Notch: a narrow filter with variable bandwidth for cuts. The notch filter does not boost, and deeply cuts into the signal to the point of practically eliminating everything within its frequency range. Very useful for problem-solving, for eliminating hum or ground loops and for spotting problematic frequencies.
  • Bandpass: a filter that isolates frequencies within its boundaries. Bandpass filters are common in synthesizers and useful for sound design, but they are also handy for finding troublesome spots or isolating certain areas for further processing.

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All bands have a +/- 30 dB range for boosts or cuts, can freely be set from 10Hz to 20kHz and individually bypassed. Both gain and bandwidth settings can be separately adjusted for the transient and tonal parts. ‘Panorama’ can also be set per-band and per-transient and tonal components - for instance, the transients of an EQ band - can be panned to the right channel whilst the tonal element remains centered. SplitEQ also features a mid-side mode that works in the same way as the regular stereo, allowing the user to expand or narrow the stereo field of each band and of the transient and tonal components as well. It’s an insane level of freedom like no other equalizer out there.

Wrapping up the EQ department, Eventide has included high pass and low pass filters to give us some welcome convenience - we can tackle all the common equalization tasks with a single plug-in. These are no ordinary filters either, they have the same capabilities of other equalization bands, and are capable of individually filtering transient and/or tonal components. These filters also boast many slope options, from 6 to 96dB per octave and nearly everything in between for utmost precision.

Dealing with it at the source

A crucial component of this tool is the Split section. It starts with the “Source” parameter, which optimizes SplitEQ to work according to the nature of the input signal. There are several options to choose from here, ranging from broader references such as “Full Mix” or “General” to more specific sources for instruments including Kick, Snare, Tom, Cymbal, Full Drum Set, Electronic Beat, Hand Drum, Percussion Set, Bass, Piano/Synth, Guitar, & Vocal. If the desired source is not covered, Eventide recommends picking the closest ‘match’ based on the complexity and polyphony of the material. For greater ease of use, the Source selection can be locked when browsing the presets, making it easier to evaluate each of them under the same working conditions.

Complementary to the source selection are the Transient Separation, Transient Decay and Smoothing controls, which, alongside the source selection, will work under the hood to further optimize how SplitEQ will act upon the input signal. In general terms, Transient Separation determines where the transient ends or the tonal element begins and also affects the frequency selectivity of the transient regions. It’s a bit of a counter-intuitive setting, with larger values shortening the time window for the duration of the transient, thus producing transient regions that are more tightly defined. Conversely, Transient Decay extends that window, limiting how quickly SplitEQ will transition from transient to tonal. Lastly, Smoothing determines how fast the plug-in will split the signal, thus avoiding unwanted artefacts that may be caused during processing.

All the controls in this section are closely intertwined and there are many possible permutations between them, so it’s worth testing all of them and a helpful trick here is to alternate soloing the transient and tonal components whilst tweaking to get a better grasp of what’s going on. However, for most occasions, only selecting the desired source will suffice, so don’t worry if you never touch the Transient Separation, Transient Decay and Smoothing controls as they are more about fine-tuning than ‘mandatory’ setup steps.

Additional goodies

SplitEQ’s robust feature set comes with a handful of additional settings to provide greater ease of use and to further tweak the plug-in, including:
  • Real-time spectrum analyzer: Displays the responses of both transient and tonal components, helping users to make informed decisions when equalizing. The spectrum analyzer can be set to pre or post processing or be disabled entirely in the lower right corner, where the user will also find a menu with more settings such as source (all, split, transient or tonal), resolution (best/better for frequency or time) and decay time (very slow, slow, medium, fast or very fast).
  • Interface resizing: SplitEQ’s GUI can be freely resized, just click and drag the lower right corner and set it to taste.
  • Pan: Freely defines the panorama for each side and can be set from 100L to 100R. Default setting is center (C) on both sides for unaltered stereo. Here we can also set Mid/Side balance by clicking on the pop-up menu in the Pan label.
  • EQ Scale: Controls the amount of equalization that will be applied, from -100 to 100%. Example: if SplitEQ is set up for a 10dB boost of any filter type with Scale at 100%, it will become a 5dB boost with the Scale at 50%. Setting it to negative values from reverse the curve i.e. boost will become cuts and vice-versa.
  • Zoom: The magnifying glass on the top-right zooms in the EQ plot range scale. It also offers the additional range options for the EQ plot, which can be set 3, 6, 9, 12 or 30dB, and also “fit” to match GUI size or “full” (zooms out entirely and sets it from +30 to -60dB).
  • Info: The “i” button left of the Zoom control brings up a menu to access the PDF user guide, a link for a tutorial, enable/disable OpenGL mode for the graphics and also an option to enable/disable the tooltip - an onboard help system where you hover the mouse over each function and get a pop-up explaining that function.
  • Input/Output section: Here we have input and output levels metering, gain trim for left and right channels, and the always-handy-to-have polarity flip button. A couple of “headphone” buttons above the level meters are also available to isolate transient and tonal output.
  • Bypass: Two options available here, one that only bypasses the EQ (master section settings will still be enabled) and one that bypasses the entire plug-in.
  • Presets: Eventide has included over a hundred presets, which are neatly organised on intuitively-named parent categories such as Repair, Rebalance, Enhance, Widen or Modify, each with their own subcategories aptly named as vocals, guitars, drums, bass and so forth. SplitEQ also comes with a few preset templates for different applications such as mixing and processing individual instruments (flutes, strings, etc). Users can of course also save and store their own presets for future use.

SplitEQ is immensely versatile, with a range of application as wide as any full-fledged modern parametric equalizer (as it can be used as such) but it reaches out much further with Structural Effects to deliver unprecedented results. Individual instruments, groups or busses can all benefit when mixing, and it’s an excellent option for designing unique sounds with samples or synthesizers. It can also contribute greatly to a mastering engineer’s workflow not only for fixing or enhancing whole songs or records, but also when restoring or transferring from old formats. Here’s just a few of the many tricks you can perform with SplitEQ:
  • Boosting the transients in the mid-to-high frequency range while attenuating the tonal portion of that same region can be a great way to add presence through a more pronounced attack. Invert that instruction if a less “spiky” result is desired while keeping the presence (i.e. attenuate transients whilst boosting the tonal harmonics).
  • From the preset menu go to 02-Rebalance/Drums/Less Mud More Thud to find a perfect example of how a sound can have its low frequency punch increased without cluttering the mix.
  • Acoustic guitars can work with their namesake source profile but depending on the nature of your recording it can be worth checking out the Piano option as well. The same reasoning can be applied for synthesizers: despite the fact that they are listed as a source, they may also work with the Bass, Guitar or General profiles, depending on what kind of sound you’re working with.
  • Reach for the mid-side when equalizing the mixbus or when mastering for smooth and controlled tweaks on the stereo field, and for the panorama control when channel-dependent corrections are necessary.
  • The EQ Scale parameter is an excellent way to fine-tune the output - dial it back a bit to evenly attenuate all frequency bands.
  • As always, experimentation is key, and don’t fear the presets - if there’s any company famous for making good, usable presets, that company is Eventide!
Availability and pricing

SplitEQ is now available for the very enticing price of $99 (introductory offer - reg. $179) on AAX/AU/VST plug-in formats for Mac and AAX/VST for Windows. A fully-functional 30-day trial can be downloaded right now, so make sure to give it a go.

For more information on SplitEQ, visit: https://www.eventideaudio.com/SplitEQ