Using Transient Processors

Pushing The Envelope
By Mike Senior

The granddaddy of transient processors, the SPL Transient Designer hardware outboard unit, in its current MkII incarnation.

Attack‑enhancing plug‑ins can transform your mix — but they need to be used wisely!

One of the more common reasons for processing a track at mixdown is because you want to reshape its attack in some way. Your kick drum might feel like it lacks punch, say, or you want more ‘smack’ from your snare. Alternatively, maybe your percussion feels too spiky and upfront, or your piano part feels overly hard‑edged and aggressive.

Now, a lot of project‑studio owners instinctively reach for EQ or compression to address these kinds of issues, but those tools aren’t always well suited to the task. So you might try to boost your kick drum’s low midrange to add punch, but discover that this makes the drum’s tone horribly woolly into the bargain. Or you might cut some high end from the percussion to soften its attack, only to find that it now sounds dull and congested. Many producers have also noticed that slower‑attack compression can enhance a snare drum’s onset level spike (often referred to as its ‘transient’) by allowing it to zip through the processor before the gain reduction has a chance to react. However, because compressors work according to a fixed threshold level, this trick quickly becomes rather inconsistent with drum parts that have any dynamic variation to them — typically, louder hits will get more attack enhancement than quieter hits, which may not be what you want! Likewise, fast‑attack compression is often used to reduce attack, but if you try this kind of treatment on a hard‑edged piano part, you’ll rarely be able to bring the compression threshold down far enough to soften the transients of lower‑level notes without unconscionably level‑pumping or distorting the rest of the instrument’s sound.

This kind of processing incurs far less ‘collateral damage’ on the rest of the signal, because you can cut/boost just the transients, without affecting the sound’s overall timbre or dynamics.

Fortunately, there are specialist processors that can avoid many of these problems by approaching transients in a different way: not in terms of frequency response or signal level, but more appropriately in terms of how fast they cause a signal’s level to change. This kind of processing incurs far less ‘collateral damage’ on the rest of the signal, because you can cut/boost just the transients, without affecting the sound’s overall timbre or dynamics. And because a signal’s rate of level change is independent of its absolute level, transients are detected and processed the same irrespective of whether they’re loud or quiet, which means you get more consistent attack shaping when working with dynamic musical performances.

The granddaddy of transient processing was undoubtedly SPL’s original 1998 Transient Designer rack unit (shown above), and the company continue to manufacture the product to this day (albeit in an updated MkII form), as well as offering a plug‑in version. In the software domain, however, transient‑processing functionality is now actually built into many DAW systems, and even if it’s not available in your recording software, there are plenty of high‑quality cross‑platform freeware plug‑ins available, such as Kilohearts’ Transient Shaper, Flux’s BitterSweet, or Auburn Sounds Couture.

If your DAW software doesn’t include transient processing by default, or you’d just like to try out some different algorithms, there’s plenty of excellent cross‑platform freeware available, such as Kilohearts’ Transient Shaper, Auburn Sounds’ Couture and Flux’s BitterSweet.

Practical Applications

But enough of the theory. How can you get the best results out of these dedicated transient processors in practice? Well, the good news is that the main control, often labelled something like Attack, is extremely simple. Turn it up to get more attack. Turn it down to get less attack. And if all you want to do is add a bit of snap to your drum loop, or remove unpleasant spikiness from close‑miked hand claps, then you may need do nothing more than just twirl that control and trust your ears. Indeed, for at least half the transient processors I use while mixing, that’s really all there is to it!

That said, a big part of the battle is just realising that transient processing might be able to help, because its usefulness extends well beyond obvious drum‑enhancement roles. I regularly turn to it for smoothing out things like cymbal stick noise on drum overhead mics, pick noise on acoustic guitars, string slap on upright bass, or clicks and crackle on samples taken from vinyl. I’ve even used it on lead‑vocal and voiceover tracks to combat...

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Published June 2023

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