What are transients?
A transient is a high amplitude, short-duration sound at the beginning of a waveform. In a slightly less technical explanation: A transient is the loud and sharp section at the beginning of a sound. For example the transient section of a kick drum would be the click sound, the initial impact and would not be the low end thump that comes slightly later. Naturally a transient is the loudest part of the sound and is what gives the sound its punch or impact.
Another way to think about it is in groups of sounds you might be familiar with, here are a list of sounds that usually contain strong transients.
- Snare drum
- Kick drum
- Pluck lead sounds
- Most percussion
- Arpeggio synths
Here are a list of sounds that are not transient
- Pad sounds
- The tail end of a crash cymbal
- Buildup fx
- Atmospheric sounds
- The tail of your lead synths
Now you might be getting a bit of an idea about what transients are, what the sound like and what they feel like but...
Why do you need to think about transients during mastering?
The problem with transients and loudness is that the transient/initial impact of the sound is also the loudest part and you can see that in the first picture in this post. They stick out above the rest of the sounds and can cause alot of issues when trying to increase the overall volume of a track. For example if the snare transient is +6db louder than the rest of the music then without limiting/ compression you will always have the rest of your song -6db softer than the snare. However this issue also goes the other way. If you use limiters and compressors to turn down those transients (that is literally what limiters do, they cut off and soften the louder parts of your song in order to increase the volume of the quieter parts) you will loose the impact of all of your percussive sounds and the song will sound flat and lifeless. Limiters employ a very high ratio and a very fast attack/ release which means that only the transients (loudest sounds in the song) will be affected. This gave rise to the 'Brickwall Limiters' which were built with the sole purpose of transient reduction in the most transparent way possible which is how engineers bring up the average level of a track without digital clipping.
So how do you find a good balance between loudness and dynamics/transient retention?
The problem with brickwall limiters is that no matter how well they are designed there are still major limits to how much you can destroy your transients before the laws of sound catch up to you and the overall sound of your track begins to suffer. Alot of people have different opinions on how much you can reduce your transients before there are audible issues however personally I think that it has more to do with how loud the transients of your track are in the first place. You can have a look at the waveform of your song to get a rough idea. It is important to do it right, definitely no more than -6db of reduction so that while the beats might not have quite the same impact the mix will sound relatively unchanged while the average level (perceived loudness level: RMS or LUFS) is now 6db higher which is a very significant increase in volume.
The problem is that current practises AKA 2016 (I think 2017 will see an improvement) try to get an even louder average level with more agressive transient reduction. This results in a song that is very mushy and lifeless. There is no punch to the drums or pluck sounds, even the bassline looses its impact and groove and flattens out. AKA you begin to suck the life out of the song. If the drum transients were what was making the beat stick out, then that all-important rhythmic contribution might be compromised— "I’ve heard songs where the kick drum all but disappeared in parts of the song from over-aggressive limiting, robbing the tune of the important back-and-forth of kick and snare that’s so important to the groove". (Steven Slate 2014) If you keep lowering the limiting threshold, eventually you’ll be left with no transient impacts at all. This lack of rhythmic punch can make the musical arrangement seem like just a big wash of sound, inducing listener fatigue more quickly than anyone would want.
So now that we are all scared about killing off our transients, what can we do?
- Do not have more than 1-3 db of gain reduction on your limiter. The amount of gain reduction you see on your limiter is literally saying "how much are we squashing the loud transients of this track". So don't overdo it.
- Use compression before limiting. Using a compressor is a great way of increasing the overall volume of your track without completely crushing the transients. Compressors are basically softer limiters so set your attack and release times to let through some of those peaks and you can still dramatically increase your RMS/ LUFS level. Here is a good tutorial on maintaining transients by Dave Pensado
- Use multiple limiters, perhaps a multiband compressor. While these are just as dangerous as brickwall limiters when used poorly you can filter out certain frequencies where the transients are too sharp and bring them down by the level you choose. This means you can decrease the transients without completely chopping it off all together. Say your crash cymbal is way too loud you can filter the frequencies it is in (say 7-12k) and use the compression to compress that frequency band as the crash hits while avoiding everything else.
- Dynamic enhancement tools. There are a number of good dynamic enhancement plugins out there (Dave shows a couple in the video above) which can bring back some of that punch or even add more if the track you are working on is originally quite flat. This is usually my last resort however there is nothing wrong with using a transient shaper (perhaps in a parallel chain or with the mix/wet-dry down) to add punch back to your song. Just remember that if your limiter is after the transient shaper plugin in your mastering chain (which is should be!) you will still have the same problem if your limiter is set to "kill all transients and destroy the song" mode.
Alright guys I hope you learnt something here today. As always I would love to hear from you in the comments and if you would like us to master your song you can check out our studio here or get our FREE Mastering EQ Course and 4 Gig of presets/sampels/plugins here