Adjusting Effect Levels for Mix/Bus Compression

I spent a few hours yesterday doing final bus compression for the track I’m currently working on. Approaches to and techniques for bus compression were one of the things I learnt most about during 2016, and yesterday I had a kind-of ‘lightbulb’ moment, which will hopefully lead to better results in this area going forward.

I’m a ‘reluctant participant’ in the whole competitive levels/loudness wars thing. Fundamentally I like the groove, emotion, impact, etc which a decent dynamic range can impart on a track. But at the same time I understand the need to achieve an overall loudness level that’s similar to other tracks in the same genre (especially because not doing so simply makes your music difficult for DJs to mix).

In the past, I’d always equated greater amounts of bus compression to a loss in clarity. To some extent this is true, as compression will narrow the dynamic range of the sound and hence simply reduce the ‘depth’ of volume variation available. However I’d always found that compressing the entire mix necessitated a compromise of getting closer to competitive levels while sacrificing some detail and clarity.

About halfway through last year I had a mini breakthrough of sorts, when I realised certain settings on bus compressor plugins can have a big effect on the quality of the resulting audio. Specifically I usually use Cytomic’s ‘The Glue’ as the first stage in the bus compression chain, and I found that simply setting the oversampling rate to the recommended or higher levels (4x or more when auditioning) gave far clearer audio quality than the default lower settings.

For my current track I had spent a bit longer than usual honing the reverb plugin settings, and fine tuning the reverb send levels. After this I was really happy with the result… it had a nice balance of having a good depth/space with sounding too ‘washed out’, and seemed to translate well to several different sets of speakers and headphones. But yesterday it was a bit disappointing to have some of this clarity and balance lost when I started pushing the final mix through bus compression. When I listened closely it wasn’t so much a by-product of compression, but more that the levels of the reverbs and delay effects were stronger. When I thought about it, the reasoning was obvious… I’d squashed down the top 3-6 dB of the volume range, so obviously sounds down at -15 to -20dB (like the reverb layer) had been effectively pushed up by a similar amount.

I usually do final bus compression in a separate Reaper project to the mixing, using just the final stereo mixdown as a source track (my aging PC can’t handle multiple reverb plugins and CPU hungry bus compression at the same time). So I went back to the mix project and rendered another version of the stereo mix with reverbs and main delays turned down around 1.5dB. Running this new version through the same compression chain resulted in a much clearer mix… it sounded a lot more like the former original stereo mixdown… just louder (which is exactly what I was trying to achieve).

Anyway, in hindsight I’m a bit surprised it’s taken me this long to figure out this technique (the basic point of compression after all is to reduce dynamic range), but I’m going to experiment a bit more, and hopefully end up with a lot cleaner, clearer final mix than for past tracks.

Another way to potentially prevent the issue could be to ‘mix into’ a compressor or limiter during writing/sequencing/mixing. This is a bit unorthodox technique historically, but seems to have gained popularity in the last few years (I seem to have read a lot of articles recently where people discuss working this way). The idea is to put a limiter/compressor on the master bus right from the early stages of writing (using generic/default settings close to what you’d usually use for final bus compression). This way you’re always evaluating level balance with compression already ‘baked in’. I don’t usually use this technique because for some reason I like to keep a clear separation between the mixing and final ‘mastering’ stages… but based on yesterday’s experience I can definitely see the merits, so may try it in a future track.

When the Problem is Staring You in the Face

I had an interesting experience over the last couple of weeks, with a mixing problem that should have have been obvious and easy to fix, but because I was too focused on details, I missed the bigger picture and let the problem persist for way longer than it should have.

I’m still in the finishing off stage of a track which has ended up becoming the most drawn out and time consuming piece I’ve worked on so far. I just looked back to previous posts and realised I said I was on the ‘home straight’ with it more than 2 months ago.

Part of the reason this track took longer than others was that it was the first where I’d used an acoustic instrument for one of the main themes… an acoustic piano riff (from NI’s ‘New York Grand’). As with acoustic percussion samples I’ve discussed in a previous post, any recorded acoustic instrument is inherently going to have a much greater dynamic range than synthetic sound. And to fit this into the generally very narrow dynamic of club music, considerable but careful application of compression is required.

The piano riff I came up with, I thought, had a nice dynamic… getting thicker in texture and a bit louder/stronger towards the end of the riff… I felt this gave it a bit greater feeling of tension. Although a fair amount of compression would be required to make the riff fit well in the mix, I was keen to try and preserve as much of that dynamic as possible. Hence when mixing I was too focused on trying to preserve dynamic of the riff that I’d liked in the soloed part. This unfortunately led me to being too cautious in applying compression, and ended up pushing the piano part way too high in the mix (in order to get it to stand out properly). Added to this was the mistake of not following my own advice and regularly checking back against reference tracks, so when I finally did do a side-by-side comparison with my usual reference material I’d created a kind of ‘inverted smile’ in terms of frequency spread… with piano and mid-range way too dominant, and not nearly enough bassline nor cymbals.

Once I figured out my mistake, it was pretty easily corrected with a simple application of Waves’ Renaissance Axx compressor (after having spent at least a week going in the wrong direction)… sure I had to sacrifice some of the nice dynamic I had originally wanted to highlight, but looking back, I think that original desire was misguided. The track I’m writing is in a minimal-techno style… where narrow dynamic and very loud overall track levels are commonplace… the expectation to keep a main acoustic instrument part fairly dynamic, and achieve a competitive level in the overall track was a bit unrealistic.

So 3 important lessons I learned for going forward…

  1. Audition parts in the context of a mix. Things that sound good on a soloed part may no longer sound so good, or even be completely lost in the context of a whole mix. I was too swayed by trying to work towards a soloed piano sound which I thought sounded good… it would have been better to have always auditioned it in the context of the mix right from the start.
  2. Be realistic about how much dynamic range you can achieve in styles which are innately highly compressed.
  3. Listen to and compare to your reference tracks regularly!