Bus Compression 2

my experience in this process was one which helped me discover, and then cement the approach of progressive compression

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This is my second instalment on bus compression, and the story of how I discovered what has since become my default effects chain for master bus compression.

I discussed in my last post on this topic the importance of applying compression in a staged and progressive manner through the entire sequencing and mixing process, rather than leaving all the work to a couple of plugins at the point of final ‘mastering’.  My experience in this process was one which helped me discover, and then cement this approach of progressive compression.

It centered around my track ‘Push On‘… when I’d completed mixing of this track, I was really happy with the sound… the bass line was strong and solid, and the snare and synth ‘stab’ sounds both had a nice punchy and aggressive dynamic.  What I basically wanted to achieve with bus compression was to maintain the general sound and dynamic as much as possible, while making the overall level more ‘competitive’.

My ‘goto’ compressor for bus compression is Cytomic’s ‘The Glue’, so first step was to insert an instance of this over the master mix.  Initially I used a slowish attack setting of 0.3ms, but I was finding a lot of transients were slipping through and causing digital clipping when the level was raised.  If I moved the attack back to 0.01ms, it caught all the transients, but also resulted in a fairly un-musical pumping effect.  The clips below contain 1. the track directly after mixing, and 2. the same track plus ‘The Glue’ with similar fast attack settings to what I used originally used…

Original track:

The Glue with fast attack:

The pumping of the compressor is evident from the uneven level of the offbeat open hi-hats.  While originally working on this I also noticed that the virtual ‘needle’ in The Glue jumped around unevenly, not moving with the rhythm of the track.  (From further experience since this,  I’ve come to learn that un-rhythmic movement of the gain reduction needle like this usually always results in uneven, pumping compression).

I bounced the uncompressed track to an audio file so I could get a look at the waveform (see below)…

bus-compression-pt-2-1

Notice the highlighted uneven peaks caused by the synth stab sounds (red) and snare hits (blue).  The synth stab used a fairly heavy chorus effect which caused the individual notes to peak at varying levels in the waveform.  My assumption was that at fast attack settings, the uneven peaks of both instruments were causing the compressor to trigger inconsistent amounts of gain reduction.  Coupled with the fact they were on syncopated beats of the bar (especially the synth stab which was on the 3rd 8th note), this was likely what was causing the un-rhythmic pumping of the compressor.

I used a combination of techniques to ultimately correct this, but the one which had the biggest impact was to put a limiter (Waves L1) in the signal chain before the compressor. This had the effect of evening out the transient peaks, and allowing the compressor to operate much more consistently, aswell as permitting the use of a slower compressor attack setting.  This resulted in a much more transparent compression.  The clip below demonstrates a recreation of the same signal chain…

…notice that the sound generally is much smoother, and the consistent levels of the hi hats in the original version have been maintained.

The end result was a considerable amount of compression was applied by The Glue, but it remained relatively transparent.  The final step was to use another instance of the L1 limiter at the end of the chain to bring the track up to competitive levels.  The final chain and settings were as follows…

bus-compression-pt-2-2

bus-compression-pt-2-3

bus-compression-pt-2-4

I mentioned that ultimately I used several techniques in addition to the above signal chain to achieve the result in the published version, and this included actually going back to the mix project, and applying more compression, and some limiting to the individual snare and synth stab tracks in that project (supporting my earlier comments about a ‘progressive approach’ to compression).  That meant that the first L1 instance in the master bus chain had even less work to do, and again produced an overall more transparent result.

The whole process was a really good learning experience, and the L1 > Glue > L1 effect chain has become my default for master bus compression.  If you struggle to get clean but loud results with your own master bus processing,  I hope sharing my experiences will be useful.

2 thoughts on “Bus Compression 2”

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