Bus Compression 3

Back in October last year I wrote a post about bus compression, and what at that time was my default effects chain for master bus compression. Some time’s passed since then, and my standard master bus effects chain has evolved further, and using this chain and new techniques I’m now able get pretty significant level increases (5-6dB) whilst still maintaining a reasonable transparency and general mix clarity.

New Plugin

The biggest change to the setup is the final limiter plugin. Previously I was using Waves L1 for this, and whilst it’s a useful tool, and definitely very good for transparent limiting on individual sounds, it’s also getting pretty old (not sure exactly when it was released, but it was more than 12 years ago), and I find that across a whole mix, it tends to add artefact, and lose some transparency when more than around 3-4dB of gain reduction is applied. After looking at a couple of different options as a replacement, I bought the T-RackS Stealth Limiter after reading a couple of favourable reviews. I have absolutely no regrets about this… the amount of gain reduction it can provide without any adverse artefact is quite amazing (this was one of the reviews that convinced me incase you’re interested).

Effect Chain

I’ll go through the exact effect chain and settings I used on Cantana 2. In the previous post I discussed using Waves L1 as the first step in the chain, to even out transients and allow subsequent compressors to work more easily… and this aspect hasn’t changed. In Cantana 2, I used threshold of -3.5dB, with the fastest release setting, just to catch and even out the really fast peaks…

bus-compression-3-1

Another significant change is that I now tend to use two instances of Cytomic’s ‘The Glue’ in series. The main difference between these two instances is in the attack and release settings… the first tends to use quicker settings in order to further (but more gently) even out peaks, whereas the second uses slower attack and release to provide a smoother, more general gain reduction.

For the last couple of tracks, I’ve used parallel compression in the first Glue instance… using a high ratio and low threshold to really squash the sound, and then using the dry/wet control to blend it back with the original signal. The settings used for Cantana 2 are shown below…

bus-compression-3-2
Threshold: -17.8dB
Makeup: 3.8dB
Mix: 12%

One thing I’ve found with parallel compressing in this way, is that it’s easy to either compress the wet signal too much, or blend too much of it back, and adversely change the level balance of different instruments in the mix. I had this problem with Cantana 2 initially, where the snare/clap sound in the original mix was still quite dynamic and peaky… this meant that the low threshold / high ratio settings tending to really squash the snare and introduce ‘unmusical’ pumping. When blended back with the original signal, the net effect was that the level of the snare dropped in the mix (sounded very similar to dropping the snare level by 1-2dB in the original). I fixed this by going back to the original mix project, and adding a bit more compression to just the snare track… this reduced the peakiness, and allowed The Glue to compress the whole mix more smoothly. Still I was surprised that the difference between what I considered the ‘right’ setting for the threshold, and having too much compression was only roughly a couple of dB, as the two clips below show (in these, the first Glue instance is set 100% wet for demonstration… 12% of this was mixed  back with the original signal in the final settings)…

Threshold: -17.8dB

Threshold: -19.8dB, Makeup gain increased to level-match. Notice the drop in level/clarity of the clap/snare, and pumping effect on the piano part.

The second instance of The Glue used a lower ratio, and slower attack and release (release set to the ‘Auto’ setting). This created a kind-of ‘continual’, general compression over the mix, to give a couple of extra dB of gain reduction…

bus-compression-3-3
Threshold: -14.2dB
Makeup: 3.2dB

One interesting comparison between the instances of The Glue, was the movement of the virtual ‘compression’ needle in the UI. The needle in the first tended to move quite quickly in response to the dynamics and rhythm of the track, whereas the second tended to stay around the 3-4dB mark with little movement. Before buying The Glue I hadn’t used a hardware compressor (nor plugin) which had a needle to show the amount of gain reduction… but I’ve found it’s a really useful supplement to know what the compressor is doing, and understand whether it’s imparting the effect you want.

The final link in the chain is the T-RackS Stealth Limiter, and for Cantana 2, I used the following settings…

bus-compression-3-4

This was quite a lot of limiting, and to be honest more than I would like to use, but necessary to be competitive with other tracks in the same style. The nice thing was that the progressive application of compression through the whole effect chain meant that I could use such aggressive settings in the Stealth Limiter whilst still maintaining reasonable clarity and transparency.

I find that applying compression like this to the master bus can sometimes cause a loss of high end, and in the case of Cantana 2 I used an EQ with a very slight high shelf boost to compensate for this (placed before the Stealth Limiter)…

bus-compression-3-5

Anticipating the Effects of Compression

I touched on this briefly in my last post… obviously introducing compression (and especially significant amounts of compression) is going to alter the level balance of different elements in a track… and I’ve found it can be beneficial to anticipate these changes and compensate for them in your original mix accordingly. The case I discussed in the last post related to reverb… reducing the dynamic range of the sound brings the level of quieter parts (like reverb effects) closer to the main sounds in a track, so in Cantana 2 I dropped the level of the overall reverb sends by a couple of dB in the original mix, and then re-rendered it for bus compression. I did a similar thing for some of the low-level background/atmospheric incidental and percussive sounds in the track too… without dropping the level to compensate for the compression, the final compressed mix turned out a bit ‘muddier’ than the original. Another useful tip is to render small, key parts of the original track (rather than the entire track) when auditioning these level changes. I’m using a fairly old PC, so the mix project (with stacks of plugins and including multiple CPU-intensive reverbs) only renders in slightly better than realtime… it’s much more efficient to try dropping the levels of the quiet parts by a certain amount, and then just rendering short clips of the key sections of the track. These short clips can then be imported into the bus compression project, and the changes auditioned without having to wait for the entire track to render.

Results

The net result of this new approach is I’m able get more competitive levels, and still maintain a more clean/transparent mix than before. It again reiterates my belief in a progressive/layered approach to compression that I discussed in my first bus compression post. The less work a compressor has to do, the more easily and transparently it can do it, so using multiple, staged applications of compression for different specific purposes seems to make sense. Following this idea over the last 12 months has also made me have a greater consciousness of compression and evenness of levels during the writing and mixing phases of a track… so my mixdowns prior to bus compression tend to have a lot smoother and more even levels to begin with. You can see this by just visually comparing the pre-bus compression render of an earlier track (The Yellow Room) against Cantana 2…

bus-compression-3-6
‘The Yellow Room’ pre-bus compression waveform
bus-compression-3-7
‘Cantana 2’ pre-bus compression waveform

If you’re writing in a style where competitive levels are important, the more you even out the levels in the early stages of writing and mixing, and the more progressive approach you take to master bus compression, the more easily your final limiter will be able to get to the required competitive level.

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Sidechain Compression on Basslines

The use of sidechain compression on various elements of club tracks is these days fairly well prolific.  Given that fact, you might wonder why I’m posting about sidechain compression of basslines… a fundamental technique, that’s been used in club music for years.  Whilst it’s a well known technique, it’s also not always easy to execute, nor to judge whether you’ve achieved the correct effect. Hence I wanted to document a few notes about my typical approach to sidechaining basslines, and a real example from a recent track.

The first thing to note is that it’s very hard to give ‘ballpark’ settings for bassline sidechain compression. Appropriate settings depend a lot on the tonality of the kick drum, and moreso the pattern of the bassline. If I’m trying  to come up with initial settings for the compressor, I tend to think about it analytically, along the lines of the following. ..

  • Fundamentally, you want to avoid having the bassline and bass drum overlap by playing the same frequency range at the same time.  I aim to set the compressor to compress the bassline where any such overlapping exists.
  • As bass drums typically start with a higher frequency attack (e.g. click) and then quickly descend in pitch to a low drone as they decay, the decay portion is typically where you need to be careful of overlapping the bassline.
  • The attack and release parameters are important as they’ll typically contribute a lot to the feel or groove of the bass. For example if your bassline notes are sounding at the same time as the decay of the kick, you’ll typically want to use a fast attack setting, so the compressor is engaged quickly when the drum and bassline notes overlap. Conversely, if the bass drum and bassline notes are more separated in terms of timing (i.e. little overlap), a slower attack setting might provide a more natural sound.
  • Depending on how quickly a bass drum hit sounds after a preceding bassline note will similarly contribute to the release setting.  As with the attack setting, generally the greater the overlap of notes in this regard, the quicker release setting you might want to use.
  • EQ filtering of the sidechain input from the bass drum can sometimes be useful to prevent certain frequency ranges from triggering the compressor.  E.g. if the pitch of your bassline is relatively high compared to the drum,  you may want to apply some high pass filter to the sidechain input,  so that the low frequency parts of the bass drum don’t trigger the compressor (if the bassline is relatively higher pitched, there should be less overlap at the lower frequencies)

That said, I usually use the above thinking as a guide only, and ultimately the sound and feel/groove should determine the final settings.  This is a case where it’s highly preferable to use monitors with a sufficient low frequency response, so you can really hear (and/or feel) the effect of the sidechained compression.

For my track ‘Cantana 1‘, I used the following settings…

sidechain-compression-on-basslines-1

The controls which don’t have marked scales were set as follows…
Sidechain HP: 29Hz
Threshold: -12.6dB

The bassline in this track was very much a ‘drone’ type sound, rather than having clearly separated, distinct notes.  Because of this, there was not much (if any) natural gap between the bass drum hits and the bassline notes.  Hence I lent towards fast attack and fast release settings to try and maximize the separation between the two parts (i.e. avoid the aforementioned ‘overlap’ as much as possible).  I started out with a fairly fast release setting also to try and make the initial attack of the bass drum more isolated, and more prominent.  The threshold and ratio were set by ear… I just kept adjusting both until I achieved what I thought gave the best balance between the levels of the bass drum and bassline.  I.e. I wanted to strike a balance between…

  • Not having too much compression so that the bassline level was pushed down too far with each drum hit.
  • Not having too little so that the two sounds were too smeared and indistinct.

The final attack and release settings were also set by just auditioning various combinations and deciding which gave the best rhythm and feel (after starting with the dials on the faster end of the scale, as mentioned).

Before and after audio clips of the 2 parts soloed are below (again you’ll need headphones or monitors with adequate bass response to properly hear the difference)…

Without sidechain compression

With sidechain compression

Although the audible difference is fairly subtle, the bassline’s waveform changes considerably…

sidechain-compression-on-basslines-2
Normal bassline waveform
sidechain-compression-on-basslines-3
Bassline waveform with sidechain compression

Bus Compression 2

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

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.