Showing posts with label Dynamics. Show all posts
Showing posts with label Dynamics. Show all posts

Sunday, 6 July 2014

Limiting inspiration...

Sometimes the spark of an idea can come from a chance comment, and can tip your mind into thinking about something from a different viewpoint. One of the comments on Maxforlive.com for one of my comb-filter-based audio effects set me thinking, because it warned against using limiting because it could change the sound...

Now changing the sound is what audio effects are all about, and every time that I think there isn't any room for anything even remotely new, then up pops something that you hadn't considered before. So after a run of filter-based audio effects, I now had a nagging suspicion that there must be something that hadn't been explored with limiting (or its cousins, compression and expansion, and the evil twin, noise gating). Which is when a crazy idea popped into my head, and resulted in a series of limiter-based effects that reaches its natural conclusion in SyncLimiter.

It is often said that there is nothing new. So I'm cautious about suggesting that this might be new, so I will caveat this with 'new to me'. I've never seen anything that deliberately mis-uses limiting with LFOs setting the threshold, but then I'm a very conventional user of limiters (as in keeping something with lots of time-varying gain stable, as in a swept comb filter) and so I may well merely be revealing my blinkered knowledge.

So with all that out of the way, I present SyncLimiter, an audio effect that has two independent limiters whose thresholds and compression ratios can be modulated by sample-and-hold captured sine waveforms from two independent synch-able LFOs.


I've chosen the 'mirror' look for the UI, so the left and right hand sets of controls are reflected in the vertical axis. The first control to reach is the 'Limiter' control, which is just a lift from previous projects, and which does a complex mapping of threshold and ratio to give a single control that 'feels' right to me. At zero, there's only a slight effect, whilst at 100 there is maybe just a bit too much effect on the sound, and so the place to start is at a setting of about 50. (This is the default). After that, the 'LFO Depth' controls how much the LFO affects the Limiting, and the overall modulation is shown in the dark grey indicator. The 'S&H Freq' control alters the rate at which the LFO sine waveform is sampled (and held), and so at high frequencies (10 Hz) it has little effect, whilst at lower frequencies it chops the sine wave into a 'stepped' waveform. There's lots of scope for exploration here, with the relative ratios between the four frequencies, resulting in a wide variety of stereo changes to the sound. Some of the changes are subtle, others less so.

SyncLimiter works well on drums and rhythmic material like choppy comping. You may even like the way that it can muddle up pads, but using it on vocals is probably limited in its appeal. And actually, there are no rules - and any that you are given are probably interesting to try breaking. I'd be very interested to see in what ways this is mis-used!

I also apologise here to anyone who is offended by this flagrant exploitation of limiting, and I also have to warn users that there may be clicks present in the output of this effect, despite my best efforts with Max's 'line'. This is a dirty and crude effect - you have been warned!

As usual, SyncLimiter can be found at Maxforlive.com (One of these days I hope to make something different enough to get onto the Ableton 'Friday' blog entries!)

Sunday, 9 February 2014

A Limiting Solution part 3

Once I had created LFO Limiter, it occurred to me that I had missed one additional possibility for flexibility - it processed both stereo channels in the same way. So I duplicated the limiter section and produced the stereo version: LFO S Limiter ( available from MaxForLive.com ).


LFO S Limiter (0v01) is just two LFO Limiters stuck together - everything is duplicated and totally separate. So you really can have completely different settings on each stereo channel - even one limited and the other not. My personal preference is for more subtle differences, with the same 'Limiter' depth amount, but slightly different LFO frequencies. Having two separate channels provides more scope for complex rhythmic and syncopation of source material...

The panel design isn't the prettiest I've done, but I struggled to find a way to have the two channels shown clearly. You can see the same dilemma in many of my devices that have two separate channels - Hairbrush is a good example where I have mirrored the two sides to see how that feels, but it isn't a perfect solution. There seem to be at least three different approaches to a two-channel layout, and I'm not sure which is the best one.


Ableton use the 'Vertical Copy' layout in the 'Analog' synthesizer, and where you have a strong flow across, with two channels and a common 'central area', then it works nicely. But you only get a single row of controls, which tends to make the device wide, which can result in lots of scrolling left and right to get the correct device visible.

The two horizontal layout options are interesting. I am very familiar with the 'Horizontal Copy' from older modular synthesizers, where you just double up on the module, and so the layout automatically copies (unless the module is stereo, of course, and modern modules do seem to use horizontal mirroring sometimes). But I actually prefer the 'Horizontal Mirror' because somehow it emphasizes the two channel-ness, and looks better aesthetically. One thought I did have was to run an experiment where I make two versions and see which one gets the most downloads...
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A Limiting Solution part 2

I tend to stick to the same sort of life-cycle when I am creating audio effects. I start with an idea or a need, then try a few potential solutions, and then refine them until there is a 'best' candidate, which is then developed further. What gets published on MaxForLive.com is almost always tagged as 'Work In Progress' because there's always room for improvement. 'Never finish a song...' is the old studio trick of returning to a recording project a few days after it felt perfect, only to find that there are actually loads of things that can be improved. This principle seems to be broadly applicable: Artists apparently always leave a picture with 'three brush-strokes to go...'

When an effect is finished enough to be usable without needing to be fixed every time, then the programming task fades, and the exploration phase starts. For Comber 0v02, this is where serendipity stepped in. I was seeing what the results of some of the control settings were with the new Limiter function, and I was adjusting the Limiter depth control live, riding it as if it was just another controller. And surprisingly, the result was interesting...

Equalizer / Compressor / Limiter
Equalizer / Compressor / Limiter (Photo credit: HSmade)
I've always treated dynamics controls as 'set and leave' devices - you find the right compression, limiting, gating or expansion, and then leave it. The wide use of gated reverb in the 80s (Phil Collins, Allan Holdsworth: Velvet Darkness (not part of the official discography), David Bowie: Low, Peter Gabriel: III...) was one of those 'wow' moments where an un-natural effect sounded really good. Unfortunately, the over-use of gated reverb, particularly on snares, can become a cliche...

But tweaking the Limiter depth control gave another interesting - and not natural - sound. Some similarities to gated reverb, but because it was mixed up with the comb filtering, it was worthy of further exploration...

So I added an LFO to the Limiter control and stripped out all of the comb filtering, resulting in LFO Limiter 0v01, where the depth of limiting changes over time. And because the Limiter depth control is adjusting multiple parameters inside the limiter library object, the LFO is doing something that would require very nimble finger movements on a conventional set of limiter controls.


Limiter 0v01 has very few controls. The 'Quick/Smooth' time response mode switch is the same as in Comber, and the LFO is my usual free/sync sine wave taken from the MaxForLive examples. Because I'm trying to focus the attention of the user on the sound and not the technicalities, I have deliberately not put any animated display of the limiting process in action. After all, you don't show a representation of the comb filter spectral response in a phaser or flanger... Instead you get my standard 'Modulation slider' display that I tend to use whenever a value is modulated by an LFO - in this case the Limiter is modulated by the LFO Depth control. I much prefer bouncy little dots to the usual Ableton method of animating the modulated control (where the Limiter control rotates back and forth in time with the LFO modulation).
LFO Limiter should be on the MaxForLive.com site soon, and can produce some very unusual rhythmic and syncopated effects, particularly when preceded or followed by some echo.

Using LFO Limiter


The best way to explore it is to start out with the LFO Depth set to zero, and just get familiar with the effect of the Limiter control: zero is no limiting, 100 is pure 'pumping'. A setting of about 30 is a good place to start introducing LFO modulation, and my initial preference was to match the LFO Depth and Limiter settings, so try 30 for the LFO Depth at first. (I did contemplate having a single control that replaced the two, but the 'same setting' for both is not always appropriate for some source material, so I have left them as two separate controls.) After that, just tweak and explore.
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