3 How Limitless works and a guide to Limiting
The Threshold control on a limiter is really an input gain. Limiting at the threshold and then turning the gain up is the same as turning the gain up and then limiting at 0dBFS.
The simplest limiter adds gain and clips. It wouldn’t be much of a limiter, but it would make things louder. A more sophisticated limiter will work out how much gain is reduced when clipping and release it gently. More sophisticated still is the technique of delaying the audio (lookahead), to allow a gentle attack time. There’s a problem with having one release time though, which is that either you set the release time short, so that it recovers quickly after a peak, and suffer it sounding aggressive on loud sustained material, or you set it long and have dips in level after every transient. In general, a compromise here is a bad compromise.
One solution to this problem is to automatically adapt the release time to the duration of the transient. This improves matters, but it depends on how well the algorithm adapts to your specific material. A better solution, and one that many engineers adopt, is to use a pair of limiters - one to control the dynamics, and another to catch the peaks. This is the strategy that Limitless adopts, but in an integrated way - the dynamics limiter allows transients to pass, configurably, letting the second stage catch the peaks.
Limitless also goes further, with a linear phase crossover of up to 6 bands. By separating out the bands we can prevent the scenario where one loud frequency drags down everything else. Multiband limiters have a reputation for sounding aggressive, when in fact they can achieve much greater transparency (as Limitless will demonstrate). The bad rap appears to be a consequence of the release time issue described above.
To a mathematician, limiting is a delightfully well specified problem. The peaks reach but do not exceed 0dBFS. Given another constraint, it’s possible to formulate the problem in such a way that a numerical solver can be built to achieve certain criteria. In Limitless, the operating principle is that the most transparent limiting is a fixed gain reduction - so we strive for maximal smoothness of the gain reduction signals. With the constraints of peak limiting and maximal smoothness, we designed a numerical solver, which per-sample solves to find the gentlest possible adjustments that will prevent clipping.
So here’s Limitless. It can be louder than other limiters without audible distortion, but that’s not the point. Using Limitless you can achieve pop loudness without losing your dynamics. More importantly, Limitless is designed around modern loudness standards, so it’s easy to target a specific Loudness - full metering and history is built in.
Another trick a lot of top-flight engineers use is clipping the signal before the limiter, to reduce the work the limiter has to do to peaks. Limitless features a full-spec clipper with massive oversampling, so you can achieve the “clipped convertor” effect inside the box. And at the output is a simple but thoroughly modern dither.
