You should perform the initial level setting of a limiter on the hottest section of your track as this is where the project and limiters interactions will be most significant.
Levels to aim for: -14 dB LUFS (momentary) average across a track, a -9 dB LUFS peak is a sensible aim for that -14 average.
Questions to guide your decision-making process: Is the limiter working too hard? Is there a single instrument triggering it, rather than a larger portion of the tracks' instrumentation?
Johnathan has learned from his experience that a well-mastered track will have an 85 – 88 dB SPL level.
Gather a bunch of your favourite mastered tracks and measure the SPL of each. Average them, to end up with a ballpark a figure. This way, every time you come into your studio, you've got a reference point to measure your masters against.
Sometimes it is best to use two limiters rather than one to increase a signal's level as it helps reduce any artefacts by not pushing a single limiter too hard.
Mastering ninja's can determine whether louder is better. Does the mix sound better, or just louder? This is a question to keep front of mind when mastering.
Limiters will primarily interact with the low-frequency transients. The first place you will hear the impact of the limiter is on the kick drum. The second place will be the increase in high-frequency content. If you get an increase of too much high-frequency content, vs not enough low, this can be an indication that the limiter is working too hard.
If you run a 100 Hz sine wave into a limiter, with the threshold reducing the sine wave 0.1dB, you'll notice that a bunch of harmonic overtones become present.
This distortion is the byproduct of using a limiter or any compression circuit with a fast release and is what attributes for the increase in high-frequency energy.
If you then set the release a little longer, the harmonics begin to dissipate:
However, a longer release can often be too slow for high-energy tracks.
Visual meters should be used as a reference or guide to confirm something you're hearing, but always lead with your ears.