The K-System

This page is not intended to fully explain the K-System and it’s backgrounds, but just the basics. For more indepth information, please read this article about level practices written by mr. Katz.

The K-System defines three metering scales, with different headroom. The systems are: K12, K14 and K20. The number defines the available headroom for the set. All measurements are in dBr, in contrast to standard VU or RMS meters. As the name says, it’s really a system. Every set depends on a calibrated monitor setting. For example, the K20 set has the standard 83dB monitor level at 0dBr, that’s –20dBFS. The K14 has 83dB at –14dBFS and so on. The main advantage is that you always work at the same monitor level, and the chosen set defines how much headroom there is available.

Typical uses for the three systems are:

  • K20: wide dynamic music / classical / “audiophile”
  • K14: high fidelity music for home listening, rock, folk, pop etc
  • K12: broadcast productions

Monitor calibration

Besides metering the Sonoris meter allows for accurate monitor calibration. By calibrating your monitors to a fixed level synchronized to a scale, the Sonoris Meter becomes a powerful tool allowing you to make more consistent masters with regard to loudness.

Calibration is simple, first select what channel to use for the calibrated pink noise (bandlimited 20Hz-20KHz or 500Hz-2KHz), L, R or both. The levels are calibrated to show 0dBr on any K-scale or -20dBr on the regular scale. You can calibrate your monitors at this level to show 83dB on a slow, C-weighted SPL meter using your monitor control. In stereo mode add 3dB. Mark the monitor control levels for each scale and you are done!

The 500Hz-2KHz noise signal can give a better and more stable reading on the SPL meter under some circumstances. Please try both options and see what works best for you.

RMS and Leq loudness measurement

RMS. This is the standard non-weighted implementation of RMS. Regardless of the samplerate, the bandwidth is 20 Hz to 20KHz (-0.1dB). The RMS calculation window is 1024 samples and metering ballistics are 600 msec. attack and release, as defined in the K-System specification. The 0dBr level is calibrated with –20dBFS pink noise.

Leq(A). This is the first implementation of a K-System meter with Leq. The definition of Leq is: “The level of a constant sound, which in a given time period has the same energy as a time-varying sound”. Leq is also used in loudness meters for measuring aircraft noise or industrial noise over a long period. In the Katz proposal the Leq is measured over a 3 sec. interval. This is implemented in the plugin. The (A) stands for A-weighting filter. This filter approximates the loudness sensitivity of the human ear. In practice, you see a nice and rather slow meter, that translates the loudness very well.

Correlation metering

At the bottom of the meter you see a correlation meter that consists of a row of leds that range from -1 to +1. This meter shows the correlation between the signals of the left and right channels. 

  • If the signals are in phase, the meter shows “1”.
  • If the signals are out of phase, the meter shows “-1”.
  • If the signals are completely uncorrelated, the meter shows “0”.

For normal stereo recordings, the meter should indicate a value between “0” and “1”. When one of the signals is absent, the meter shows “0”, because this is the neutral position. Negative values for a longer time indicate possible phase problems.