K-System
Bob Katz's metering scheme that ties the meter's zero point to a calibrated monitoring level, turning headroom into a deliberate choice.
Mastering engineer Bob Katz proposed it in the Journal of the AES in 2000, right in the middle of the loudness war. The meter reads RMS level, but zero sits at −20, −14 or −12 dBFS depending on the scale: K-20 for film and classical, K-14 for most pop, K-12 for broadcast. Everything above zero is headroom for peaks.
The other half of the trick lives in the speakers: monitoring is calibrated so that pink noise at meter zero produces 83 dB SPL per channel. A heavily squashed mix then sounds flatter rather than louder, and the urge to push it evaporates. LUFS and EBU R 128 have since taken over the measuring, but the idea of a fixed listening level has stuck.