S

Sealed (Acoustic Suspension) Enclosure
Closed box, no port. Air spring loads driver. Characteristics: tight bass, 12 dB/octave rolloff below resonance, safe for driver (no over-excursion below tuning). Smaller box = higher Q = more bass emphasis. → See also: Qtc, Ported
Chapter 10.2

Sensitivity
Speaker output measured in dB at 1 watt, 1 meter (dB/W/m). Typical: 85-90 dB (subwoofers), 88-92 dB (components). Higher sensitivity = louder for same power. +3 dB sensitivity = half power needed. → See also: Efficiency
Chapter 10.1

SPL (Sound Pressure Level)
Loudness measured in decibels. Reference: 0 dB SPL = threshold of hearing. 85 dB = comfortable, 100 dB = loud, 120 dB = pain threshold, 140+ dB = immediate hearing damage. Competition: 150+ dB. → See also: dB, Competition
Chapter 13.1

SQ (Sound Quality)
Competition format judging accuracy of music reproduction. Scored on: imaging, tonal accuracy, noise floor, dynamics, installation. Opposite of SPL (which judges maximum loudness). → See also: IASCA, Imaging
Chapter 13.2

Star Ground
Grounding technique where all components ground to single common point. Eliminates ground loops by preventing current flow between grounds. Essential for noise-free systems. → See also: Ground Loop
Chapter 11.3

Subsonic Filter
High-pass filter below subwoofer passband (typically 20-30 Hz). Protects ported subwoofers from over-excursion below tuning frequency. Slope: 24 dB/octave minimum. Mandatory for ported boxes. → See also: Fb, Ported
Chapter 10.3

SWC (Steering Wheel Controls)
Buttons on steering wheel for audio control. Aftermarket integration requires: interface module (Axxess ASWC, PAC SWI-RC), CAN bus connection or analog resistive network. → See also: CAN Bus
Chapter 5.5