D

Damping Factor (DF)
Ratio of speaker impedance to amplifier output impedance. High DF (>100) means tight bass control. Formula: DF = Zspeaker / Zoutput. Wire resistance reduces system DF significantly. → See also: Output Impedance
Chapter 6.1

dB (Decibel)
Logarithmic unit for sound pressure level, power, voltage. +3 dB = double power. +10 dB = 10× power. +20 dB = 100× power. SPL: 85 dB comfortable, 100 dB loud, 120 dB threshold of pain, 140 dB+ causes hearing damage. → See also: SPL
Chapter 1.1

dB Drag Racing
SPL competition organization. Measures peak sound pressure level at specific test frequency (typically 40, 50, or 63 Hz) using TermLab meter positioned at A-pillar. World record: 180+ dB. → See also: SPL, IASCA
Chapter 13.1

Dirac Live
Automated room correction algorithm. Measures multiple positions, generates FIR correction filters to flatten response and reduce reflections. Available on select DSPs (miniDSP C-DSP 8×12 DL). → See also: FIR, Room Correction
Chapter 12.6

DMM (Digital Multimeter)
Electronic testing tool measuring voltage, current, resistance. Essential for setting amplifier gain (measure output voltage at rated power). True RMS models required for AC measurements. → See also: Gain Setting, RMS
Chapter 4.4

DSP (Digital Signal Processor)
Device applying digital processing: crossovers, EQ, time alignment, level control. Sits between source and amplifiers. Professional systems use standalone DSP. Entry-level: miniDSP 2×4 HD ($100). Pro: Helix DSP Pro ($900). → See also: Active Crossover, Time Alignment
Chapter 12

DVC (Dual Voice Coil)
Subwoofer with two voice coils on same former. Allows flexible impedance wiring. DVC 4Ω wired parallel = 2Ω, series = 8Ω. Common for matching amplifier impedance ratings. → See also: Impedance, Voice Coil
Chapter 10.1