D

Damping Factor (DF)
Ratio of loudspeaker impedance to amplifier output impedance. Higher damping factor usually means lower source impedance and better electrical control of the driver, but cable resistance reduces the effective system damping factor quickly. See also: output impedance, loudspeaker impedance.
Chapter 6.1

dB (Decibel)
A logarithmic ratio, not a standalone unit. A dB value must always reference something: power, voltage, sound pressure, digital full scale, or another baseline. See also: dBFS, dBu, dBV, SPL.
Chapter 1.1

dBFS
Digital level relative to full scale. House rule: if a document is otherwise ambiguous, assume 0 dBFS means full-scale sine RMS and report sample-peak and true-peak separately when they matter. See also: true peak, RMS, headroom.
Chapter 12

dBu
Analog voltage level referenced to 0.775 Vrms. Common in professional audio signal chains and preferred when describing analog line levels in DSP and amplifier interfaces. See also: dBV, Vrms, gain structure.
Chapter 6.2

dBV
Analog voltage level referenced to 1.0 Vrms. Common in consumer gear; -10 dBV is a typical consumer nominal line level and does not equal +4 dBu. See also: dBu, Vrms.
Chapter 6.2

Dither
Low-level noise added intentionally when reducing bit depth so quantization behaves more linearly. Dither removes correlated truncation distortion; noise-shaping can then move that noise spectrally. See also: noise shaping, bit depth.
Chapter 12.7

Dynamic Range
The usable span between the noise floor and the upper limit defined by clipping or a stated measurement criterion. It is not the same metric as SNR and should always be reported with bandwidth, weighting, and method. See also: SNR, THD+N, measurement standard.
Chapter 12.8

Dirac Live
Automated room-correction system that measures multiple listening positions and generates correction filters. Useful as an example of FIR-based correction, but the measurement, target curve, and verification workflow still matter more than the brand name. See also: FIR, room correction.
Chapter 12.6

DMM (Digital Multimeter)
Electronic test tool for voltage, current, resistance, and continuity checks. A true-RMS meter is preferred when using AC voltage to verify amplifier gain or line-output behavior. See also: RMS, amplifier gain.
Chapter 4.4

DSP (Digital Signal Processor)
Hardware or software that applies digital operations such as crossovers, EQ, delay, routing, limiting, and analysis. In practice the DSP layer is where terminology drift around dB references, filter naming, latency, and metering causes the most confusion. See also: headroom, Q, Linkwitz-Riley, LUFS.
Chapter 12

DVC (Dual Voice Coil)
Subwoofer motor structure with two coils on the same former, allowing multiple wiring impedance options. Useful electrically, but it does not change the acoustic alignment math by itself. See also: impedance, voice coil.
Chapter 10.1

Related reference: Audio Levels, Metering, and Headroom.