Q

Q Factor (Quality Factor)
Bandwidth and damping descriptor used in multiple contexts. In EQ, higher Q means a narrower filter; in electromechanical driver parameters, Q describes damping behavior. Good docs state which domain they mean instead of assuming one universal interpretation. See also: bandwidth, Qts, parametric EQ.
Chapter 4.5

Qts (Total Q)
Thiele-Small parameter describing total driver damping around resonance. It is one of the key indicators used in enclosure alignment decisions, but it should be interpreted with Fs, Vas, excursion, and actual design goals rather than used alone. See also: Thiele-Small, enclosure alignment.
Chapter 10.1

Q Versus Bandwidth
Two ways of describing filter sharpness. If a page uses Q, it should say Q; if it uses bandwidth in octaves, it should label octaves explicitly rather than assuming they are interchangeable. See also: parametric EQ, octave bandwidth.
Chapter 12.3

Related reference: Audio Levels, Metering, and Headroom.