Ever wondered what all those spec's that come with your subs mean ? Here's a glossary of what they stand for, what they measure and how. Sub specs AKA T/S specs AKA T/S Parameters.. T/S = Thiele-Small (the dudes who invented them).

Theile-Small Parameters  Glossary.

B: Magnetic flux density in gap, in Tesla-meters (TM)

BL: The magnetic strength of the motor structure.

C: Propagation velocity of sound at STP, approx. 342 m/s

Cas: Acoustical equivalent of Cms

Cmes: The electrical capacitive equivalent of Mms, in farads

Cms: The driver's mechanical compliance (reciprocal of stiffness), in m/N

D: Effective diameter of driver, in meters

F3: -3 dB cutoff frequency, in Hz

Fb: Enclosure resonance (usually for bass reflex systems), in Hz

Fc: System resonance (usually for sealed box systems), in Hz

Fs: Driver free air resonance, in Hz. This is the point at which driver impedance is maximum.

L: length of wire immersed in magnetic field, in meters

Lces: The electrical inductive equivalent of Cms, in henries

L: Length of wire immersed in magnetic field, in meters

Ms: The total moving mass of the loudspeaker cone.

Mmd: Diaphram mass, in grams

Mms: The driver's effective mechanical mass (including air load), in kg

n0: The reference efficiency of the system (eta sub 0) dimensionless, usually expressed as %

p: (rho) Density of air at STP 1.18 kg/m^3

Pa: Acoustical power

Pe: Electrical power

Q: The relative damping of a loudspeaker

Qa: The system's Q at Fb, due to absorption losses; dimensionless

Qec: The system's Q at resonance (Fc), due to electrical losses; dimensionless

Qes: The driver's Q at resonance (Fs), due to electrical losses; dimensionless

Ql: The system's Q at Fb, due to leakage losses; dimensionless

Qmc: The system's Q at resonance (Fc), due to mechanical losses; dimensionless

Qms: The driver's Q at resonance (Fs), due to mechanical losses; dimensionless

Qp: The system's Q at Fb, due to port losses (turbulence, viscousity, etc.); dimensionless

Qtc: The system's Q at resonance (Fc), due to all losses; dimensionless

Qts: The driver's Q at resonance (Fs), due to all losses; dimensionless

R: Ripple, in dB

Ras: Acoustical equivalent of Rms

Res: The electrical resistive equivalent of Rms, in ohms

Revc: DC voice coil resistance, in ohms

Rg: Amplifier source resistance (includes leads, crossover, etc.), in ohms

Rms: The driver's mechanical losses, in kg/s

Sd: Effective piston radiating area of driver, in square meters

SPLo: Sound Pressure Level, usually measured at 1 watt, at 1 meter in front of the loudspeaker

Vas: "Equivalent volume of compliance", this is a volume of air whose compliance is the same as a driver's acoustical compliance Cms (q.v.), in cubic meters

Vd: Maximum linear volume of displacement of the driver (product of Sd times Xmax), in cubic meters.

Xmax: Maximum peak linear excursion of driver, in centimeters.