THIELE / SMALL SPEAKER PARAMETERS
This is a short definition list of the Thiele / Small (T/S) speaker parameters. These are electromechanical parameters that can be used to define how a loudspeaker driver performs. They are named after A. N. Thiele and Richard H. Small who pioneered this line of analysis for loudspeakers.
- D - Effective diameter of driver [m].
- Sd - Effective piston radiating area of driver [m^2].
- Xmax - Maximum peak linear excursion of driver [mm].
- Re - DC resistance of voice coil [ohms].
- Rg - Amplifier source resistance (includes leads, crossover ...) [ohms].
- Le - Inductance of voice coil [H].
- Fs - Driver free air resonance [Hz]. Point at which driver impedance is maximum.
- Fc - System resonance [Hz] (typically for sealed box systems).
- Fb - Enclosure resonance [Hz] (typically for reflex systems).
- F3 - -3 dB cutoff frequency [Hz].
- Vas - 'Equivalent volume of compliance' [L], measure of the free air 'stiffness' of the suspension. It represents the volume of air that has the same stiffness as the driver's suspension when acted on by a piston of the same area (Sd) as the cone. A larger values mean lower stiffness, and generally require larger enclosures.
- Vd - Maximum linear volume of displacement of the driver (Vd = Sd · Xmax) [m^3].
- Qms - Q of driver at resonance (Fs), due to mechanical losses [dimensionless].
- Qes - Q of driver at resonance (Fs), due to electrical losses [dimensionless].
- Qts - Q of driver at resonance (Fs), due to all losses [dimensionless].
- Qmc - Q of system at resonance (Fc), due to mechanical losses [dimensionless].
- Qec - Q of system at resonance (Fc), due to electrical losses [dimensionless].
- Qtc - Q of system at resonance (Fc), due to all losses [dimensionless].
- Ql - Q of system at Fb, due to leakage losses [dimensionless].
- Qa - Q of system at Fb, due to absorption losses [dimensionless].
- Qp - Q of system at Fb, due to port losses (turbulence, viscosity ...) [dimensionless].
- n0 (eta sub zero)- Reference efficiency of the system [dimensionless], usually expressed as a percentage.
- Cms - Mechanical compliance (reciprocal of stiffness) of driver [m/N].
- Mms - Effective mechanical mass (including air load) of driver [mg]
- Rms - Mechanical losses of driver [kg/s]
- Cas - Acoustic equivalent of Cms.
- Mas - Acoustic equivalent of Mms.
- Ras - Acoustic equivalent of Rms.
- Cmes - Electrical capacitive equivalent of Mms [F].
- Lces - Electrical inductive equivalent of Cms [H].
- Res - Electrical resistive equivalent of Rms [ohms].
- B - Magnetic flux density in gap [T].
- l - Length of wire immersed in magnetic field [m].
- Bl - Electro-magnetic force factor [T·m].
- Pa - Music power handling capacity of the driver [w].
- Pe - Thermal power handling capacity of the driver [w].
- c - Propagation velocity of sound [~342 m/s].
- p (rho) - Density of air [~1.18 kg/m^3].