- Fs - Driver free air resonance, in Hz. This is the point at which
driver impedance is maximum.
- Fc - System resonance (usually for sealed box systems), in Hz
- Fb - Enclosure resonance (usually for reflex systems), in Hz
- F3 - -3 dB cutoff frequency, in Hz
- 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, Liters or feet
- D - Effective diameter of driver, in meters
- Sd - Effective piston radiating area of driver in square meters
- Xmax - Maximum peak linear excursion of driver, usually in millimeters
- Vd - Maximum linear volume of displacement of the driver (product of Sd
times Xmax), in cubic meters.
- Re - Driver DC resistance (voice coil, mainly), in ohms
- Rg - Amplifier source resistance (includes leads, crossover, etc.), in
ohms
- Qms - The driver's Q at resonance (Fs), due to mechanical losses;
dimensionless
- Qes - The driver's Q at resonance (Fs), due to electrical losses;
dimensionless
- Qts - The driver's Q at resonance (Fs), due to all losses; dimensionless
- Qmc - The system's Q at resonance (Fc), due to mechanical losses;
dimensionless
- Qec - The system's Q at resonance (Fc), due to electrical losses;
dimensionless
- Qtc - The system's Q at resonance (Fc), due to all losses; dimensionless
- Ql - The system's Q at Fb, due to leakage losses; dimensionless
- Qa - The system's Q at Fb, due to absorption losses; dimensionless
- Qp - The system's Q at Fb, due to port losses (turbulence, viscosity,
etc.); dimensionless
- n0 - The reference efficiency of the system (eta sub 0) dimensionless,
usually expressed as a percentage
- Cms - The driver's mechanical compliance (reciprocal of stiffness), in
m/N
- Mms - The driver's effective mechanical mass (including air load), in mg
- Rms - The driver's mechanical losses, in kg/s
- Cas - Acoustical equivalent of Cms
- Mas - Acoustical equivalent of Mms
- Ras - Acoustical equivalent of Rms
- Cmes - The electrical capacitive equivalent of Mms, in farads
- Lces - The electrical inductive equivalent of Cms, in henries
- Res - The electrical resistive equivalent of Rms, in ohms
- B - Magnetic flux density in gap, in Tesla
- l - Length of wire immersed in magnetic field, in meters
- Bl - Electro-magnetic force factor, can be expressed in Tesla-meters or,
preferably, in meters/Newton
- Pa - Acoustical power
- Pe - Electrical power
- c - Propagation velocity of sound at STP, approx. 342 m/s
- p - Density of air at STP 1.18 kg/m^3 (rho)
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