| Parameter |
Measure |
| 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 |
| 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 |
| nO |
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 |
| High Q |
Any rating over .55, usually better for high powered applications |
| Low Q |
Any rating below .55, usually better without an enclosure in low powered applications |
| Qa |
The system's Q at Fb, due to absorption losses; dimensionless |
| Qec |
The system's Q at resonance (Fc), due to electrical losses; dimensionlessThe 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 / Re |
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 |
| SPL/ 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 meters |
| Xmag |
(DUMAX) -Excursion limit due to the magnetic limitations of the driver's motor. Xmag is defined as the displacement at which the BL product has fallen to 70% of its value at the cone's rest position. |
| Xsus |
(DUMAX) - Excursion limit due to the driver's suspension. Xsus is defined as the point at which the compliance of the suspension has decreased to 25% of the value at the cone's rest position. |
