| A | Attenuation, loss of db |
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| B | Magnetic flux density in gap |
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| Bl | Electro-magnetic force factor |
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| BL | Driver motor strength |
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| c | Propagation velocity of sound at STP, approx. 342 m/s |
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| Cab | Acoustic compliance of air in the enclosure |
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| Cas | Acoustical equivalent of Cms |
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| Cmes | The electrical capacitive equivalent of Mms |
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| Cms | The driver's mechanical compliance (reciprocal of stiffness) |
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| D | Effective diameter of driver |
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| F3 | -3 dB cutoff frequency |
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| Fb | Enclosure resonance (usually for reflex systems) |
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| Fc | System resonance (usually for sealed box systems) |
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| Fs | Driver free air resonance. This is the point at which driver impedance is maximum |
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| l | Length of wire immersed in magnetic field |
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| Lces | The electrical inductive equivalent of Cms |
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| Le | Driver inductance (voice coil, mainly) |
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| Levc | Driver voice coil inductance |
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| Mas | Acoustical equivalent of Mms |
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| Mms | The driver's effective mechanical mass (including air load) |
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| n0 | The reference efficiency of the system |
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| p | Density of air at STP 1.18 kg/m^3 (rho) |
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| Pa | Acoustical power |
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| Pe | Electrical power |
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| Q | Ratio of reactance to resistance (series circuit), or resistance to reactance (parallel circuit) |
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| Qa | The system's Q at Fb, due to absorption losses |
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| Qec | The system's Q at resonance (Fc), due to electrical losses |
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| Qes | The driver's Q at resonance (Fs), due to electrical losses |
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| Ql | The system's Q at Fb, due to leakage losses |
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| Qmc | The system's Q at resonance (Fc), due to mechanical losses |
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| Qms | The driver's Q at resonance (Fs), due to mechanical losses |
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| Qp | The system's Q at Fb, due to port losses (turbulence, viscosity, etc.) |
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| Qtc | The system's Q at resonance (Fc), due to all losses |
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| Qts | The driver's Q at resonance (Fs), due to all losses |
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| Ras | Acoustical equivalent of Rms |
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| Re | Driver DC resistance (voice coil, mainly) |
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| Revc | DC resistance of the voice coil only |
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| Res | The electrical resistive equivalent of Rms |
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| Rg | Amplifier source resistance (includes leads, crossover, etc.) |
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| Rms | The driver's mechanical losses |
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| SAF | Spouse Acceptance Factor |
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| Sd | Effective piston radiating (surface) area of driver |
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| Vab | The volume of air having the same acoustic compliance as the enclosures |
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| Vas | The volume of air having the same acoustic compliance as the driver suspension: Cms |
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| Vb | Net internal volume of enclosure |
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| Vd | Maximum linear volume of displacement of the driver (product of Sd times Xmax) |
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| Xmax | Maximum peak linear excursion of driver |
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| Z | Total driver impedance |
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