Electrical Model for Free Air



Calculate Res - Lces - Cmes for the electrical speaker model


Closed Box Vented Box

More Info About Loudspeaker Electrical Model's

The speaker equivalent circuit is the actual core of the theories crafted by Thiele and Small.
Every component of a speaker can be “transformed” into an electrical component, to form a circuit that acts exactly the same as the speaker (electrically).

Now imagine that you get different resistors, inductors and capacitors, and arrange them in such a way, that when you measure the impedance of this newly formed circuit, it’s exactly the same as the impedance of the speaker. A similar thing happens when you place the speaker in a box. Additional components are added to the circuit. That is how Thiele and Small manage to predict the behavior of enclosures.

  • Re = DC resistance of a loudspeaker transducer, measured in ohms.
  • Le = Voice coil inductance measured in millihenries (mH) (measured at 1 kHz).
  • fs = is the free-air resonant frequency of a speaker
  • Bl = The product of magnet field strength in the voice coil gap and the length of wire in the magnetic field, in tesla-metres (T·m).
  • Mms = Mass of the diaphragm/coil, including acoustic load, in grams. Mass of the diaphragm/coil alone is known as Mmd
  • Cms = Compliance of the driver's suspension, in metres per newton (the reciprocal of its 'stiffness').
  • Rms = The mechanical resistance of a driver's suspension (i.e., 'lossiness') in N·s/m


  • Cmes = Cone Suspension
  • Lces = Cone mass
  • Res = Cone Losses



Parameter Input


Voice Coil DC Resistance, Re [Ω] =
Voice Coil Inductance, Le [mH] =
Resonance Frequency, Fs [Hz] =
Motor Force Factor, Bl [Tm] =
Moving Mass, Mms [g] =
Compliance, Cms [mm/N] =
Mechanical Resistance, Rms [kg/s] =



Plot Impedance Curve



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