Electrical Model for Vented Enclosure



Calculate Res - Lces - Cmes - Rep - Reb - Lceb - Cmep
for the vented electrical speaker model


Free Air Closed 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 kilograms. 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
  • Vas = The Thiele-Small parameter that measures the overall compliance of a loudspeaker transducer. The Vas is defined as the volume of air that has the same compliance as the driver.
  • Qms =The losses or relative damping (ratio of stored to dissipated energy or ratio of reactive to resistive energy) of a driver at Fs, considering only its mechanical (non-electrical) resistances.
  • Qes = The losses or relative damping (ratio of stored to dissipated energy or ratio of reactive to resistive energy) of a driver at Fs, considering only its electrical (non-mechanical) resistances.
  • Qts = The losses or relative damping (ratio of stored to dissipated energy or ratio of reactive to resistive energy) of a driver, considering both mechanical and electrical resistances.
  • Sd = Projected area of the driver diaphragm, in square metres.


  • Res = Mechanical Damping Speaker
  • Lces = Compliance Speaker
  • Cmes = Moving Mass Speaker

  • Reb = Enclosure Losses
  • Lceb = Compliance Enclosure
  • Cmep = Compliance Port
  • Rep = Port Losses


Parameter Input


Voice Coil DC Resistance, Re [Ω] = Equivalent Stiffness Air Volume, Vas [L] =
Voice Coil Inductance, Le [mH] = Mechanical Quality Factor, Qms =
Resonance Frequency, Fs [Hz] = Electrical Quality Factor, Qes =
Motor Force Factor, Bl [Tm] = Total Quality Factor, Qts =
Moving Mass, Mms [g] = Piston Surface, SD [m^2] =
Compliance, Cms [mm/N] =
Mechanical Resistance, Rms [kg/s] =
Enclosure Volume, Vb [L] =
Vent Length, Lvent [mm] =
Vent Diameter, Dvent [mm] =





Calculations:




Plot Impedance Curve




<<< Back