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Loudspeaker Diffraction Loss and Baffle Step Compensation


Loudspeaker Diffraction Loss and Baffle Step Compensation Circuit

At high frequencies, a loudspeaker radiates sound directly forward in half space. At low frequencies, the sound is not direectional and radiates into full space. This results in a gradual shift in the frequency response of -6dB from the highs to the lows. This loss of bass can be modeled and compensated for. For more technical information on the subject see these great pages, Loudspeaker Diffraction Loss and Compensation by John L. Murphy and Baffle Step Compensation by Rod Elliott. The calulator below can be used to calculate a passive baffle step compensation circuit.


Speaker Baffle Step Compensation Cicuit Calculator

A Baffle Step Correction Circuit (also referred to as Baffle Step Compensation or Baffle Difraction Loss), can be used to solve the baffle step response problem of loudspeakers in free space. A schematic of the Baffle Step Correction Circuit is shown below. The Baffle Step Correction Circuit is placed between the amplifier and the speaker. For information and theory and examples of a passive baffle step compensation circuit, see Martin J. King's article Simple Sizing of the Components in a Baffle Step Correction Circuit.

Speaker Baffle Step Correction Circuit / Compensation (BSC) Schematic

Figure 1: Speaker Baffle Step Correction (BSC) Circuit Schematic

Where:

  • Re is the DC resistance of the driver voice coil [ohms],
  • Wb is the width of the baffle [inches],
  • dB is the amount of attenuation required [decibels],
  • f3 is the frequency midpoint of the transition from 4π space to 2π space,
  • Lbsc is the calculated baffle step correction circuit Inductor [mH] and
  • Rbsc is the calculated baffle step correction circuit Resistor [ohms].

You can use this online calculator to determine the value of the required baffle step correction circuit Inductor (Lbsc) and Resistor (Rbsc). To use the online calculator, simply enter Re, Wb and dB (the amount of attenuation required) into the boxes below and click the CALCULATE button. Use the CLEAR button to reset all the values.

NOTE: This online calculator requires that JavaScript be enabled on your browser.

Re [ohms]
Wb [inches]
dB [decibels]
f3    [Hz]
Lbsc [mH]
Rbsc [ohms]

Speaker Baffle Step Compensation Cicuit Calculator


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