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   Bass reflex box after the Onken principle


Building a 15-inch Jensen / Onken Bass Reflex Loudspeaker

  • In order to achieve an optimal quality (Qtc=0.707), the so-called Thiele Aligement (n) is used - usually n=5.7

  • The total area of the tunnels is about 90% of the total area of the active diaphragm surface in the best case.

  • Moved air masses behind the driver and in the tunnels should be identical.

  • The resistance of the low-pass inductor is to be included absolutely also into the computation of the total quality factor (Qts)!

  • To the housing volume (Vb) the tunnel volume has to be added.



Necessary data :

Fs [Hz] Free air resonant frequency of the chassis
Qts [ ] Total quality factor of the chassis
Vas [l] Equivalence volume of the chassis in Ltr.
R [cm] Diaphragm radius
n [ ] Thiele - Alignement


Fs [Hz] : Qts : Vas [ltr] :  


R [cm] : Aligement (n) :  




Vb [liters] Net volume of the box
Fc [Hz] -3dB Frequency
Fb [Hz] Resonant frequency box
Tm [cm2] Port area
L [cm] Port length
Pvb [liters] Port volume
Vb (liters) : Fc (Hz, -3 dB) : Fb (Hz) :
Vb (incl. Pvb) : liters  
Tm (cm2) : L (cm) : Pvb (liters) :