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Tuesday, March 28, 2017
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   Onken Bass Enclosure

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.

    Onken speaker calculator

Based on research of M.Eijiro Koizumi, J.Mahul & J.Hira

Driver Parameters

all fields are required!

Fs [Hz] Free air resonant frequency of the driver
Re [ohms] dc resistance of the driver
Qms [Hz] mechanical Q of the driver
Qes [Hz] electrical Q of the driver
Mms [gr] total cone assambly mass of the driver
Sd [cm2] effective radiation area of the driver
Rg [ohms] total components resistance (xover-coiol, terminal, wires, etc.)
Port width [cm] indicate the width of one port
Port height [cm] indicate the height of one port
Quantity [ ] number of ports used (Onken speakers have 6 or 8 identical ports)
n [ ] Alignment (best alignment = 5.7, Onken alignmet = 6.34)  *

* Note: you can play with the aligement factor ( n ) to maintain the Portlenght ( L ) under 30 cm

             if the Portlength is over 35 cm, your driver is not suitable for the Onken speker application!

    Onken speaker calculations

Qts: calculated total Q of driver at fs Cms: calculated driver suspension compliance
Vas: calculated air volume driver compliance (liters)
F-3: box cutoff frequency at -3dB (Hz) Fb box cutoff frequency (Hz)
Cab acoustical box compliance Map acoustical mass box
no driver reference efficiency (%)
Sport (cm2)   total port area (Sport should be equal
or max. 15% less then Sd)
Port volume total volume occipied by all ports in the box (liters)
Port length effective port length (cm) Port length corrected corrected effective port length (cm)

note: if the corrected effective port length is over 35 cm, your driver is not suitable for the Onken speaker application!
Vb total internal volume of box (liters)
Vb total total internal volume of box plus the required volume for the vent (liters)
SPL total efficiency of the system including Rg (dB 1W/1mtr)