Sixth-Order Bandpass Subwoofer Enclosure

Explanation of Terms
Qts, Vas, and Fs, are the electro-mechanical parameters for your woofer. ("Thiele-Small" parameters)
F3(l) - the frequency where the response is down by 3 dB (on the low end of the passband).
F3(h) - the frequency where the response is down by 3 dB (on the high end of the passband).
Vf - the internal volume of the front chamber of the enclosure.
Vr - the internal volume of the rear chamber of the enclosure.
Fb(f) - the frequency that the vent in the front chamber of the enclosure needs to be tuned to.
Fb(r) - the frequency that the vent in the rear chamber of the enclosure needs to be tuned to.
Passband - refers to the range of frequencies that will be allowed to pass through the speaker system (the frequencies you will be able to hear/feel). Any frequencies above or below the passband will be attenuated (reduced).
Gain - the amount of boost(or in some designs the amount of attenuation) in sound pressure level(SPL).
Bandpass Subwoofer Enclosure Image
Typical Sixth-Order Bandpass Enclosure.

The isobaric loading method involves the pairing of two woofers into a tightly coupled “iso-pair”. Typically the iso-pair are configured in a cone-to-cone or cone-to-magnet push-pull configuration, with a common body of enclosed air adjoining one side of each diaphragm. The woofers work as if a single unit, with the direct radiation from the front woofer combining with the output of the companion rear woofer in a tuned vented enclosure.
Isobaric Box Types

The net result of isobaric loading is that the coupled pair produce the same frequency response in half the box volume that a single speaker of the same type would require.
Isobaric loading can be used within almost any enclosure type, including sealed, vented or bandpass configurations.

Calculate Your Enclosure

 This calculator will design a 6th order bandpass enclosure. This calculator is only for Qts values from 0.18 to 0.36
 Note : Too much gain can be hazardous to your speakers, try to keep it +3 dB or less.

Number of Drivers :
Isobaric Loading : Yes    No  
Qts : Vas :  [Ltr] Fs :
Vf =  [Ltr] Vr =  [Ltr]
Fb(F) =  [Hz] Fb(R) =  [Hz]
Passband =  [Hz]
Gain =  [dB]

Calculate Vent Length for front- or rear chamber

Vent Diameter:  [cm]
Tuning Frequency (Fb(f) or Fb(r)):  [Hz]
Enclosure Volume (Vf or Vr):  [Ltr]
Number of vents: 

Vent length = 

Vent Area:  (you can change this to recalculate Vent Diameter & Length) [cm2]

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