Sixth-Order Bandpass Subwoofer Enclosure Design Calculator

Explanation of Terms
Qts, Vas, and Fs, are the electro-mechanical parameters for your woofer. They are also commonly referred to as the "Thiele-Small" parameters. You can get these from the paperwork that came with your speakers, from the dealer where you purchased your speakers, or from the manufacturer of the speaker (they are sometimes hard to contact, however).
F3(L) - the frequency where the response is down by 3 dB (on the low end of the passband). This will be the first number in the "Passband" box when you calculate an enclosure.
F3(H) - the frequency where the response is down by 3 dB (on the high end of the passband). This will be the second number in the "Passband" box when you calculate an enclosure.
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). This is usually referred to in speaker design with other terms, which serve to make it a valid reference point.

A typical specification for a bandpass enclosure would be :

Efficiency/Sensitivity : 94 dB @ 1W/1M.

 This means that this design is capable of creating a sound pressure level of 94 dB when a signal of 1 watt is applied to it, and is measured with the measuring instrument 1 meter (approximately 3.28 feet) away from the speaker system.

Bandpass Subwoofer Enclosure Image

Typical Sixth-Order Bandpass
Enclosure Design  
 This style of enclosure is patented by the Bose Corporation, information provided is for personal use only.
Calculate Your Enclosure Here
 One of the reasons bandpass enclosures are so popular is because of an inherent property they have that allows the enclosure designer the flexibility to trade bandwidth for efficiency and vice versa. This calculator will design a 6th order bandpass enclosure. This calculator is only for Qts values from 0.18 to 0.28.
 To use this calculator, enter your values for Qts, Vas, and Fs, and then click the "Calculate Enclosure" button. Your results will appear in the other boxes.

Note : Too much gain can be hazardous to your speakers, try to keep it +3 dB or less unless you want to find out what your speakers look like with holes in them.
Number of Drivers 
Isobaric Loading
Yes  No
  
Enter Qts Enter Vas  (ft3 )Enter Fs 
Vf = (ft3 )
Vr =  (ft3 )		 Fb(F) = Hertz
Fb(R) =  Hertz		 Passband =  Hertz
Gain = (dB SPL@1W/1M)

  If you want to experiment with different quantities of drivers, or the isobaric option, you don't need to enter all of the values again, just change the value you want to adjust and click the "Calculate Enclosure" button again. When you are finished, write down your enclosure specifications, (or copy & paste them), and go here to design the port(s) for your new subwoofer enclosure.

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