# Sealed or Closed Subwoofer Box Design Calculator

## Car Audio - Home Theater Sound System

AJ Sealed Designer calculates the required sealed/closed enclosure parameters for woofers and subwoofers.

Subwoofer Box Comparison Calculator:
Compare bandpass, sealed and vented frequency output graphs for a subwoofer in one program.

#### Equations:

 if if

Where

 Inputs Vas = air volume equal equal to compliance of driver suspension Qts = total driver Q at fs fs = driver resonance frequency Qtc = total system Q at fc Calculated Vb = net enclosure volume(internal) f3 = frequency where the 3 decibel power drop occurs fb = box resonance frequency dbpeak = system response maximum dip or peak

#### Input Parameters:

Notes:
• Theile Small parameters are required for input. These values can be found in the speaker's manual or on the manufacture's web site.
• For Qtc, choose a value between 0.1 and 2.0. A value between 0.5 and 1.2 gives the best results. Try varying this parameter to see how the size of the box and the frequency response can be changed.
 Theile/Small Parameters Vas liters Qts unitless fs Hz User Defined Parameter Qtc unitless

#### Calculated Values:

Notes:
• f3 is the most meaningful parameter. The lower the f3 parameter the deeper the bass will sound. An f3 below 50 Hz is suitable for a sealed enclosure. An value below of 40 hz gives the best results.
• Vb is the net size (volume) of the enclosure to be built. Generally, the lower the bass the larger the box.
• In the frequency response plot, the output SPL, sound pressure level, is based at 1 watt/meter.

 Vb = 58.3698 liters f3 = 49.6266 Hz fb = 49.1228 Hz dbpeak = 0.00180918 db

#### References:

• Dickason, Vance. 1991. The Loudspeaker Design Cookbook. Audio Amateur Press. 4th ed.
• Steele, Brian. 2002. The Subwoofer DIY Page v1.1. http://www.diysubwoofers.org.

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By Jimmy Raymond

Contact: aj@ajdesigner.com