Speaker Box Calculator
Calculate the optimal enclosure volume for a speaker driver. Determine box size for sealed or ported enclosures.
From driver specifications
Equivalent air compliance
How to Use This Calculator
- Enter the driver diameter in inches (found in driver specifications).
- Enter Qts (Total Q) from driver specifications (typically 0.3-1.0).
- Enter Vas (Equivalent Air Compliance) in liters from driver specifications.
- Select box type (Sealed or Ported).
- The calculator displays the optimal box volume in liters, cubic feet, and cubic inches.
Box Volume Formula
Box volume is calculated from Thiele-Small parameters:
Ported Box: Vb = Vas / ((Qts / 0.4)² - 1)
Where Vb = box volume, Vas = equivalent air compliance, Qts = total Q. These formulas target specific box Q values (0.7 for sealed, 0.4 for ported) for optimal response. Example: Driver with Qts=0.5, Vas=50L in sealed box: Vb = 50 / ((0.5/0.7)² - 1) ≈ 30.6 liters.
Full Description
Speaker enclosure design is crucial for optimal sound quality. The box volume, along with driver parameters, determines the bass response, efficiency, and overall sound character. Too small a box creates boomy, uncontrolled bass. Too large a box reduces efficiency and can cause driver damage. Proper box design requires understanding Thiele-Small parameters.
Thiele-Small parameters describe a driver\'s electrical and mechanical characteristics. Qts (Total Q) describes damping—lower Qts means better damping, suitable for ported boxes. Higher Qts means less damping, suitable for sealed boxes. Vas (Equivalent Air Compliance) describes how much air has the same "springiness" as the driver\'s suspension—larger Vas means the driver needs a larger box.
This calculator helps you determine the optimal box volume based on driver parameters. Enter Qts, Vas, and choose sealed or ported, and it calculates the recommended volume. Use it when designing speaker enclosures, selecting drivers, or understanding how box size affects sound. Remember that actual box design requires additional considerations like port tuning (for ported boxes), internal bracing, and room acoustics.
Frequently Asked Questions
What is Qts?
Qts (Total Q) is a driver parameter that describes the damping and resonance characteristics. It combines electrical Q (Qes) and mechanical Q (Qms). Lower Qts (<0.5) works better in ported boxes, higher Qts (>0.7) works better in sealed boxes. Qts around 0.5-0.7 works in both.
What is Vas?
Vas (Equivalent Air Compliance) is the volume of air that has the same compliance (springiness) as the driver's suspension. It's measured in liters or cubic feet. Larger Vas means the driver needs a larger box. Vas is found in driver specifications.
What's the difference between sealed and ported enclosures?
Sealed (acoustic suspension) enclosures provide tight, accurate bass but less output. Ported (bass reflex) enclosures provide more bass output and efficiency but can be less accurate. Ported boxes are larger and require tuning. The choice depends on your priorities and driver characteristics.
How accurate are these calculations?
These are simplified calculations based on Thiele-Small parameters. Actual box design requires more factors: driver Fs (resonant frequency), box Q, port tuning (for ported), and room acoustics. Use this as a starting point, then fine-tune based on measurements and listening.