Port Length Calculator
Calculate the optimal port length for your subwoofer box design
Calculate Subwoofer Port Length
Total number of ports in the subwoofer box
Internal diameter of each port tube
Internal volume of the subwoofer enclosure
Desired resonant frequency of the port
Port end configuration affects the end correction factor
Fine-tune the end correction factor manually if needed
Port Length Results
Port Area
0.00 cm²
Area per port
Total Port Area
0.00 cm²
Combined area of all ports
Formula used: L = (23562.5 × D² × N) / (V × F²) - (k × D)
Parameters: D=0cm, N=1, V=0L, F=0Hz, k=0.732
Port Length Analysis
Example Calculation
12" Subwoofer Box
Number of ports: 1
Vent diameter: 10 cm
Box volume: 50 L
Tuning frequency: 35 Hz
End correction: 0.732 (one flanged)
Calculation
L = (23562.5 × 10² × 1) / (50 × 35²) - (0.732 × 10)
L = 2,356,250 / 61,250 - 7.32
L = 31.18 cm
Port End Types
Both Ends Flanged
k = 0.850
Port ends are flared or rounded
One End Flanged
k = 0.732
Most common configuration
Both Ends Free
k = 0.614
Sharp or cut tube ends
Design Tips
Lower tuning frequency = longer port
Larger box volume = shorter port
Multiple smaller ports vs one large port
Consider port velocity for loud systems
Understanding Subwoofer Port Length
What is a Subwoofer Port?
A subwoofer port (or vent) is a tube or opening in a speaker enclosure that allows air to move in and out. It works together with the enclosed air volume to create a resonant system that enhances bass response at specific frequencies.
Why Port Length Matters
- •Determines the tuning frequency of the enclosure
- •Affects bass response and efficiency
- •Influences port velocity and potential noise
- •Critical for proper system performance
Port Length Formula
L = (23562.5 × D² × N) / (V × F²) - (k × D)
- L: Port length (cm)
- D: Port diameter (cm)
- N: Number of ports
- V: Box volume (liters)
- F: Tuning frequency (Hz)
- k: End correction factor
Note: Ensure all measurements are in the correct units before calculation