Enter the speed of sound in air, the volume of the speaker box, the density of air, and the cross-sectional area of the port into the calculator to determine the tuning frequency of the bass reflex speaker. This calculator can also evaluate any of the variables given the others are known.

Bass Reflex Formula

The following formula is used to calculate the frequency of a bass reflex speaker.

Fb = v / (2 * π * √(Vb * ρ / A))

Variables:

  • Fb is the tuning frequency of the bass reflex speaker v is the speed of sound in air (approximately 343 m/s) π is a mathematical constant whose value is approximately 3.14159 Vb is the volume of the speaker box ρ is the density of air (approximately 1.2 kg/m³) A is the cross-sectional area of the port

To calculate the tuning frequency of a bass reflex speaker, divide the speed of sound in air by the product of 2, π, and the square root of the quotient of the volume of the speaker box and the product of the density of air and the cross-sectional area of the port.

What is a Bass Reflex?

A Bass Reflex is a type of speaker system design that uses a port or vent cut into the speaker cabinet, leading to an internal resonance chamber. This design enhances the speaker’s efficiency at low frequencies, allowing it to produce deeper bass sounds than a similar speaker in a sealed enclosure. The port redirects sound from the rear of the speaker cone and combines it with the sound from the front, reinforcing lower frequency response and improving the overall sound quality.

How to Calculate Bass Reflex?

The following steps outline how to calculate the tuning frequency (Fb) of a Bass Reflex speaker using the given formula:


  1. First, determine the speed of sound in air (v). This value is approximately 343 m/s.
  2. Next, determine the volume of the speaker box (Vb).
  3. Next, determine the density of air (ρ). This value is approximately 1.2 kg/m³.
  4. Next, determine the cross-sectional area of the port (A).
  5. Next, substitute the values of v, π, Vb, ρ, and A into the formula: Fb = v / (2 * π * √(Vb * ρ / A)).
  6. Finally, calculate the tuning frequency (Fb) using the formula.
  7. After inserting the variables and calculating the result, check your answer with a calculator.

Example Problem:

Use the following variables as an example problem to test your knowledge:

Speed of sound in air (v) = 343 m/s

Volume of the speaker box (Vb) = 0.5 m³

Density of air (ρ) = 1.2 kg/m³

Cross-sectional area of the port (A) = 0.02 m²