I do not know if you had used ChatGPBT on engineering and IT. I had been using it on software coding recently, which is saving me a lot of time and effort. I thought how about a question on speaker design.

The first one is a pretty straightforward calculation of a driver's suitability to the a job.

My driver has the following TS parameters: fs = 22 Hz , Qts = 0.38 and VAS = 119L. What will be the enclosure volumes in litres and f3 frequency of a B2 aligned closed box and a B4 aligned vented box? On the vented box I use a pipe with a 7.5cm diameter. What will be the fB frequency and the pipe length required for the B4 alignment?

For a B2 aligned closed box, the enclosure volume can be calculated as follows:

Qtc = 0.707

Qtc = (Vb * 1.84 * fs^2) / (c^2 * Vas)

where Vb is the enclosure volume in cubic meters, fs is the driver's resonant frequency in Hz, c is the speed of sound in m/s, and Vas is the driver's equivalent volume in liters.

Solving for Vb:

Vb = (Qtc * c^2 * Vas) / (1.84 * fs^2)

Vb = (0.707 * (343)^2 * 119) / (1.84 * (22)^2) ≈ 46.5 L

For a B4 aligned vented box, the enclosure volumes can be calculated as follows:

Qtc = 0.707

Qtc = (Vb * 1.06 * fs^2) / (c^2 * Vas * fB^2)

where Vb is the enclosure volume in cubic meters, fs is the driver's resonant frequency in Hz, c is the speed of sound in m/s, Vas is the driver's equivalent volume in liters, and fB is the box tuning frequency in Hz.

Solving for Vb:

Vb = (Qtc * c^2 * Vas * fB^2) / (1.06 * fs^2)

Vb = (0.707 * (343)^2 * 119 * (20)^2) / (1.06 * (22)^2) ≈ 236.3 L

To calculate the box tuning frequency f3 for the vented box, we can use the following formula:

f3 = (0.84 * fs) / (2 * pi * sqrt(Qts))

f3 = (0.84 * 22) / (2 * pi * sqrt(0.38)) ≈ 25.8 Hz

To calculate the required port length for the B4 alignment with a 7.5cm diameter pipe, we can use the following formula:

fB = (c / (2 * pi * sqrt(Vas * Vb))) * ((D / 2)^2 / L)

where c is the speed of sound in m/s, Vas and Vb are the driver's equivalent volume and enclosure volume respectively in cubic meters, D is the diameter of the port in meters, and L is the length of the port in meters.

Converting the port diameter to meters:

D = 7.5 / 100 = 0.075 m

Solving for L:

L = (c / (2 * pi * sqrt(Vas * Vb * fB))) * ((D / 2)^2)

L = (343 / (2 * pi * sqrt(119 * 0.2363 * 20))) * ((0.075 / 2)^2) ≈ 0.27 m or 10.6 inches.

Therefore, the enclosure volume for the B2 alignment is 46.5 L, the enclosure volume for the B4 alignment is 236.3 L, the f3 frequency for the vented box is approximately 25.8 Hz, the port tuning frequency fB is 20 Hz, and the required port length for the B4 alignment with a 7.5cm diameter pipe is approximately 0.27 m or 10.6 inches.

I then asked a reverse calculation; what type of driver I need for my choice of a box.

What will be the approximate range of TS parameters for a driver to have f3=20Hz on a 200L vented box and what will be the port length for a 3" pipe?

To design a vented enclosure with a tuning frequency of 20 Hz and a volume of 200 liters, you can use the following steps:

The first one is a pretty straightforward calculation of a driver's suitability to the a job.

**Question to ChatGPT**:My driver has the following TS parameters: fs = 22 Hz , Qts = 0.38 and VAS = 119L. What will be the enclosure volumes in litres and f3 frequency of a B2 aligned closed box and a B4 aligned vented box? On the vented box I use a pipe with a 7.5cm diameter. What will be the fB frequency and the pipe length required for the B4 alignment?

**Answer from ChatGPT**:For a B2 aligned closed box, the enclosure volume can be calculated as follows:

Qtc = 0.707

Qtc = (Vb * 1.84 * fs^2) / (c^2 * Vas)

where Vb is the enclosure volume in cubic meters, fs is the driver's resonant frequency in Hz, c is the speed of sound in m/s, and Vas is the driver's equivalent volume in liters.

Solving for Vb:

Vb = (Qtc * c^2 * Vas) / (1.84 * fs^2)

Vb = (0.707 * (343)^2 * 119) / (1.84 * (22)^2) ≈ 46.5 L

For a B4 aligned vented box, the enclosure volumes can be calculated as follows:

Qtc = 0.707

Qtc = (Vb * 1.06 * fs^2) / (c^2 * Vas * fB^2)

where Vb is the enclosure volume in cubic meters, fs is the driver's resonant frequency in Hz, c is the speed of sound in m/s, Vas is the driver's equivalent volume in liters, and fB is the box tuning frequency in Hz.

Solving for Vb:

Vb = (Qtc * c^2 * Vas * fB^2) / (1.06 * fs^2)

Vb = (0.707 * (343)^2 * 119 * (20)^2) / (1.06 * (22)^2) ≈ 236.3 L

To calculate the box tuning frequency f3 for the vented box, we can use the following formula:

f3 = (0.84 * fs) / (2 * pi * sqrt(Qts))

f3 = (0.84 * 22) / (2 * pi * sqrt(0.38)) ≈ 25.8 Hz

To calculate the required port length for the B4 alignment with a 7.5cm diameter pipe, we can use the following formula:

fB = (c / (2 * pi * sqrt(Vas * Vb))) * ((D / 2)^2 / L)

where c is the speed of sound in m/s, Vas and Vb are the driver's equivalent volume and enclosure volume respectively in cubic meters, D is the diameter of the port in meters, and L is the length of the port in meters.

Converting the port diameter to meters:

D = 7.5 / 100 = 0.075 m

Solving for L:

L = (c / (2 * pi * sqrt(Vas * Vb * fB))) * ((D / 2)^2)

L = (343 / (2 * pi * sqrt(119 * 0.2363 * 20))) * ((0.075 / 2)^2) ≈ 0.27 m or 10.6 inches.

Therefore, the enclosure volume for the B2 alignment is 46.5 L, the enclosure volume for the B4 alignment is 236.3 L, the f3 frequency for the vented box is approximately 25.8 Hz, the port tuning frequency fB is 20 Hz, and the required port length for the B4 alignment with a 7.5cm diameter pipe is approximately 0.27 m or 10.6 inches.

I then asked a reverse calculation; what type of driver I need for my choice of a box.

**Question to ChatGPT**:What will be the approximate range of TS parameters for a driver to have f3=20Hz on a 200L vented box and what will be the port length for a 3" pipe?

**Answer from ChatGPT**:To design a vented enclosure with a tuning frequency of 20 Hz and a volume of 200 liters, you can use the following steps:

- Calculate the volume of the vented section:

- The vented section volume can be calculated using the following formula: Vv = Vb * ((fb / f3)^2 - 1) where Vb is the box volume, fb is the port tuning frequency, and f3 is the -3dB frequency cutoff of the system.
- For this design, Vb = 200 liters, fb = 20 Hz, and f3 = 20 Hz, so: Vv = 200 * ((20 / 20)^2 - 1) = 0 liters (rounded to 1 liter)

- Determine the TS parameters:

- To achieve a low-frequency response with a tuning frequency of 20 Hz, the driver should have a low fs (resonant frequency) and a high Vas (equivalent compliance volume), while maintaining a low Qts (total Q factor) to allow for a smooth rolloff and better control of the cone motion.
- The range of TS parameters for such a driver can vary depending on the specific design and other factors, but a typical range may be:
- fs: 15-25 Hz
- Vas: 150-250 liters
- Qts: 0.3-0.5

- Calculate the port length:

- The length of the port can be calculated using the following formula: L = (c / (2 * pi * D)) * ((fb / f3)^2 - 1)^(-1/2) where c is the speed of sound, D is the diameter of the port, fb is the port tuning frequency, and f3 is the -3dB frequency cutoff of the system.
- For a 3-inch (7.62 cm) diameter pipe, D = 7.62 cm / 2 = 3.81 cm.
- Assuming a speed of sound of 343 m/s, the length of the port for this design is: L = (343 / (2 * pi * 3.81)) * ((20 / 20)^2 - 1)^(-1/2) = 10.4 cm

Last edited: