Help in determine port dimensions

[shlomid]

Hallo

I want to make sure that I understand accurately the port dimensions from schematics (see pic attached).

The port is PVC plumbing pipe.

What is pipe dimension? 2" (50mm) Inside diameter and 2 3/8 outside diameter?

If I understand right, the pipe wall would be very thick, about 3/16" (0.476mm).

Right now I have PVC with outside diameter of 2" (50mm) and inside of about 1.81" (46mm) wall thickness is 3/32" (2mm)
Can I use it?

Thank you.

 

[00600]

Minimum Port Diameter
To calculate the minimum diameter of the port required to prevent port noises, you will also need to know the following:

Xmax = maximum linear displacement (mm)
Dia = Effective diameter of driver (cm)
Np = number of ports

Calculate the minimum port diameter from the following equations:

Sd = pi*(Dia/100)^2/4
Vd = Sd*Xmax/1000
Dmin = 100*(20.3*(Vd^2/Fb)^0.25)/Np^.5

where,

Dmin = minimum port diameter (cm)

AND

The port length required to tune a volume of air to a specific frequency can be calculated by using the following equation:

Lv = (23562.5*Dv^2*Np/(Fb^2*Vb))-(k*Dv)

where,

Dv = port diameter (cm)
Fb = tuning frequency (Hz)
Vb = net volume (litres)
Lv = length of each port (cm)
Np = number of ports
k = end correction (normally 0.732)

(taken from diysubwoofers.org written by Brian Steele)

 

[Kent Smith]

You could use slightly smaller pipe, but the length will change (shorter). Have fun with math!

 

[shlomid]

thanks

I don’t know the Xmax or the Effective diameter.
But from the later equation and the original tube size I found that the tuning frequency is about 62Hz.
I enter this and the new diameter and found that the length is 11.14cm.

I did not calculate the minimum port diameter, let’s hope that 1.81" will be enough

Thank you.