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Posted

I know how to get port area in square inches, but how do I find out the port length and tuned frequency? I need to know the math to aquire my goals. cant find anything on this specifically, only port area which i already know

Solving For Length of Vent or Port

subwoofer_vent_port_equation_length_l.png

Note

k values:

vent has one free end and one flanged = 0.732

vent has two free ends = 0.614

vent has two flanged ends = 0.850

Where

Lv = length of port or vent

Dv = diameter of port or vent

Dmin = minimum diameter of port or vent

Np = number of ports or vents

Vb = volume of box

fb or Fb = tuning frequency

k = end correction factor

Sd = surface area of subwoofer

Vd = driver displacement volume

Xmax = maximum linear displacement of driver

Important to note that "flanged" and "flared" are not even remotely the same. Flanged means that the end of the port is flush with a flat surface like an outside face of the box, whereas a free end is just the port sticking out into space like the open end of a PVC port inside a box withnothing around it. Flared means that there is a flare (like the bell on a trumpet) on one or both ends of the port. There are equations for that as well and they are somewhere in this forum. I built a fairly simple Excel spreadsheet for flared port calcs that DevilDriver hosted somewhere. Again there should be a link in that thread.

Important to note that "flanged" and "flared" are not even remotely the same. Flanged means that the end of the port is flush with a flat surface like an outside face of the box, whereas a free end is just the port sticking out into space like the open end of a PVC port inside a box withnothing around it. Flared means that there is a flare (like the bell on a trumpet) on one or both ends of the port. There are equations for that as well and they are somewhere in this forum. I built a fairly simple Excel spreadsheet for flared port calcs that DevilDriver hosted somewhere. Again there should be a link in that thread.

IF you find that link please post it, I can add it to my bookmarks.

Important to note that "flanged" and "flared" are not even remotely the same. Flanged means that the end of the port is flush with a flat surface like an outside face of the box, whereas a free end is just the port sticking out into space like the open end of a PVC port inside a box withnothing around it. Flared means that there is a flare (like the bell on a trumpet) on one or both ends of the port. There are equations for that as well and they are somewhere in this forum. I built a fairly simple Excel spreadsheet for flared port calcs that DevilDriver hosted somewhere. Again there should be a link in that thread.

IF you find that link please post it, I can add it to my bookmarks.

http://www.soundground.ca/index/flared_port_calc.xls

there it is... :rockwoot:

:boobs2:

  • 3 weeks later...
  • 2 months later...

So if Dv = the diameter of the port or vent, how would you measure this given a square port? Sorry if this additional question is redundant.

convert from a rectangle port to a circle port with equivalent area

Thank you sir! I think I have got it. :D

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