fresh1

iTrader: (2)

So, I was pondering some different ports I have seen other the years, and was wondering if maybe the more knowledgeable guys here can help me out.

Does the shape/number of the port effect the spl and/or sq? For instance, I have a port that is a 30 inch slot port running along my box. Another guy shows up with the same setup and same box in terms of volume but instead of a box size port he has a port maybe 1'x1' and 10 inches long, assuming it tuned the box to the same frequency. Then guy C shows up with the same box but with PSP ports, and guy D shows up with 2 slot ports, and guy E has 8 port tubes.

Are there any advantages to any one type of port(s)? I know for spl purposes it makes tuning someone easier with port tubes because you can adjust on the fly, but beyond that I'm lost.

Lord Huggington

iTrader: (1)

Shouldn't a round port get air out of the box better?

DeadlySones

iTrader: (4)

I think most the difference lays in the ports ability to smooth the transition between the air moving with velocity inside the port to the standing air outside of it. That is one thing that makes "flares" so useful. They aid in that transition.

Dukk

Assuming that the vent area remains the same:

- A single vent is better than multiples
- A round port is better than a rectangular vent
- The farther from square a rectangular vent is, the less efficient it is. Try to avoid anything over 6:1
- Bends lower efficiency. If you must bend a vent, make it as smooth and gradual as possible.
- Flares add efficiency

fresh1

iTrader: (2)

I thought flares had a positive effect as well. Why are squared rectangluar ports better? The bends I understand, though I would also like to know what makes a round vent superior to a rectangular one, if you don't mind me asking Dukk.

Dukk

For a given area, a circle has less perimeter than a square. For example a 4" round port has about 13% less perimeter than a square vent of the same area and less than HALF the perimeter of a 1" x 12.57" rectangular vent.

The air in the vent drags along the wall of the vent so the more wall (perimeter) the less efficiency.

Also, the air in the corners of a rectangular vent doesn't move very well, reducing the effective area of the vent by about 4% on average.