port length

[busterno1]

I am putting a large port [ 76mm X 503mm] in a small box . because it has a bend in it.

It is hard to get the length right how far out can i be on the length a couple of mm or more which is better longer or shorter ? what effect will this have on the box ? Thanks

[Volenti]

A longer port will give a lower tuning frequency, a shorter one give a higher tuning frequency.

On a port that long a couple of cm either way won't make any difference.

[MITMechE]

I'm just shooting from the hip on this one for the most part, so take that for what it's worth...

Adding an elbow in tube flow increases the head loss. Which should make sense to you intuitively. So, if there's an option of being over or under, with an elbow, I'd go for under because the elbow should actually decrease the tuning freq of the port, so the decrease in length should compensate somewhat.

[Circlotron]

Don't forget the port volume subtracts from the box volume.

[kelticwizard]

Buster:

A couple of mm either way on a 503mm, (20 in), port will have virtually no effect on the tuning. In a 60 liter box, a change of a couple of mm will not even amount to 0.1 Hz.

[VEC7OR]

You can try a slot port - where one of its sides is the wall of the box - fairly easy to fold inside, or if amount of moved air isnt big enough stick with 5cm port.