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Twisting a port? (1 Viewer)

Adam O

Stunt Coordinator
Joined
Jul 22, 1999
Messages
91
I was just curious if you needed a 30" port in your sonotube-based sub, but your tube was around 25" in height, could you use pvc plubing pipe and put together several pieces with u-curves in them to achieve this length? or would the curves in the port effect the sound??

Sorta Like This:

|---------------

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| _____ /

| / _ I I

| I I I I I I

| I I I I_I I

| I I _____/

|-/ -----------

Thanks Alot

Adam
 

Dustin B

Senior HTF Member
Joined
Mar 10, 2001
Messages
3,126
It's been done.
Link Removed
But I've never seen a definative answer as to whether it affects the sound or not.
 

Richard Greene

Stunt Coordinator
Joined
Mar 5, 2001
Messages
148
To Pat:

That picture looks like Reason #14 for using

passive radiators rather than ports.

I give you credit for having the courage to post it.

Looks like it would take two days of using differential equations to calculate the volume and length of

THAT port.

Hopefully you won't take this post too seriously.
 

NickSo

Senior HTF Member
Joined
Jul 2, 2000
Messages
4,260
Real Name
Nick So
I have 2 small question regarding port tubes...

Does it make any difference if the lenght of the port is INSIDE the enclosure or not?

And also, would having 2 ports that are say, 10" long each be the same as having 1 port thats 20" long? or at least move the air more efficiently?

Just 2 smallq uestions, hope i haven't hijacked your thread
 

Dustin B

Senior HTF Member
Joined
Mar 10, 2001
Messages
3,126
For question one, no it doesn't matter.

For question two no. There are three things that need to be considered in order to tune an enclosure to a particular frequency. What the net volume of the enclosure is, what the diameter of the port is, and how long the port is.

As examples, assume the other two variables are kept the same.

If you make the enclosure larger, the tuning goes down, make it smaller the tuning goes up.

If you make the port wider, the tuning goes up, if you make the port narrower the tuning goes down.

If you make the port longer the tuning goes down, if you make the port shorter the tuning goes up.

Having two ports is like having a single larger port. But you can't just sum the surface areas of the ports though. The best way I've heard of to figure out what two ports will tune to, is to split the box in half and calculate with one port.
 

Patrick Sun

Senior HTF Member
Joined
Jun 30, 1999
Messages
39,408
Nope, you can have the port on the outside of the enclosure.
Richard, I was just playing around with an old enclosure and that's what happened! :)
 

Marc Bodin

Grip
Joined
Apr 8, 2002
Messages
19
There is no problem with putting bends in a port, as long as you know the total length and area of the port.
 

Rudy H

Stunt Coordinator
Joined
Mar 2, 2002
Messages
105
Putting bends in might actually limit airflow a bit, but not much. I would avoid them if possible though.
 

ThomasW

Senior HTF Member
Joined
Nov 6, 1999
Messages
2,282
In theory ports should be straight. The resistance of the bends are different than that of a straight piece of pipe. It's a little complicated to calculate the resistance of the bends particularly if multiples are involved.

Having said that I don't know if the differences actually translate in to audible performance issues. I've never bothered to make a curved port for a comparison.
 

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