Port Placement Question

[lcolbur1]

Does the placement of a port matter? Ie, right behind/next to the drivers vs. lower/further away from the drivers?

[JonMarsh]

Well, what actually matters the most is the location of the mouth of the port INSIDE the enclosure. Though the placement of the port externally can make a difference, too- for example, it's generally agreed that rear facing ports are not a bad thing, because they tend to minimize putting the midrange port resonance out front, while the impact on the bass from the port is quite minimal.

The internal location is important, because within the enclosure you kind of have two different regions- a high velocity, lower pressure area in the center of the enclosure, and a high pressure low velocity area on the walls. Running a port from one enclosure wall (where it exits) smack over to nearly the other enclosure wall will not get good coupling to the rear wave of the woofer. It will couple better if it's possible for the port entry to be somewhere nearer the center of the box. Naturally, this is tough to do for many enclosure shapes, and for many tunings. In those cases, it's may be a better idea to consider a PR configuration- which has it's own challenges, for sure...

[lcolbur1]

Awesome, thanks. Second question, suppose I have a 6 inch long port and a cabinet with 3 inch walls. I want the port to be flush with the outside wall, which means that 3 inches of the port will be embedded in the wall and the other 3 inches will be in the actual volume of the cabinet. Is this the same as if I had 1 inch walls and 5 inches of the port was enclosed in the cabinet? Can both configurations achieve the same effect in terms of tuning frequency?

[---k---]

Yes. For the most part, the only thing that matters is the length inside the pipe.
Your next question should be about port flares. Are you considering using a flare kit or round over on the port exit? Unibox will model the port flare and give you the correct length with the flare and show you the difference in port air speed.

[lcolbur1]

I finished a design for Zaph's ZRT 2.0's. They'll be curved like my last 2 builds. I'm not incorporating a flared tube and using this site as a guide:

http://www.psp-inc.com/tools.html

I'm starting the build in November and will be posting the process, so stay tuned. :T