Has anyone tried the "power port" design from Polk audio

[bigsausagepizza]

Polk has been using this technology for a long time, it is supposed to allow you to dramatically shrink the length and diameter of your ports without introducing port noise. Last week polk had a cool page on it at their "polk university" site, but that is now unavailable.

Here's the thread from Home Theater Shack where I found this: http://www.hometheatershack.com/forums/diy-subwoofers-general-discussion/16591-power-port-calculations.html

There is a link on the page to download a spreadsheet with all the calculations. It seems like a legitimate design for getting low tuning with reasonably sized ports. Here's the diagrams from the spreadsheet:

I'm thinking about using this to build a small home theater sub with tuning in the 15-20hz region.

[philrab]

So, it's a traditional flare port with an insert/airguide?

On the doublesided port, how exactly would you affix the center guide? Just seams like it's hanging in the air.

[TRON]

All that port does is allow you to increase the port opening size without changing the tuning. I don't really see what you would gain with that other than less port noise. I also don't think you'll get lower response just becasue of the port. You want low, build a horn or quarter wave.

At the end of the day, it's still just a ported enclosure.

[bigsausagepizza]

All that port does is allow you to increase the port opening size without changing the tuning. I don't really see what you would gain with that other than less port noise. I also don't think you'll get lower response just becasue of the port. You want low, build a horn or quarter wave.

At the end of the day, it's still just a ported enclosure.

Have you checked out the spreadsheet? It seems to be the actual spreadsheet polk uses ("Confidential Property of Polk Audio, Inc"), and they put this into some of their highest end speakers. If you play with the spreadsheet it shows you can use dramatically shorter and smaller ports and achieve the same tuning. For example, if I plug in a standard 3" diameter 40" long port, it says I can use a 2" diameter port, 11" long, with 8" disks on each end ( w/ 3" diameter flow guide cones and 1/2" roundover on the port tube).

If this is correct (Polk has patents on it and use it in their high end equipment, so I want to trust them), using a ~12" long port seems pretty great compared to using a 40" port. Here's a build that used this design, he was able to use a 36.5" long port instead of a 62.5" long port, and the tuning came in exactly as predicted (11hz!!!, those HT guys are nuts). http://www.hometheatershack.com/forums/home-audio-subwoofers/10524-custom-re-xxx-subwoofer-build.html