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Discussion Starter #1 (Edited)
I had been looking into these things for years but I never got very far until recently, when I stumbled accross a design for a power port that was designed to tune a 300L+ enclosure to 10Hz. Very soon after I found the calculator on another forum.

The idea behind these things is fairly straightforward. The picture you are about to see is effectively a cross section through the length of the port & you'll notice that the air exits at the sides rather than straight out of the end. This has the same radiating area as a much larger port but is a of a lot smaller, as far as I'm aware the port geometry also inhibits the ports natural resonance which can be a pain in a conventional reflex port. In other words it doesn't act like an organ pipe as a conventional port would due to it's length.

I'd love to have drawn my own picture, but credit must go to whoever actually did this one (apologies as I honestly cannot remember where I found this :rolleyesno:). Kudos to whoever did though as I eventually came up trumps - thank you!



As you can see the port tube is quite a bit smaller in diameter than the original 8.72" port, so the air velocity inside is a lot higher. At each end it slows as it is expanding round the flow guides & at the exit of the port (on the sides) it has the same area as the original 8.72" standard port. Except now it's considerably shorter & much easier to fit into an enclosure :T

Here is what the spreadsheet calculation for that particular port looked like.



Effectively you need to work out a suitable conventional port with low enough air velocity so that the spreadsheet can calculate the power port from it's air mass. You'll want to have the equivalent mouth area of the standard port or greater to keep air velocity out of the port as low as your design requires.

You'll need Excel or Spreadsheet from Microsoft Works or similar to use the calculator.

View attachment pwrport.zip

Unzip & off you go...


E2A:- I really should add that this is a patented technology & while there should be no problem in using it for private use, it cannot be used commecially. Polk Audio own the patents.
 

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Discussion Starter #4
Thanks for posting this here Mark!
You are most welcome :T As I have learn't in the past it's best to spread things around, as if you lose them you have a much higher chance of getting them back again than if you didn't :D So while it is sure to benefit someone, or possibly a good few on here I may well be doing myself a favour down the line...

I know I found it incredibly handy, so I feel pretty sure others will...

Happy new year :)
 

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Thank you for this (I think) but how is the valve-like structure supported inside the port? Have you or anybody here actually built one please?
 
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