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Ok, here is a crazy idea for a twist on the old Sonotube, Drawing attached (1 Viewer)

Mike Keith

Second Unit
Jan 24, 2002
I’m in the process of having a 8”round (top) cone shaped Spire or Finial made by a local wood turner. This would serve as a valve that sits on top (center) of the port of the Maelstrom subwoofers I’m making.

The idea is to have this Finial or Valve be adjustable so that In the open position it hovers about 4” above the port and the cone shape will direct the air from the port out and around it, kinda like how some speakers have down firing ports with this similar device centered in the middle of the port as a pedestal (polk comes to mind) to direct the air flow and help control cuffing.

The difference in this design is that some all-thread steel rod will suspend it, and when screwed in it will close of the port off completely.

The Sonotube volume I have prototyped works well with either vented or sealed, although at a rather low Q in the sealed position (.5), anyway, the point is it should dress up this ugly thing a bit (solid Red Oak) and serve as a shelf to put things on.

Maybe I’ll be able to hear the enclosure go aperiodic just as the port is almost closed, should be fun to experiment with anyway.

And critiques, or other ideas?

Please fire away, and here is a link to the AutoCAD 3-D drawing, it’s the engine valve thingy on top.

Wire Frame DWG

Rendered DWG


Senior HTF Member
Nov 6, 1999
Your idea is a variant on so called the Polk power port. They work, but require a bunch of calculations to design and a ton of work to build

HERE's a link to download the Polk power port design info.

Mike Keith

Second Unit
Jan 24, 2002
Useing the info Thomas supplied I should allow the valve to be open a max of 4" for a 8" dia port. I can just put different PVC pipes over the all-thread to change the diameter of the stem as per the Polk spreadsheet.

I cant wait to play with this to see what effect this will have not to mention it will make a great shelf on top of the port.

I’m also working on Oak inlays for the top 27” diameter disk that will be in a circular pattern to match my main speakers, this should make this a very unique and adjustable sonotube.

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