You might check out the North Creek Music website. www.northcreekmusic.com
Here is an exerpt from the Rhythm speaker building manual courtesy of North Creek's Web Site:
2) Cut the straws into 5" lengths. Insert the straws into the end of the tube with one inch sticking out.
The fit should be so tight that the straws begin to go out of round (65 straws for a 2" port, 125 straws for a
3" port).
3) Wrap the straw bunch sticking out of the port tube with tape. This secures the straws and makes it
easy to adjust the length emerging from the port.
One can adjust the length of straws emerging from the port to adjust the tuning frequency by ear. We
have found the optimum to be between 1" and 2½".
Once the "perfect" tuning is reached, the port can be fixed by dipping the entire assembly in clear shellac
or black paint.
For those that are curious about the origin of this procedure, to the best of my knowledge it was first
discussed in writing by Neville Theile himself. The earliest reference I know of was in an article by Dr.
Theile in an ASA journal from the mid '60's, on non-linear port behavior. Which article and year it was
precisely is now unknown to me. -GS
The method also involves inserting a straw sized wooden dowel into the mass of taped straws, dipping the taped straws and dowel into shellac and letting it dry for a couple days. You can use the inserted dowel (which should be longer than the straws) to tune your port. The dowel, now glued to the straw mass will move the straw in or out of the port effectively increasing or decreasing the length of the port and its output in hz and db. As the port gets longer the tuning reaches lower frequencies but the output in db's drops.
Have fun.
Here is an exerpt from the Rhythm speaker building manual courtesy of North Creek's Web Site:
2) Cut the straws into 5" lengths. Insert the straws into the end of the tube with one inch sticking out.
The fit should be so tight that the straws begin to go out of round (65 straws for a 2" port, 125 straws for a
3" port).
3) Wrap the straw bunch sticking out of the port tube with tape. This secures the straws and makes it
easy to adjust the length emerging from the port.
One can adjust the length of straws emerging from the port to adjust the tuning frequency by ear. We
have found the optimum to be between 1" and 2½".
Once the "perfect" tuning is reached, the port can be fixed by dipping the entire assembly in clear shellac
or black paint.
For those that are curious about the origin of this procedure, to the best of my knowledge it was first
discussed in writing by Neville Theile himself. The earliest reference I know of was in an article by Dr.
Theile in an ASA journal from the mid '60's, on non-linear port behavior. Which article and year it was
precisely is now unknown to me. -GS
The method also involves inserting a straw sized wooden dowel into the mass of taped straws, dipping the taped straws and dowel into shellac and letting it dry for a couple days. You can use the inserted dowel (which should be longer than the straws) to tune your port. The dowel, now glued to the straw mass will move the straw in or out of the port effectively increasing or decreasing the length of the port and its output in hz and db. As the port gets longer the tuning reaches lower frequencies but the output in db's drops.
Have fun.