I know some of your ears just perked up with this title..
I'm sure some of you have built your own Sub enclosures over the years, as I have.
In fact, I got my start back in the early 80's when sub enclosures were a fairly new concept to the general public.
I used to pencil out my enclosure dimensions (using the Golden Mean Ratio) enclosure size and port dimensions using the Theil/Small parameters of the driver with a handbook I bought from Radio Shack.
This 'Long Hand' approach usually took me 15-20 minutes to conjure an enclosure.
Now I use WinISDpro modeling software that can do the figures for me, as quickly as I can tap ENTER.
The cool thing about this software, and others as well, is that it models port shape(area) and of coarse, length. AND, as some of you may have noticed, not all port configurations perform/tune equally. Especially if Chuffing is a problem. (20 Hz and below)
SO ! It occurred to me the other day (I have no idea why I didn't think of this earlier..)
Why Not Flow Test Each Port Shape ????
So I did.
Below is a pic of a test sample of 3 equal cross sectional area port shapes.
The area of each port is 1.76 in2 (small, I know but good enough to test the shapes)
First test is just the shape it's self with no flare.. (parameter holes are to bolt it to the flowbench) results below v
Round: 177.8 cfm (parameter area: 4.71 long. Dia x Pi) hole area 1.76
Triangle: 187.7 cfm (parameter area: 7.05 long. .75 x .75 x 2.35 x 2.35) hole area 1.76
Square: 179.6 cfm (parameter area: 5.32 long. 1.33 x 4) hole area 1.76
As you can see, the port shape with the longest parameter area flowed the best. and the rest of the flow numbers are a reflection of the amount of parameter was available to the shape. Interesting, right?
WELL ! lets add some flare, or radii, to the shapes and retest. (1/4" round router bit used)
Results below v
Round: 260.5 cfm (82.5 cfm gain over a non-flared port)
Rectangle: 246.5 cfm (58.8 cfm gain)
Square: 239.4 cfm (59.4 cfm gain)
WHAT ?? just so that you know, I retested EVERYTHING and came up with the same results..
amazing what a little radius can give.
You guys familiar with Areo Ports may not be surprised with this..
The moral of the story here is this; round is a very efficient shape.
It also suggests why the modeling software is sensitive to port configuration.
Thanks for listening !!!
I'm sure some of you have built your own Sub enclosures over the years, as I have.
In fact, I got my start back in the early 80's when sub enclosures were a fairly new concept to the general public.
I used to pencil out my enclosure dimensions (using the Golden Mean Ratio) enclosure size and port dimensions using the Theil/Small parameters of the driver with a handbook I bought from Radio Shack.
This 'Long Hand' approach usually took me 15-20 minutes to conjure an enclosure.
Now I use WinISDpro modeling software that can do the figures for me, as quickly as I can tap ENTER.
The cool thing about this software, and others as well, is that it models port shape(area) and of coarse, length. AND, as some of you may have noticed, not all port configurations perform/tune equally. Especially if Chuffing is a problem. (20 Hz and below)
SO ! It occurred to me the other day (I have no idea why I didn't think of this earlier..)
Why Not Flow Test Each Port Shape ????
So I did.
Below is a pic of a test sample of 3 equal cross sectional area port shapes.
The area of each port is 1.76 in2 (small, I know but good enough to test the shapes)
First test is just the shape it's self with no flare.. (parameter holes are to bolt it to the flowbench) results below v
Round: 177.8 cfm (parameter area: 4.71 long. Dia x Pi) hole area 1.76
Triangle: 187.7 cfm (parameter area: 7.05 long. .75 x .75 x 2.35 x 2.35) hole area 1.76
Square: 179.6 cfm (parameter area: 5.32 long. 1.33 x 4) hole area 1.76
As you can see, the port shape with the longest parameter area flowed the best. and the rest of the flow numbers are a reflection of the amount of parameter was available to the shape. Interesting, right?
WELL ! lets add some flare, or radii, to the shapes and retest. (1/4" round router bit used)
Results below v
Round: 260.5 cfm (82.5 cfm gain over a non-flared port)
Rectangle: 246.5 cfm (58.8 cfm gain)
Square: 239.4 cfm (59.4 cfm gain)
WHAT ?? just so that you know, I retested EVERYTHING and came up with the same results..
amazing what a little radius can give.
You guys familiar with Areo Ports may not be surprised with this..
The moral of the story here is this; round is a very efficient shape.
It also suggests why the modeling software is sensitive to port configuration.
Thanks for listening !!!
