How do you modify standard port calculations to account for a folded slot port such as this:
http://www.diyaudio.com/forums/showthread.php?postid=1139936#post1139936
The cross-sectional area and the centerline distance are pretty straightforward. What effect will the "folding" of the port have, and how will putting the port inlet flush with the cabinet wall affect tuning?
Nice design by the way, ckwase. I like the proportions, and want to do something similar. Do you have a project thread for it?
http://www.diyaudio.com/forums/showthread.php?postid=1139936#post1139936
The cross-sectional area and the centerline distance are pretty straightforward. What effect will the "folding" of the port have, and how will putting the port inlet flush with the cabinet wall affect tuning?
Nice design by the way, ckwase. I like the proportions, and want to do something similar. Do you have a project thread for it?
You measure the length along the centreline of the port. Model it as a round port of equivalent cross-sectional area.
Where the port shares one wall of the box, the port appears longer. According to JL Audio , the effective length is the physical length plus half the height. I'm not sure what the correction is when the port shares three walls.
Also see this thread at AVSForum.
Depending on how low you can get your port speed, turbulence may be an issue. This can be minimised by routing flares on the intake and exit of the port. You can also use split PVC let into the corners to provide a smoother turn.
Where the port shares one wall of the box, the port appears longer. According to JL Audio , the effective length is the physical length plus half the height. I'm not sure what the correction is when the port shares three walls.
Also see this thread at AVSForum.
Depending on how low you can get your port speed, turbulence may be an issue. This can be minimised by routing flares on the intake and exit of the port. You can also use split PVC let into the corners to provide a smoother turn.
Collo, thanks for the links. I have a bass guitar box I've started and will finish when I get some time that has a need for a longish port to get the SBB4 tuning I want. Using the PVC as roundovers inside was something that had completely bypassed me and is an elegant solution.
Lots of very useful info and data on your site. I've enjoyed reading it.
Lots of very useful info and data on your site. I've enjoyed reading it.
Here is a calculator for a single bend slot port.....
http://reaudio.com/speaker_box/LPort_Box_Calc.html
I'm not sure if it calculates end correction or not.
http://reaudio.com/speaker_box/LPort_Box_Calc.html
I'm not sure if it calculates end correction or not.
Awesome resources. Thanks! I hadn't considered smoothing the bend with PVC. My bends will be quite a bit tighter, but maybe I can figure something out.
In WinISD, I'm toying around with a design using a Tang Band W8-1363 in 0.5 cubic feet tuned to 32 Hz. To get the port speed below the "whistle" level with a 100W signal, it's telling me I need a port about 48 inches long, with a port resonance of ~143 Hz. This will be very near the crossover from satellites to sub. Sounds like a bad idea to this subwoofer newbie. Am I right? Are there practical work-arounds, maybe a notch filter?
In WinISD, I'm toying around with a design using a Tang Band W8-1363 in 0.5 cubic feet tuned to 32 Hz. To get the port speed below the "whistle" level with a 100W signal, it's telling me I need a port about 48 inches long, with a port resonance of ~143 Hz. This will be very near the crossover from satellites to sub. Sounds like a bad idea to this subwoofer newbie. Am I right? Are there practical work-arounds, maybe a notch filter?
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