Designing a port on WinISD? Need help!

[xluben 10+ year member]

Air velocity graph shows how fast air mass travels in port. In order to keep chuffing noise low, you should limit the peak velocity at 5% of velocity of sound, or about 17 m/s. Like the cone excursion graph, the desired powerlevel is set also by same watts setting. Note that if air velocity peaks exceeds previously mentioned level.

I just modeled the JL 10W7 in 1.5 cu ft @ 32 Hz (with 9" x 1.5" port) and got just over 35 m/s for the air velocity!

You'll need more like 9" x 3" (or ~25+ sq in of port).

 

[Lurius 10+ year member]

How would I find the velocity of a 10.5"x1.5" port tuned to 35hz? WinISD is tellign me it would need to be 15.83 inches of port length.

 

[xluben 10+ year member]

If you have the correct version of winisd click on the tab that says "Transfer function magnitude" and go down to "Rear port - Air velocity" and it'll show you a graph of the port air velocity vs. frequency.

oh, btw, i think you have an old version of winisd in which the port length calculation is incorrect. mine says 24.75" long and the port air velocity is still 30 m/s //content.invisioncic.com/y282845/emoticons/frown.gif.a3531fa0534503350665a1e957861287.gif you need a bigger port (and thus a bigger box). also when looking at port velocity you need to make sure you plug in the power that you'll be giving the driver under the "Signal" tab.

 

[Lurius 10+ year member]

Alright, I took a look on WinISD on the rear port air velocity.. it peaks around 92ft/s after playign around with the port size, and the tuning. What would be considered an acceptable level in ft/s?

Thanks a lot, I really do appreciate the help!

-Lurius