# winisd multiple ports

nodiggie
Copper - Posts: 69
Joined: August 19, 2009
Location: California, United States
Posted: October 28, 2009 at 11:37 AM / IP Logged
After reading the instructions thoroughly and searching all winisd topics, I was able to get the program working just fine. I was NOT able to find the answer to my question.
My question is: when calculating 2 rectangle ports the total length shown by winisd is nearly doubled. Is this the correct length for each port? or do you divide that figure in half for each port? Thank you for your help and knowledge.
Still learning
Kraco
whiterob
Copper - Posts: 351
Joined: July 22, 2007
Location: United States
Posted: October 28, 2009 at 2:30 PM / IP Logged
It is the length of each port.
nodiggie
Copper - Posts: 69
Joined: August 19, 2009
Location: California, United States
Posted: October 28, 2009 at 3:24 PM / IP Logged
Thanks for the reply. Since I was building a single driver enclosure, the dual ports calculation was confusing me. I think I should stick to single port. I'm not certain. This is a endless learning adventure.
Still learning
Kraco
stevdart
Platinum - Posts: 5,816
Joined: January 24, 2004
Location: Pennsylvania, United States
Posted: October 28, 2009 at 5:30 PM / IP Logged

Don't let it confuse you.  When you increase the number of ports you are also increasing the total port opening area (in square inches).  For the same tuning frequency figured for just one port, the length- now- of the two ports will necessarily be about twice as long as that single port would have been.  It's because of the increased port opening area.

Now, if you were to reduce the diameters of the ports you could reduce the overall port length.  Use the graphs in the WinISD program to monitor rear port air velocity (port noise) as you make your design compromises.

Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.
nodiggie
Copper - Posts: 69
Joined: August 19, 2009
Location: California, United States
Posted: October 28, 2009 at 9:32 PM / IP Logged
Thanks again very much. It is a blessing to have access to such knowledge. You guys ROCK !
Still learning
Kraco

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