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View Full Version : does WinISD calculate end correction into into port length?

IgnoreMe
10-04-2007, 04:56 PM
Originally Posted by winISD help manual
WinISD calculates port length assuming that there are one flanged and one free end, i.e. port is mounted to the wall of the box, and another end is freely inside the box. So end correction factor is 0.732 by default. Port length in box wall is counted to port length. If you want do convert the result to different end correction, then add 0.732 times diameter of the port to calculated port length. This gives you needed acoustical length of port. Then add end correction as you like

End correction
End correction factor is analytically or empirically determined factor, how much port extends beyond its physical ends. For free end, end correction is 0.30665 times port effective diameter. For flanged end, more analytical expression is available, 4/(3&#183;pi) ~= 0.42441 times port effective diameter. Flanged end is calculated assuming that tube terminates to infinite baffle. Which is not exactly true, but.. Following table summarizes various port configuration types and their total end correction factors (refer to above picture to various end types):

Summary of end correction values Port configuration end correction 1 end correction 2 Total end correction
Two free ends 0.30665 0.30665 0.6133
One flanged and one free end 0.42441 0.30665 0.7311
Two flanged ends 0.42441 0.42441 0.8488

Physical port length is obtained by subtracting port effective diameter multiplied by suitable end correction value from port's acoustical length.

**** is like for rocket scientists. all i want to know is:

1) if WinISD says my port length is 32" do i still have to add end correction to it, or is it already included in calculated port length?

2) what the **** is a flanged end? im assuming (from what i can get from that quote, that its just where the mdf over laps one another)

3) what does it mean to have "two free ends"?

dleccord
10-04-2007, 11:40 PM
take half of the smallest side of your port and add that to the port length, dont bother with the port correction ****; shits confusing as hell.

Mr Cabinetry
10-05-2007, 12:22 AM
End correction factor is big fukin waste because if ya do use it does nothing more than change the port tuning frequency of the port from that what you wanted to tune the port to in the first place.

Think of like this, say you have a port thats 4" x 16" height x 35" long tuned at a specific frequency, now take half the width ( 2" ) add that to the length of the port which will now be 37" long.

OK, now you changed 2 things, the box volume drops and the port tuning drops from what you originally wanted for the enclosure.

Granted, the change isn't all the great, but it's a change none the less, but, for the **** retentive's out there think and believe they will hear/notice the difference, yeah right.

Now i can see where this would have an impact on a competition level, but for the everyday listener that justs wants to bump, it ain't worth the sweat of crunchin numbers.

IgnoreMe
10-05-2007, 12:40 AM
take half of the smallest side of your port and add that to the port length, dont bother with the port correction ****; shits confusing as hell.

i know how to do it, i was just wondering if WinISD did it for you because, its a lot faster than me having to go by hand and calculator through the equation many times, if for instance, im trying to find the maximum box volume i can get while still keeping a low tune, etc.

mr. cab: yea that does make sense. however, if WinISD calculates it with end correction already included, then your not changing any factors since the rest of your box design, comes from the port length. now if it doesnt include it in, then i see your point that its better to just leave it alone.

W8 a minute
10-05-2007, 12:44 AM
Granted, the change isn't all the great, but it's a change none the less, but, for the **** retentive's out there think and believe they will hear/notice the difference, yeah right.

Now i can see where this would have an impact on a competition level, but for the everyday listener that justs wants to bump, it ain't worth the sweat of crunchin numbers.

x50 if it's in a trunk vehicle

dleccord
10-05-2007, 12:48 AM
End correction factor is big fukin waste because if ya do use it does nothing more than change the port tuning frequency of the port from that what you wanted to tune the port to in the first place.

Think of like this, say you have a port thats 4" x 16" height x 35" long tuned at a specific frequency, now take half the width ( 2" ) add that to the length of the port which will now be 37" long.

OK, now you changed 2 things, the box volume drops and the port tuning drops from what you originally wanted for the enclosure.

Granted, the change isn't all the great, but it's a change none the less, but, for the **** retentive's out there think and believe they will hear/notice the difference, yeah right.

Now i can see where this would have an impact on a competition level, but for the everyday listener that justs wants to bump, it ain't worth the sweat of crunchin numbers.

big fukin wow... ive never saw it that way in terms of an everyday listerner.

PSturmer
10-05-2007, 08:13 AM
dont use winisd for port calculation. only use it to find out your peak freq. even this measurement can be very inaccurate. a box tuned to 36hz was .1 quieter than 44hz when i played a 50hz tone. winisd said it would be a 8db difference.

use this site for designing
http://www.carstereo.com/help/Articles.cfm?id=31

it does end correction for you

Immacomputer
10-05-2007, 10:15 AM
dont use winisd for port calculation. only use it to find out your peak freq.

Winisd is very accurate in calculating your tuning frequency. Using it to find peak frequencies in an enclosure is a waste of time because of your cars transfer function. The reason why you got the results you have is due to you not understanding your vehicles transfer function.

IgnoreMe
10-05-2007, 11:05 AM
Winisd is very accurate in calculating your tuning frequency. Using it to find peak frequencies in an enclosure is a waste of time because of your cars transfer function. The reason why you got the results you have is due to you not understanding your vehicles transfer function.

so does it include end correction? :)