Shitty attempt at an EDU thread...

[kickerlivinloud 10+ year member]

nvm

Click to read more...

 

[JohnBlayz142 10+ year member]

Or you can refer to the sticky at the top of the page:

http://www.caraudio.com/forum/showthread.php?t=215849

 

[slikrider20 10+ year member]

Excel is such a nifty program. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[Immacomputer 10+ year member]

Using only port area and plugging it into that equation will not be as accurate as using winisd. That equation will only really be accurate for round ports.

Also, you're misusing end correction. You do not add end correction to your port length but shorten your port wall to give the effective length.

Look at this drawing I made:

Let's say you wanted a port length of 19" for your desired tuning. Some people would make the port wall 19" if they could fit it. If the port was 4" wide, this would actually give an effective port length of 21" and thus lower the tuning.

the second image shows how to correctly use end correction. The panel now needs to be 2" shorter to keep the desired tuning frequency and calculated port length of 19".

 

[kickerlivinloud 10+ year member]

I was told on CAJ that you needed to add to the port length. I understand what you are saying and to subtract half of the port width makes since. I'm just confused b/c what was said on caj was well received from everyone there. In other words no one disagreed with it.

I'm just trying to figure out what is right. Right now I agree with you, subtracting half of the port width not adding it...

but what do I know?

Jon

 

[Immacomputer 10+ year member]

I would like to know how they came to their conclusions. It's not logical at all. My way is much more logical and correct. I don't know what CAJ (car audio junkies??) is but the people over there are wrong. That's all there is to it. It won't change tuning much (maybe 1hz or so) unless the port is pretty wide. In some cases, you could be adding up to 3 or more inches to the port length which could possibly be a rather significant change in tuning.

Here is a little bit about end correction from JL:

"The effective length of the port is found by adding an end correction factor. An end correction factor is necesary because more often than not, one wall of the port is also one wall of the enclosure and this wall extends beyond the end of the port thus effectively adding length to the port (remember, the driver can't "see" the length of the port, it can only go by what it "feels" is going on)."

http://mobile.jlaudio.com/support_pages.php?page_id=165

 

[JohnBlayz142 10+ year member]

When I started making enclosures back in 2002 I learned that with end correction, you are able to take off half the width of the port from your total length. So that's what I go with to this day.

 

[kickerlivinloud 10+ year member]

CAJ is caraudiojunkyard. Most of the member there are all from here. However I did not recognize who told me to add the port length.

Jon

 

[j3bus2k3 5,000+ posts]

Using only port area and plugging it into that equation will not be as accurate as using winisd. That equation will only really be accurate for round ports.
Also, you're misusing end correction. You do not add end correction to your port length but shorten your port wall to give the effective length.

Look at this drawing I made:

Let's say you wanted a port length of 19" for your desired tuning. Some people would make the port wall 19" if they could fit it. If the port was 4" wide, this would actually give an effective port length of 21" and thus lower the tuning.

the second image shows how to correctly use end correction. The panel now needs to be 2" shorter to keep the desired tuning frequency and calculated port length of 19".

//content.invisioncic.com/y282845/emoticons/fyi.gif.9f1f679348da7204ce960cfc74bca8e0.gif port length is a fuction of port area, net tuning and desired frequency regardless of port shape. 12in^2 is 12in^2. Rushing air knows no better. The ONLY forumla more suited for a round port is:

Lv=([8466.4R^2]/[Vb*Vb^2])-1.463R

I would like to know how they came to their conclusions. It's not logical at all. My way is much more logical and correct. I don't know what CAJ (car audio junkies??) is but the people over there are wrong. That's all there is to it. It won't change tuning much (maybe 1hz or so) unless the port is pretty wide. In some cases, you could be adding up to 3 or more inches to the port length which could possibly be a rather significant change in tuning.
Here is a little bit about end correction from JL:

"The effective length of the port is found by adding an end correction factor. An end correction factor is necesary because more often than not, one wall of the port is also one wall of the enclosure and this wall extends beyond the end of the port thus effectively adding length to the port (remember, the driver can't "see" the length of the port, it can only go by what it "feels" is going on)."

http://mobile.jlaudio.com/support_pages.php?page_id=165

If that isn't the most self-righteous statement ever said on here than I don't know what is...

 

[photocrazy8 10+ year member]

I have always gone with subtracting the length of the MDF like Immacomputer said. I baised my designing and building off how Moleste figures in end correction. I get the length of the port and then subtrack half the port width from the length of the MDF...

 

[Immacomputer 10+ year member]

//content.invisioncic.com/y282845/emoticons/fyi.gif.9f1f679348da7204ce960cfc74bca8e0.gif port length is a fuction of port area, net tuning and desired frequency regardless of port shape. 12in^2 is 12in^2. Rushing air knows no better. The ONLY forumla more suited for a round port is:
Lv=([8466.4R^2]/[Vb*Vb^2])-1.463R

If that isn't the most self-righteous statement ever said on here than I don't know what is...

Rushing air experiences turbulence. More surface area along the port walls and the corners in a slot port cause turbulence. Turbulence changes tuning frequency. //content.invisioncic.com/y282845/emoticons/fyi.gif.9f1f679348da7204ce960cfc74bca8e0.gif

I'm sorry but self-righteous statements are not usually based on fact but rather opinions. In this case, it is not my opinion that they are wrong, it is pure fact. Is it self-righteous to say that 2+2=4 and anybody who states it equals 34 is wrong? No, it isn't.

Care to try to prove my stand on end correction wrong? I hope you're not one of those people from that other forum.