Check design

[Girard747 10+ year member]

I was outside making the cuts for my box, when I realized that I wasn't completely sure about the port length calculations. I'm not sure if I'm right about the effective port length on this design. After measuring and accounting for end correction, I think it's 29.25", but I'm not completely sure. Worst case scenario is that it gets tuned lower than I expected, but I'd rather have it tuned where I wanted it...heh.

If someone could verify the effective port length, after end correction, being 29.25", that'd be awesome. Thanks.

PS: My MS Paint skills are a little rusty, and MS Paint has never heard of something called "proportions", so it's a little sketchy... heh

Click to read more...

 

[Girard747 10+ year member]

I was talking about how the length of the wood is different from the length that a calculator comes out with when you're designing the port. You know, how you measure 1/2 the port width in bends and stuff, but uh... I'll just assume I'm right and build it this way.

...and I just realized that i meant "effective", not active.

 

[Girard747 10+ year member]

All I was asking was for you to tell me if the effective port length is 29.25 inches. Am I completely wrong, or not?

 

[Girard747 10+ year member]

Sure...but no.

I'm not exactly sure what you're trying to say here... not that I'm the best at describing what I'm trying to say, but I'll be straightforward and sa that I'm confused with what you just said.

 

[PV Audio 5,000+ posts]

Because I don't know what you're asking. The port isn't even close to 29 inches long. I don't know what the "effective" port is, so I can't help you as to whether or not you are correct or no.

 

[Girard747 10+ year member]

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

The physical length of the port is measured down the dead center of the port from end to end. In the picture above, this would correspond to L1 + L2, but the physical length of the port isn't really what is important, it's the effective length of the port (with end correction) that is important

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).

Calculating end factor may sound like it would be more trouble than it's worth, but it's actually quite simple. To calculate end correction factor, simply add one-half of h to the physical length you calculated above (L1 + L2).

And you design boxes?

 

[PV Audio 5,000+ posts]

If you had just said end correction in the first place, it wouldn't have been a problem //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

 

[Girard747 10+ year member]

If you had just said end correction in the first place, it wouldn't have been a problem //content.invisioncic.com/y282845/emoticons/wink.gif.608e3ea05f1a9f98611af0861652f8fb.gif

I wasn't talking merely about end correction, I was also talking about the correct way to measure effective port length throughout bends.