Tuning a Kerfed PORT HELP

[jdubbau 10+ year member]

Alright I am having a little trouble figuring out how to measure my port length for a kerfed port I am doing. Can anyone help me out as I dont want to go any farther on my box build until I can tune it correctly.

Here is a pick of close to what my box looks like except my port is all one piece that is also the front of the box as my port bends 90 degrees.

Click to read more...

 

[Vermithrax 10+ year member]

Unless I'm mistaken, you don't include any of the flare in the legnth measurement. The effective port would be the area where the width is equal. The flares would not be considered as part of the effective port.

 

[jdubbau 10+ year member]

Well that is pretty much what I have been doing but I have seen some people measure to the middle of the flair or a little ways into the curve?

This is why I wanted to make sure I did it right as it could add a few inches to my port if that is the case.

 

[jdubbau 10+ year member]

So I still dont know for sure and may have to add more to my port with another flair on the interior of the box to tune it a little lower so I will have to know how to measure it also.

 

[jdubbau 10+ year member]

Anyone KNOW for sure??

 

[jmanpc 5,000+ posts]

I always just measure from where the port reaches its final width.

 

[jdubbau 10+ year member]

OK I need a FOR SURE answer someone as I have all the answers covered below from three different responses and still dont know???

So far I have now been told

measure only the straight portion of port

measure some or half of flair with straight portion

measure ALL flair from start to finish

 

[ARSkemp 10+ year member]

i'm making a box right now and using half of flare, but i don't know if thats 100% correct, thats just what ive been told...

 

[springer 10+ year member]

only use the part of the port that is an equal distance apart. do not include the kerfed part. the kerf is not part of the port essentially, only there to increase the efficiency of the port. think of the port as a solid block of air and the front of it just like the surface area of the sub, it moves in and out of the port like the subs in the box. the wider part of the kerf will not move in and out like the equal width area. wait a minute..... i have no idea what i am talking about.... but it sounds good, right?

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[DBfan187 5,000+ posts]

Same way you tune a regular port, measure the length straight down the center.

 

[IDSkoT 5,000+ posts]

Same way you tune a regular port, measure the length straight down the center.

x2

It will change the tuning, but not enough for it to be audibly different. In order to find the absolute tuning, you'd have to do a bunch of trig work, and it's not really worth it. Just do regular length, and kerf the ends.