measuring port lenght...

[DBfan187 5,000+ posts]

dude i dont see why its so hard to tell me what 2 points on the box i measure for the port length... i havnt finished designin the box .....but if u arnt understanding what im sayin by measuring the port length i need a real boxer designer i guess

#1, don't be a dick. I'm trying to help you out, but all of your posts are half-assed, as in, you're only giving me a little info to go on.

If you would gimmie your dim's, I'd have something to go on. But you've neglected to tell 'us' your desired tuning, vB, ect.

What the hell do you expect?

 

[TrlcKed_OuT 10+ year member]

ok maybe this would be simpiler...if i was measuring a ported box to find its dimentions and tuning freg and port are ..i would measure the HxWxL of the box and the port...well if i measure the port width to be 15'' and the port height to be 5'' how would i measure the length of it??

 

[TrlcKed_OuT 10+ year member]

#1, don't be a dick. I'm trying to help you out, but all of your posts are half-assed, as in, you're only giving me a little info to go on.
If you would gimmie your dim's, I'd have something to go on. But you've neglected to tell 'us' your desired tuning, vB, ect.

What the hell do you expect?

well im not askin help on what length i need to have a certain freq.. if u werent tryin to figure something i already know and read my posts it would help.... i know that givin my box...which is 4.5cuft or whatever that with a port of 5''x15'' that to get a tuning of 35 i need a 25'' or so length those arent exact but i know how to get the tuing im just simplily asking givin a made box sittin in front of me how would i measure its port length.....what 2 points would i meaure from...refer to my drawing would i measure the red the blue or the green

 

[DBfan187 5,000+ posts]

ok maybe this would be simpiler...if i was measuring a ported box to find its dimentions and tuning freg and port are ..i would measure the HxWxL of the box and the port...well if i measure the port width to be 15'' and the port height to be 5'' how would i measure the length of it??

OK, now that's better. You said you want it 25" long or something...?
Take that 2.5", and measure it 25" down the middle, stay 2.5" away for all walls.

Help any? More?

If you would tell me your vB, and tuning your after, I could go into more depth.

 

[TrlcKed_OuT 10+ year member]

well i havnt planned it all out yet but i need to know that but its going to be like....57''xeither 15''or 20'' by 12'' it will have around 75-80 in2 of port with tuning around 35...but on the back side of the box its got a 7''x6''x57'' indent in it to fit into my truck.....but i wasnt sure how to make the port length when i actually build it...(first time builder here)

 

[TrlcKed_OuT 10+ year member]

is there a certain amount of room needed behind the end of the port wall and the end of the box.....say the port wall is 30 and the depth of the box is lik 40 and i need a 35'' long port length would 10'' be fine?? or did i lose u again lol

 

[DBfan187 5,000+ posts]

Add your port and sub displacement, to your NET volume.

Go here for your box dim's.

Like I said earlier, to measure the length, go straight down the center, ex. 4.5^3, 35Hz w/ 75"sq. of port, your length would be 27".

 

[DBfan187 5,000+ posts]

is there a certain amount of room needed behind the end of the port wall and the end of the box.....say the port wall is 30 and the depth of the box is lik 40 and i need a 35'' long port length would 10'' be fine?? or did i lose u again lol

port needs to be it's WIDTH away for the wall.
Say your port is 5" wide, make it 5"(2.5" will be the center point) away from the wall. Your 10" away, so you should be fine.

 

[TrlcKed_OuT 10+ year member]

ok thanks alot sorry bout all the troubles i didnt know how to explain it..one more question...does the port wall have to be equal to the port length or can it be less??

 

[DBfan187 5,000+ posts]

Port Displacement

if it uses of the sides of the box for one side of its port wall, then:

(port height) x (port length-wood thickness) x (port width + wood thickness) / 1728

if the ports in the middle of the box, and has its own walls, then:

(port height) x (port length - wood thickness) x [port width + 2(wood thickness)] / 1728

Port needs to be it's WIDTH from the walls, not length lol - WIDE *** PORT!