Mixing port sizes???

[jellyfish420 10+ year member]

i'll have some real world experiance in the next few days. i've got a box in my car w/ 1 18 ssd. i don't like the tuneing/port firing (up) so i'm blocking off the slot port. and putting in 5 pvc ports on the back. w/ 5 it'll be tuned @ 40, w/ 4 i'll be tuned @ 36, and w/ 3 it'll be @ 30. so we'll see what happens.......

 

[berserker 10+ year member]

Although, it isn’t standard practice, all you would have to do is add up your square inches, port area, and figure out tuning for said area and Vb. Then make sure all ports are of the same length in regarding mixing 6’s with 4’s.

 

[jellyfish420 10+ year member]

Although, it isn’t standard practice, all you would have to do is add up your square inches, port area, and figure out tuning for said area and Vb. Then make sure all ports are of the same length in regarding mixing 6’s with 4’s.

wrong

 

[oxsign 5,000+ posts]

wrong

+1, if you made them all the same size they would be tuned differently wright?//content.invisioncic.com/y282845/emoticons/wow.gif.23d729408e9177caa2a0ed6a2ba6588e.gif

 

[Flipx99 5,000+ posts]

I had the same question...

I *think* if the port length combined made sense.

Say you needed 98 sqin of port area.

Could you use 1 6" and 1 4" if the sum of the lengths was correct?

 

[jellyfish420 10+ year member]

I had the same question...
I *think* if the port length combined made sense.

Say you needed 98 sqin of port area.

Could you use 1 6" and 1 4" if the sum of the lengths was correct?

we just went through this in a diff thread...you don't combine port area w/ more than one port...say you have 2 ports you divide your net volume by 2 then figure each section, as having thier own port...

 

[oxsign 5,000+ posts]

we just went through this in a diff thread...you don't combine port area w/ more than one port...say you have 2 ports you divide your net volume by 2 then figure each section, as having thier own port...

I missed that thread. Do you happen to have a link to it to do some reading on what you guys figured out?

 

[Flipx99 5,000+ posts]

we just went through this in a diff thread...you don't combine port area w/ more than one port...say you have 2 ports you divide your net volume by 2 then figure each section, as having thier own port...

Makes sense.

I didn't see the other thread.

But it doesn't matter that the ports are different sizes...?

 

[berserker 10+ year member]

wrong

+1, if you made them all the same size they would be tuned differently wright?//content.invisioncic.com/y282845/emoticons/wow.gif.23d729408e9177caa2a0ed6a2ba6588e.gif

we just went through this in a diff thread...you don't combine port area w/ more than one port...say you have 2 ports you divide your net volume by 2 then figure each section, as having thier own port...

It would be just as if you used port area of an irregularly shaped port. Or even how you figure out tuning for other higher order enclosures, for example a ABC enclosure.

Also you can divide number of ports by Vb and go that route or you add up port area.

SquareRoot(A^2+B^2)= Total Port Area

 

[jellyfish420 10+ year member]

It would be just as if you used port area of an irregularly shaped port. Or even how you figure out tuning for other higher order enclosures, for example a ABC enclosure.
Also you can divide number of ports by Vb and go that route or you add up port area.

SquareRoot(A^2+B^2)= Total Port Area

if you just add the port areas it doen't come out right. doing it that way doesn't account for the fact that there are more ports...ie. more surface area(port walls) the vent air loses velocity along the walls. so if there is more walls, the air slows more changing tuning. do the math your self, you'll see it comes out diff. it's close and you'd probably never hear a diff by ear. but if its worth doing....its worth doing right:graduate:

anyway, the real reason i came back to this thread i was looking aroud the web at diff subs and ran across a sub that has a rec home ported enclosure using 2 diff size ports.....2 4" ports and 1 6" port.....hmmmmm

8.5 cubic feet tuned to 16 Hz, 2ea 4” flared vents 27.5” long, 1ea 6” vent 30” long, Line walls with stuffing

what do you know about that.....

 

[bigbang 10+ year member]

OK, two 4" ports, one 6" port.

2squared=4

2squared=4

3squared=9

Ratio of volume of box tuned to each port is 4:4:9

So just saying you had 1.7cubic feet of volume after displacement, each 4" port would be tuned to 0.40cubic feet, and the 6: port would be tuned to 0.90cubic feet. This is my theory of how you would go about tuning the different ports so that each one would be tuned by a certain volume proportional to it's own port area. And of course they are all tuned to the same frequency. Someone correct me if I am mistaken.

 

[spoonraker 10+ year member]

Makes sense to me