-------------------- 2004 JEEP GRAND CHEROKEEC SPECIAL EDITION
STINGER 0 GAUGE INFINITY REF 6x9 IN FRONT INFINITY REF 6.5 IN REAR (3) INFINITY REF 10 SUBS STILL NOT SURE WHICH AMPS I'M GOING TO USE Posts: 89 | From: san diego | Registered: Sep 2002
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posted
with ports, all that matters, is the area and the depth. as long as you keep those two numbers the same, you can do whatever you want with the size/number of ports.
example:
if you take a 6cf box, and put a 12" deep slot port in it that's face measures 6"x16", you would get a 46hz tune. now, if we take that port and split it up into two 3"x16" ports that are 12" deep, you would still get a 46hz tune. the same would happen if you split it up into four 3"x8" ports, as long as they were still 12" deep.
in general, for spl... I think it is best to keep the ports as large as possible. less air velocity and less noise are a beneficial result also... for most people, they are best off using one large port. there are advantages to spliting up the port though.
example:
we take our box from above - 6cf with a 6"x16"x12" port. like I said, this would result in a 46hz tune. lets say that tuning on this box is a little high for ever day use, but it posts good numbers. well, an easy way to make it adjustable, would be to block off part of that port. less area = lower tune. there isn't a whole lot of nice ways to do this with one big port. you can use foam etc, but it's pretty hard to make it look nice. on the other hand, it is pretty easy to completely block off a port. lets say we split the port in half and see what that would do:
two ports 6"x8"x12" = the same area and depth from what we started. now, if we were to block off one of the ports we would end up with a box that is 6.4cf or so and it would then only have one port that is 6"x8"x12". with those numbers I get a note of 34hz, which will likely provide a much smoother response curve and a better sounding box. this can be quite handy if you plan on making a box that has a ton of port area for running it through the lanes, but can also be switched to a lower tune for every day driving... I have also noticed that ports larger than say 100cf start to push the boundry's as far as how musical they are. they tend to have a much steeper response curve, which isn't good for music. that's enough of a rant for now.
[ 02-20-2003, 12:38 PM: Message edited by: TGuY ]
-------------------- 2005 Black VW Golf TDI Alpine/DEI/Image Dynamics/CDT Posts: 736 | From: Albertville MN USA | Registered: Mar 2000
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posted
well i cant say for sure, but there is contradicting information regarding number of ports/tunning
taken from the jlaudio.com website, when you use multiple ports, you cannot simply pretend they all combined equal the same size as a single one. thier theory is that if you have two ports in a single box, in order to get the correct tunning, you have to divide that single box by the number of ports used, and pretend each port has its one box. for instance, a 6 cube box with a 25" sq in port and a second 25" sq is not the same as a 6 cube box with a 50" sq in port. you must divide the box by TWO in this case, so you actually have a 3 cube box with 25" sq in port and second 3 cube box with 25" port. tunning will be alot higher in this case if you use two ports. by thier theory.
i have never used two ports or compared them, so i cant say how it sounds....
www.jlaudio.com look under tutorials and then ports
Posts: 1854 | From: freezing in FAIRBANKS ALASKA | Registered: Aug 2000
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you get 25.818hz.. less than 1hz different... and this is going from one port to four...
if they think that there is any possibility of hearing a 1hz difference in tuning, then they are on crack. not to mention, the math given here is not not even close to accurate enough to make the comparison on paper worth while. real world, if you keep the area and the length the same, you will get very very close to the same tuning. it might make an audible difference though. that would likely only be the case if your talkin 100sqinchs+ down to like four 25inch ports or something more extreme than their example... in the end, like most things in this sport, it is trial and error. I would only recommend doing the split ports, if you're going to use it to make it easy to make a box tuned at multiple freqs. the most efficient design will likely be the most simple one and that is the one with a single big port.
[ 02-21-2003, 12:07 PM: Message edited by: TGuY ]
-------------------- 2005 Black VW Golf TDI Alpine/DEI/Image Dynamics/CDT Posts: 736 | From: Albertville MN USA | Registered: Mar 2000
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