Converting 1 port into 2 ports

oldskoolmseriesfan · Post by **oldskoolmseriesfan** » Thu Oct 30, 2008 2:28 pm

Heres the sitch. With the size box I built (2.1 cubic ft internal) it calls for a 5in port 16.8 in long. Im using the box sealed right now but it sounds like garbage. This port will not fit in this box w/the drivers loaded. how do in convert this into 2 ports that give me the same as the single? im strapped for cash at the moment so im stuck with this box for now. ps had them in a previousely ported box they sounded awesome, no trunk space thogh. the port mentioned is tuned to 35hz. any help would be appreciated.

thedeal7235 · Post by **thedeal7235** » Thu Oct 30, 2008 5:37 pm

what about, 2 ports at 2.5 *8? sounds stupid, but worth a shot, can it sound any worse, if ur trying to save on space? what kind os fubs are these?

oldskoolmseriesfan · Post by **oldskoolmseriesfan** » Thu Oct 30, 2008 6:24 pm

thedeal7235 wrote:what about, 2 ports at 2.5 *8? sounds stupid, but worth a shot, can it sound any worse, if ur trying to save on space? what kind os fubs are these?

Ultimate T3 DVC'S. I was told these subs DONT like sealed enclosures, and that is definately the case. The optimum ported enclosure for these is 2.5 cubic feet with a 5inch port by 12.89 in. Same tuning frequency (35hz) but larger cabinet. I screwed up on my measurements and was left with the smaller box

just an off day Iguess. Is it that easy just divide it in half like that? It all equals out its worth a shot. Any Gurus want a shot at this? Thanks "thedeal7235" much appreciated. I'll try that 2moro if no one else has 2 cents to add. Ill make sure I relay back how it sounds

Post by **Jacampb2** » Thu Oct 30, 2008 7:21 pm

oldskoolmseriesfan wrote:
thedeal7235 wrote:what about, 2 ports at 2.5 *8? sounds stupid, but worth a shot, can it sound any worse, if ur trying to save on space? what kind os fubs are these?
Ultimate T3 DVC'S. I was told these subs DONT like sealed enclosures, and that is definately the case. The optimum ported enclosure for these is 2.5 cubic feet with a 5inch port by 12.89 in. Same tuning frequency (35hz) but larger cabinet. I screwed up on my measurements and was left with the smaller box just an off day Iguess. Is it that easy just divide it in half like that? It all equals out its worth a shot. Any Gurus want a shot at this? Thanks "thedeal7235" much appreciated. I'll try that 2moro if no one else has 2 cents to add. Ill make sure I relay back how it sounds

It doesn't work that way. It is about total cross sectional area of the ports, and the more port area that you have, the longer the ports have to be to maintain the same characteristics. If no one else chimes in, I will try to figure it out for you tomorrow.

thedeal7235 · Post by **thedeal7235** » Thu Oct 30, 2008 8:52 pm

yeah, i may not be right, but i have built 3 ported enclosures over the last year, and each one has sounded PHENOMINAL, but still, im no expert-1st one was a 3 hole 10" (diamond audio subs-ported d6s, then my old work truck, then i switched to the pg rsdc 10s(only 2 this time, in my personal vehicle-if noone else chimes in, see if jacamb2 will help you, he possess ALOT OF KNOWLEDGE!!! ( I began to take apart my old zx450(no output), and began to send him pics, even though I have never complted the repair, he is has always been very willing/knowlegable, ( its one thing for me to run wires, make boxes) , where he can give u specs on anything down to the last complete deceibel, u know what i mean, oh, and he also was able to give me the value for a bass cube remote part( he has built several by scratch for other phorum members-

KHPower · Post by **KHPower** » Thu Oct 30, 2008 11:46 pm

You could always try and build a slot port and then angle it inside the box to reach your tuned frequency. Sadly I am away from my good computer so I cant help you with BassBox pro

If no one else comes up with what you need Ill have numbers by morn

gkitching · Post by **gkitching** » Fri Oct 31, 2008 4:08 am

It has to do with the area of the opening. You can change the shape of a port. it's just a matter of keeping the same surface 'area'. Figuring the area of a circle is 'pi' multiplied by the radius squared. Or 3.142 x 2.5" x 2.5" = 19.365 square inches. So if you want a 2" wide slot port then divide 19.365 by 2". The height of the port should be 9.812". If you want a 3" wide port then divide 19.365 by 3" = 6.46". and so forth and so on. If you want 2 ports then divide the area you've figured by 2 and work that out.

I would use a slotted port because it is easier to 'fold' the port within the enclosure and keep it from limiting your mounting depth.

hehe .. Remember sitting in math class thinking 'when the hell am I ever gonna need to know this stuff"?

Post by **Jacampb2** » Fri Oct 31, 2008 8:35 am

I get two 3" ID ports at 12.611 inches long to maintain a tuning frequency of 35Hz.

Two 2.5" ID ports would come in at 8.4355 to maintain 35Hz, however, that is about half of the cross sectional area that you would have with 1 5" port, this will increase port noise, as the air velocity increases.

2 3" ID ports are about 2/3's the area, and will also increase port noise, but it is likely acceptable. The only way to get a shorter port with the same box volume, and the same tuning freqency is to decrease the cross sectional area.

If you want me to figure other diameters, just let me know and I will do it for ya.

Later,
Jason

oldskoolmseriesfan · Post by **oldskoolmseriesfan** » Fri Oct 31, 2008 9:35 am

Jacampb2 wrote:I get two 3" ID ports at 12.611 inches long to maintain a tuning frequency of 35Hz.

Two 2.5" ID ports would come in at 8.4355 to maintain 35Hz, however, that is about half of the cross sectional area that you would have with 1 5" port, this will increase port noise, as the air velocity increases.

2 3" ID ports are about 2/3's the area, and will also increase port noise, but it is likely acceptable. The only way to get a shorter port with the same box volume, and the same tuning freqency is to decrease the cross sectional area.

If you want me to figure other diameters, just let me know and I will do it for ya.

Later,
Jason

Jason, and everyone else you guys rock! Jason those other diameters would be great. My box is only 9in deep internally so thats what we got to work with. The box is in my trunk so I dont think the port noise would be a factor, the least amount of noise the better though. Thanks again, Dean.

Post by **stipud** » Fri Oct 31, 2008 9:36 am

You can use PVC elbows too dude

I would go with two 3" as well.

oldskoolmseriesfan · Post by **oldskoolmseriesfan** » Fri Oct 31, 2008 9:42 am

stipud wrote:You can use PVC elbows too dude

I would go with two 3" as well.

I could fire them one on each end aswell. Seen it on a straight from factory Kicker box with the one 5in. Both from same end would be better?

Post by **stipud** » Fri Oct 31, 2008 10:29 am

Yes, keeping your bass coming from the same plane minimizes cancellations. If you're totally desperate you can move the ports to a different face, but it's usually best to keep them on the same face as each other at the very least (same for the subs).

Post by **Jacampb2** » Fri Oct 31, 2008 10:54 am

I'm with stipud, the air doesn't care if it has to turn a corner or two (w/in reason). I would personally just build a rectangular port and put bend in it to turn toward the long end in the box. Also, if it helps at all, it doesn't matter one bit whether the port is fully inside the box or not aside from the fact that you gain box volume by placing the port partially outside the box.

Post by **bdubs767** » Fri Oct 31, 2008 11:00 am

you have to calculate for two ports though.....you can't combine the two to qoute on qoute work the same as one bigger port....

JL has a good write up on it
http://mobile.jlaudio.com/support_pages.php?page_id=165

oldskoolmseriesfan · Post by **oldskoolmseriesfan** » Fri Oct 31, 2008 11:56 am

Well thanks alot guys, I'm gonna go with the two 3in with elbows. That said I hope to have a report back 2 you guys this weekend. Ill try to get pics to but my camera only works when it wants to

oldskoolmseriesfan · Post by **oldskoolmseriesfan** » Sun Nov 09, 2008 5:09 pm

ok ive got the pvc elbows, do i measure the longest portion of the elbow to get its length? or is it a little more complex than that? any input would be great

Post by **stipud** » Mon Nov 10, 2008 7:24 am

Yeah, I usually measure the longest portion. I believe the corner slows down the air and drops your tuning frequency a bit more than normal, so the longest side is the most accurate. Either way it will fall well within the typical margin of error, and you shouldn't hear a difference.

KHPower · Post by **KHPower** » Mon Nov 10, 2008 7:50 am

I read a easy way of measuring the pvc port elbows or and kind of port elbows is to use a peice of kite string and then pull the string around the curve and use a marker on the screen then measure it on a ruler subtracting where the rest of the ports connect to it.

Post by **stipud** » Mon Nov 10, 2008 8:13 am

Hell, I just use the string to measure the total assembled port. That's about as accurate as you can hope to be. Any little tuning difference is not going to be audible.

KHPower · Post by **KHPower** » Mon Nov 10, 2008 8:57 am

stipud wrote:Hell, I just use the string to measure the total assembled port. That's about as accurate as you can hope to be. Any little tuning difference is not going to be audible.

True , I guess I didnt think of that. Now with using PVC pipe as your ports do you gentleman round of both ends to reduce the port noise and ubulance? I ask because although PVC is quite inecpensive , place's like Parts Express offer the aero port and many other ports which you can add the bends and curves and such

oldskoolmseriesfan · Post by **oldskoolmseriesfan** » Mon Nov 10, 2008 12:23 pm

Well, thanks again guys. Much appreciated.