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netzero
08-31-2008, 05:19 PM
Hey all,

I've got a few quickies. I've seen people do boxes for two subs, one of each side of a common port. Where the port is T shaped, but no separator between the port that comes out of the box. How does this work and is it effective? Also, is it better when you have two subs to have a separator between the two and port them individually? Or have them in one big airspace with one larger port? THanks

hatemonger
08-31-2008, 05:25 PM
it depends on alot of things. most common, it comes down to space. the box will be larger with 2 ports and 2 chambers. some people like the looks of 2 ports. for a daily driver, it probably won't make much of a difference in sound.

GearGuy2001
08-31-2008, 06:32 PM
Like this
http://img.photobucket.com/albums/v157/GearGuy2001/caraudio/suboxalmostdone007.jpg
http://img.photobucket.com/albums/v157/GearGuy2001/caraudio/suboxalmostdone002.jpg

Yes it works :D

netzero
08-31-2008, 07:26 PM
Gearguy, yes just like that. Could you explain the tuning of that way? Like, with air moving together and out that port, does it change anything? And like, how is it treated, like two separate ports? I'm considering this setup to keep things looking smooth in my next box. Thanks

ps anyone with info on this type of box, that would be awesome!

tcguy85
08-31-2008, 07:29 PM
i would think that the back portion where it T's or splits off would be half the width of the longer part of the T.

hatemonger
08-31-2008, 07:31 PM
i would think that the back portion where it T's or splits off would be half the width of the longer part of the T.

the back part of the T is a seperate port for each. changing the width would change the tuning.

tcguy85
08-31-2008, 07:37 PM
the back part of the T is a seperate port for each. changing the width would change the tuning.

yea i know that. i'm not explaining what i am trying to say right i guess.

since the long part is being the port for both subs it needs to be wider than the other part i would imagine. the part where it splits off into two ports would be narrower than the other part.

hatemonger
08-31-2008, 07:39 PM
yea i know that. i'm not explaining what i am trying to say right i guess.

since the long part is being the port for both subs it needs to be wider than the other part i would imagine. the part where it splits off into two ports would be narrower than the other part.

you mean splitting the width of the front between the 2 in the rear?

tcguy85
08-31-2008, 07:42 PM
you mean splitting the width of the front between the 2 in the rear?

yes, the back part that runs parallel to the back wall would be half the width of the main section of port that runs the other way out the front of the box.

hatemonger
08-31-2008, 07:43 PM
it's the same concept as with aero's. i can't explain it in a technical sense, in a box tuned for 1 aero, you can't split the length and cut the aero in half and put in 2 ports. the length actually gets longer with 2 aero's instead of 1.

edit: after reading back on my own post, i think i may have succesfully confused myself.

tcguy85
08-31-2008, 07:52 PM
one part of the port is acting as a port for both subs, the other two parts are acting as a port for each sub. so the part thats acting as a port for both would be twice as wide as the parts that are acting like a port for each sub.

correct?

hatemonger
08-31-2008, 08:30 PM
one part of the port is acting as a port for both subs, the other two parts are acting as a port for each sub. so the part thats acting as a port for both would be twice as wide as the parts that are acting like a port for each sub.

correct?

no. in the end, there is just 1 port, but the box doesn't know that. you have to tune the box as if there is 2 slot ports, which, when you tune them with whatever port calculator you use, you would enter 2 ports, each of which is the same height and width. each port has to stay the same width all the way through the length of the port. you're seeing it as a bottleneck, but that's not the way the math works with tuning frequencies. i suppose this design could cause problems with air flow in a high power spl system.

GearGuy2001
08-31-2008, 09:32 PM
no. in the end, there is just 1 port, but the box doesn't know that. you have to tune the box as if there is 2 slot ports, which, when you tune them with whatever port calculator you use, you would enter 2 ports, each of which is the same height and width. each port has to stay the same width all the way through the length of the port. you're seeing it as a bottleneck, but that's not the way the math works with tuning frequencies. i suppose this design could cause problems with air flow in a high power spl system.

The Back "ports" are 1/2 of the width of the port you see on the front, also some people make a triangle piece to help divide the 2 ports and direct them out the middle port, I didnt and it works fine.

hatemonger
08-31-2008, 09:35 PM
The Back "ports" are 1/2 of the width of the port you see on the front, also some people make a triangle piece to help divide the 2 ports and direct them out the middle port, I didnt and it works fine.

so how do you tune a port that is 2 inches halfway and then jumps to 4 the rest of the way?

tcguy85
08-31-2008, 09:35 PM
The Back "ports" are 1/2 of the width of the port you see on the front, also some people make a triangle piece to help divide the 2 ports and direct them out the middle port, I didnt and it works fine.

thats what i thought.

hatemonger
08-31-2008, 10:47 PM
this is making no sense to me. 1/2 the port is 1 size and the other 1/2 is another size. the frequencies from the 2 subs won't magically stay on their 1/2 of the port. someone please explain why this works.

92c1v1c
08-31-2008, 11:37 PM
hey whats the spec of your box i want to make one like it...lol:)

netzero
08-31-2008, 11:49 PM
Thats what im saying, how does the middle port work? Would It just be easier to put a separator between the two and make two separate air spaces lol? I was just curious how it works and how to tune for it if it was effective.

GearGuy2001
08-31-2008, 11:53 PM
this is making no sense to me. 1/2 the port is 1 size and the other 1/2 is another size. the frequencies from the 2 subs won't magically stay on their 1/2 of the port. someone please explain why this works.

You find your Port Length for like a normal L Port box then extend it out so say your port length needs to be 15" to be X Hz

Now lets say your box is 12" Deep (Internally for ease of describing) and Your Main Port is 4"

So
http://img.photobucket.com/albums/v157/GearGuy2001/caraudio/demo.jpg

Between the Green Lines is 4", Between the Red Lines is 2", Between the Pink Lines is 10" (Total Depth of 12" minus 2" Red Lines Port=10) and the Distance between the Blue Lines is 5" since you need 15" of port length and you already have 10 (inbetween the pink lines)

netzero
09-01-2008, 01:33 AM
So, are you tuning each side to a 15" long by 2" wide port? And that will tune both sides to X Hz? I think i got it now, but doesnt that screw with the tuning, how the air shoots together before exiting?

hatemonger
09-01-2008, 10:42 AM
So, are you tuning each side to a 15" long by 2" wide port? And that will tune both sides to X Hz? I think i got it now, but doesnt that screw with the tuning, how the air shoots together before exiting?

the port is tuned to a frequency. which is what confuses me. you aren't tuning the air flow. i would think that each sub would see this as a single port, which would make it 2 inches wide on the back leg and 4 inches wide on the front leg of the port. i'm confused as to how you would tune a port like this. are you tuning a 2 inch port or a 4 inch port? this design makes sense to me if we were strictly just moving air. having the front port twice as wide as the 2 rear legs eliminates a bottleneck, which would help air flow, but i'm concerned about the ports frequency tuning, which has nothing to do with the air flow.

netzero
09-01-2008, 11:59 AM
Ahhh I see. The airflow has nothing to do with the tuning then, just turbulence is all i can see. But now I really wanna kno how to tune it with two different sizes too...

GearGuy2001
09-01-2008, 01:48 PM
the port is tuned to a frequency. which is what confuses me. you aren't tuning the air flow. i would think that each sub would see this as a single port, which would make it 2 inches wide on the back leg and 4 inches wide on the front leg of the port. i'm confused as to how you would tune a port like this. are you tuning a 2 inch port or a 4 inch port? this design makes sense to me if we were strictly just moving air. having the front port twice as wide as the 2 rear legs eliminates a bottleneck, which would help air flow, but i'm concerned about the ports frequency tuning, which has nothing to do with the air flow.

Look 2 Posts above this original Post I have a nice diagram that explains how to tune it

hatemonger
09-01-2008, 05:10 PM
Look 2 Posts above this original Post I have a nice diagram that explains how to tune it

i see that. it still doesn't make sense as to why. where do you find the math or the port calculator to tune it?