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View Full Version : im stupid but I need clarification on this port please



twistedmind
07-30-2008, 09:58 PM
http://www.aww-kittah-aww.com/up/files/1089/portlength.JPG



is that measurment length per port, or is it over all length and I make each port to half that length?

SSS 18734
07-30-2008, 10:00 PM
That number would be the length of EACH port.

twistedmind
07-30-2008, 10:08 PM
seems awfully long considering its only a 2.3 cubic foot box, what m I doing wrong?

SSS 18734
07-30-2008, 10:14 PM
I doubt you're doing anything wrong unless you typed in the parameters incorrectly. That's actually a rather large pair of ports. What is it tuned to? Looks to be around 35hz according to your graph.

If you want to decrease port length, you can do several things.
1. Increase box volume
2. Use a single port
3. Use smaller ports
3. Tune higher

twistedmind
07-30-2008, 10:14 PM
okay so 2.314 cubic feet enclosure for one 12" fi Q

I need 36" of vent area per FI useing the 16" per cubic foot of volume ( they say I can use as low as 12 " per cube) , should use 12" to get a shorter port?

I just can't afford port noise as the ports will be less than 2 feet from my head.

and my box is only 21" deep, and im going to have to use square ports as its a glass box and I didn't figure for a slot port when I built it.

would a aero or multiple aero ports work better for me?

cycloneman
07-30-2008, 10:17 PM
What freq are you trying to tune to?

twistedmind
07-30-2008, 10:18 PM
I doubt you're doing anything wrong unless you typed in the parameters incorrectly. That's actually a rather large pair of ports. What is it tuned to? Looks to be around 35hz according to your graph.

If you want to decrease port length, you can do several things.
1. Increase box volume
2. Use a single port
3. Use smaller ports
3. Tune higher

I can not increase box volume as its fiberglass and done except for my square port inserts

Single port is a option don't know if I can get the necissary vent area that way though

Smaller ports are a option but I can't risk port noise

32Hertz is the manufacturers reccomended tuning for a daily musical street beater

twistedmind
07-30-2008, 10:20 PM
What freq are you trying to tune to?

32

IonSQL
07-30-2008, 10:25 PM
Are you trying to insert ports into a box that is already 2.3cf?

twistedmind
07-30-2008, 10:26 PM
i think im ****ed


if I make the port horizontal I have 28.5 total inches from wall to wall

if I go vertical I have 19.5 inches

the port can be no deeper than 3 " vetical mount

horizontal mount ive got some room to play with

twistedmind
07-30-2008, 10:26 PM
Are you trying to insert ports into a box that is already 2.3cf?

yes, I put off port calculations because I made the box from fiberglass and didn't know how big it would end up being

ill post a pic

twistedmind
07-30-2008, 10:28 PM
pic of box with measurments

http://www.aww-kittah-aww.com/up/files/1089/measurmeens.JPG

IonSQL
07-30-2008, 10:30 PM
Once you put the port in the box, it will no longer be 2.3cf.... it will be 2.3cf minus the space the port takes up :crap:

twistedmind
07-30-2008, 10:33 PM
Once you put the port in the box, it will no longer be 2.3cf.... it will be 2.3cf minus the space the port takes up :crap:



negative ghost rider, its sitting around 2.5 - 2.6 right now. I did my math a little small to account for port displacment.

SSS 18734
07-30-2008, 10:34 PM
I used a simple calculator to come up with a few figures.


You could use a 6" flared aeroport. That would give you about 29 sq.in. of port area and it would have to be about 29 inches long.

A 4x10 square port would give you a good amount of port area and would need to be about 40 inches long. If you tuned it a little higher to 35 hz, that number would drop to 32 inches.

Also, to reduce port noise without changing the box, direct the ports as far away from you as possible. Downfiring muffles port noise. Also keep in mind that you more than likely won't experience port noise during normal listening volume, even if the port is too small. It usually doesn't become apparent until it's getting pretty loud.

twistedmind
07-30-2008, 10:35 PM
i suppose I could side fire the port make it 2x16x24 "

but i really wanted he ports to fire towards the roof

actually I dont think that would fit, this blows monkey nuts

SSS 18734
07-30-2008, 10:40 PM
After looking at your picture, I think your best bet would be to use a 6" aeroport coming out of the lower left hand side and tuning a bit higher to 35hz or so. It would have to be around 23 inches long.

Remember that you can also use 90 degree elbows in order to make your aeroport longer. If you can get your hands on say, a 7" or 8" aeroport, you could use the elbow to extend its length inside the box. You could also do this with a square port.

twistedmind
07-30-2008, 10:53 PM
After looking at your picture, I think your best bet would be to use a 6" aeroport coming out of the lower left hand side and tuning a bit higher to 35hz or so. It would have to be around 23 inches long.

Remember that you can also use 90 degree elbows in order to make your aeroport longer. If you can get your hands on say, a 7" or 8" aeroport, you could use the elbow to extend its length inside the box. You could also do this with a square port.



what do you think about two 4" aero's at 25 inches long?

IonSQL
07-30-2008, 10:56 PM
if you put aeros in the side, won't the magnet hit the ports? Or are you going to mount inverted?

twistedmind
07-30-2008, 11:06 PM
if you put aeros in the side, won't the magnet hit the ports? Or are you going to mount inverted?

I honestly dont know, im going to have to buy a 4" piece of pipe and check it out. I suppose I could buy some elbows and snake the pipe throughout the enclosure.

im about to the point of scrapping this box kissing my 100 dollars worth of materials good bye and starting over

SSS 18734
07-30-2008, 11:13 PM
what do you think about two 4" aero's at 25 inches long?

That would work, but might not give you the port area you were hoping for at 25 sq.in.

Personally, I think it would be a better idea to use a single 6" port, and tune to approximately 34hz (You won't hear much of a difference).

Unfortunately, both of those ports will take up a decent amount of space. Both will take up about .4 cu.ft. of airspace. If your box is 2.5 cubic feet, you are left with 2.1 after port displacement. Lets say another .15 for driver displacement and you are now at 1.95 cu.ft. That will give you a final tuning of about 37hz. That is still a decent tuning, but will be noticeably more peaky than one at 32 like you were hoping for.

At this point, your options are to either:
1. Live with less port area in order to get it to your desired tuning, and try to minimize port noise by keeping the port as far away as possible.
2. Replace your 12" Q with a 10" driver so that you can better use the airspace you have.
3. Use a different subwoofer.



If you want to keep the 12" Q, the box that you have, AND maintain a 32hz tuning, your only choice would be to use less port area. Probably about 20-25 sq.in. total. Although I haven't used a Fi Q before, I think your subwoofer will still be plenty listenable with that port area. See if you can find some users with a box similar to yours, and see what they have to say about port noise.

twistedmind
07-30-2008, 11:50 PM
That would work, but might not give you the port area you were hoping for at 25 sq.in.

Personally, I think it would be a better idea to use a single 6" port, and tune to approximately 34hz (You won't hear much of a difference).

Unfortunately, both of those ports will take up a decent amount of space. Both will take up about .4 cu.ft. of airspace. If your box is 2.5 cubic feet, you are left with 2.1 after port displacement. Lets say another .15 for driver displacement and you are now at 1.95 cu.ft. That will give you a final tuning of about 37hz. That is still a decent tuning, but will be noticeably more peaky than one at 32 like you were hoping for.

At this point, your options are to either:
1. Live with less port area in order to get it to your desired tuning, and try to minimize port noise by keeping the port as far away as possible.
2. Replace your 12" Q with a 10" driver so that you can better use the airspace you have.
3. Use a different subwoofer.



If you want to keep the 12" Q, the box that you have, AND maintain a 32hz tuning, your only choice would be to use less port area. Probably about 20-25 sq.in. total. Although I haven't used a Fi Q before, I think your subwoofer will still be plenty listenable with that port area. See if you can find some users with a box similar to yours, and see what they have to say about port noise.




appreciate the help but it looks like im not going to be able to port this box at all, the way I want to.


my best option is 2.5 x 8.5 x ?? LMAO, and doing so is going to require a ton of work.


how do exterenal ports work? I still need to build my amp rack so I could hide a external port.

twistedmind
07-30-2008, 11:56 PM
okay, this is what im going to do, 3x10x27 external square port

another 25 bucks for MDF is a hell of alot cheaper than building a totally new box and throwing this one away