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View Full Version : Round ports w/ port noise or slotted vent?



pacho
01-04-2005, 10:27 AM
I'm constructing a box for a Treo 18" SSX sub. The box is 5 cubic feet and being tuned to 35 Hz with 50 in^2 of port area. I was wondering if I use 10 round ports (3" Diameter by 5" length), will I have a lot of port noise and will the sub sound bad b/c i've never used round ports before. Or do you recommend I use a slotted port?? Thanks.

iceteebone
01-04-2005, 10:42 AM
well i'm not a box expert but i hear round ports have more of a tendency to create port noise and with a slot port box you would have more port area.

pacho
01-04-2005, 11:00 AM
Is there any way I could solve the port noise problem by using aeroports?? I could use 4 aeroports but then I have to have some more port area, maybe add one 2" Diameter X 4" Length round port w/ the aerports?

iceteebone
01-04-2005, 11:03 AM
i heard that the bigger the diameter the less chance of port noise. also i hear putting sound deadener on the port reduces port noise.

pacho
01-04-2005, 12:49 PM
I heard once that there's a way to round the edges of the port or something which will reduce port noise, is there any truth to this?

iceteebone
01-04-2005, 12:52 PM
I heard once that there's a way to round the edges of the port or something which will reduce port noise, is there any truth to this?


that's what i heard on slot ports when they make a bend inside the box.

hoss
01-04-2005, 12:59 PM
slot ports and round ports work exactly the same way. the only difference between the two is the shape. if you have the same port area figured, you have just as much likelyhood for port noise in each case. i myself would prefer the slot port just because of the fact that it is slightly easier to design and build. as for port noise though, that is totally dependent on the port area, and not the port type.

rounding the edges in the box will help a good deal. reduces air turbulance and makes a better path for the air to oscillate within. good for a tenth or two on the mic, and yes, it could help prevent port noise :)

pacho
01-04-2005, 02:32 PM
I'm probably going to go with the 10 round ports. If anyone can check my calculation-I would appreciate it. One round port is 3" Diameter X 5" length. Pie*r^2*h=inches^3. I want 50 inches ^2 of port area so I believe that would be 353 inches ^3. Pie*1.5^2*5=35.34 inches ^3 for one port. So that would mean I would have to use 10 round ports of 3" X 5" to equal 353 inches ^3 of port area?? Thanks.

pacho
01-04-2005, 11:02 PM
Can anyone check my calculations??

pacho
01-05-2005, 04:01 PM
Bump:

pacho
01-05-2005, 07:14 PM
I'm going to point the sub up in my car and I'll fold the seats down, but I'm deciding whether to face the port in the passenger area or towards the rear of the car. Anyone know anything about this?

Moe Lester
01-05-2005, 07:16 PM
IMO a slot port is a better idea than 10 round ports... and id give it more like 100 sq in of port

mobileaudio219
01-05-2005, 07:40 PM
If you fire the subs forward into the cabin then you can't put the ports firing back towards the trunk... Why not use a bigger diameter pipe (5.51") and use a just a couple of ports?

mrray13
01-05-2005, 11:53 PM
and u don't figure the length into the equation....a 3" round port has 7.06in^2 of port area..


so for 50in^2 of port, u will need (7) 3" round ports or one 2x25, 5x10, 3 3/38x15...yada yada yada ..slot port...


the length determines tuning...and multipling it in determines port volume, not area





wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee eee :peace:

pacho
01-06-2005, 01:13 PM
Alright, so instead if I wanted to use (4) 4" Diameter X 5" length round ports, would my box be tuned to 35 HZ or what equation can I use to calculate tuning freq? Mrray, wouldn't you have to put the length in the equation because to tell the difference between a 12" length aeroport and a 5" length that I'm using? And mobileaudio-I'm going to be pointing the sub up in my trunk and the ports firing into the passenger cabin with the seats down. Would this still sound as good as pointing the ports towards the rear of the car?

mrray13
01-06-2005, 05:38 PM
length determines tuning, not area. so in figuring the area of the port, length is not important UNTIL u determine what freq u want. then the area of the port can be manipulated to change the length to get the tuning.

and all this messes areound with box volume, which in turn changes tuning.




in this case, ur best bet is a slot port. u have a set size the box can be, ur ports are only so long...so ur gonna have to give up on something.



wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee :peace:

mobileaudio219
01-06-2005, 06:25 PM
Alright, so instead if I wanted to use (4) 4" Diameter X 5" length round ports, would my box be tuned to 35 HZ or what equation can I use to calculate tuning freq? Mrray, wouldn't you have to put the length in the equation because to tell the difference between a 12" length aeroport and a 5" length that I'm using? And mobileaudio-I'm going to be pointing the sub up in my trunk and the ports firing into the passenger cabin with the seats down. Would this still sound as good as pointing the ports towards the rear of the car?

http://www.bcae1.com/spboxnew2.htm

You can also download a free version of WinSID Pro Alpha... I dont have a link, but its easy to find with a google search...

As far as which way to point the ports, it varies depending on the car and set-up, but alot of people prefer to fire them towards the rear. I would take mrrays advice and go with a slot port...

pacho
01-06-2005, 08:37 PM
Alright, decided to use a slot port, 11" high, 5" wide, 18" long. 55 sq. in of port area. 35 Hz Tuning. Port area is .6 cubic feet if my calculations are right. Thanks for everyone's help.