What affect does port area have on Sub/Box tuning

[I Like Waffle]

So im just now getting into tuning ported boxes and such, and im trying to figure out all the parameters and how tuning works so i can learn more about them. Right now im working on my first aero port box which is 2.5 cubes after all displacements with 2 3" ports 7 1/2 inches long, tuned to 38-40 hz.

The subs im building it for reccomends 14sq in of port area for 1 driver in 1.5 cubes tuned to 50 hz, but i decided to tune them to 38 for a little better low end. (hopefully they work good tuned that low). But when building a ported box what affect does port area have on the subs response or box tuning? Ive got the cutouts for the box done so hopefully itll work good with only 2 ports //content.invisioncic.com/y282845/emoticons/crap.gif.7f4dd41e3e9b23fbd170a1ee6f65cecc.gif What i still dont understand and cant get an answer on is when the manufacturer reccomends say 2 3" ports for 1 sub in 1.5 cubes, does that mean 2 subs in 3 cubes need 4 ports?

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[dB-SPL 10+ year member]

So im just now getting into tuning ported boxes and such, and im trying to figure out all the parameters and how tuning works so i can learn more about them. Right now im working on my first aero port box which is 2.5 cubes after all displacements with 2 3" ports 7 1/2 inches long, tuned to 38-40 hz.
The subs im building it for reccomends 14sq in of port area for 1 driver in 1.5 cubes tuned to 50 hz, but i decided to tune them to 38 for a little better low end. (hopefully they work good tuned that low). But when building a ported box what affect does port area have on the subs response or box tuning? Ive got the cutouts for the box done so hopefully itll work good with only 2 ports //content.invisioncic.com/y282845/emoticons/crap.gif.7f4dd41e3e9b23fbd170a1ee6f65cecc.gif What i still dont understand and cant get an answer on is when the manufacturer reccomends say 2 3" ports for 1 sub in 1.5 cubes, does that mean 2 subs in 3 cubes need 4 ports?

Flared ports are great in the fact that they almost completely eliminate any port noise (caused by the friction of air traveling thru the port). But to gain any significant port area from these, they require multiple ports. And to quickly answer your question, Yes. If a driver requires "X" amount of area, adding another driver would double it just like you would box volume. (If you have the space, that is.) Most high SPL guys will go with a slot type port simply because it's easier to gain much more port area as well as the ability to keep it all in one single port. You can keep a slot- ports noise down by simply sanding/routing the insides of the port. Any 'sharp' edges can make one annoying noise. However, with enough math, space and aeroports, you can achieve the same results with either box.

Hope that helps a bit.

-Bill-

 

[I Like Waffle]

so basically i should add another port or 2? I can add another 3" one but thats gonna be a pain as ill have cut up the front baffle and remake it. What kind of loss should i expect from having only 2 ports? I thought the box tuning had nothing to do with the number of drivers but wasnt sure, im still learning //content.invisioncic.com/y282845/emoticons/crap.gif.7f4dd41e3e9b23fbd170a1ee6f65cecc.gif

Heres a pic of the front baffle, everything is already cut out

 

[AllDayMJ 10+ year member]

typically the general rule of thumb to follow is 12-16sq inches of port per net cubic foot in the box. using the low side 12sq.in./ft. usually yields a more responsive and punchy bass closer to that of a sealed box, 16sq.in. yields a more "boomy" loose bass line.

for you box example, if you are using 2.5cubes net. you have a total of 14sq. in of port total..you'll definitely need more port area. more in the range of 35 square inches..

 

[WOT]

He doesnt "need" more port area, that box will sound just fine with no audible noise, none at all.

Ive went as low as 10sq in of port /cube with a slot port and the results were just fine

Following the factory recomendations is obviously best, but not always necessary

Your 2 ports will work just fine

 

[I Like Waffle]

Ok. Most i can add though is another 3" port, and do 3 3" ports 12 inches long. Would that be enough area? I can do either that or do a 3.5" x 11" x 14.5" slot port. Slot port would def be easier, what do you guys think about that? With that slot port id have only 2 inches at the rear of the port though for air to flow through between the port and rear wall //content.invisioncic.com/y282845/emoticons/crap.gif.7f4dd41e3e9b23fbd170a1ee6f65cecc.gif.

 

[WOT]

That is one rule Ive learned. Stay a MINIMUM port width, away from the endwall

2 ports you would be fine though

 

[I Like Waffle]

so you think itll be fine with just the 2 ports then?