Box, port, big enough?

[sub-FATHER 10+ year member]

does the port allways have to have the 16 cubes per foot of air space of box?

will a 185 sqin port work for 12.3 cubic feet of box? this is without calculating the displacement of the sub

and with the total airspace of the box being 15 cubes with port deslacement, for 2 18s. what kinda problems could there be from the port being 11sqin to small.

Click to read more...

 

[7ender 10+ year member]

No it doesnt' always have to be 16.

12-16 is good for slots.

And if it's an aero, use ~half of what you would a slot port. 56% of a slot is what you can get away with with an aero.

 

[spltuscon 10+ year member]

12-16 is a good guideline, but SPL isn't an exact science so try to be close and you'll be fine.

The other thing to note is that, like mentioned above, it depends on the type of port. A basic slot port with minimal rounding will need to be a lot bigger than a high-flow version (whether aeroport or something else with good airflow). So if you have to compromise the sizing make it up with better flow.... bigger roundovers, smooth surface, no 90 degree angles, etc...

 

[SomeGuyDude 10+ year member]

Wouldn't that also mean that a thinner slot would be preferable since it could (theoretically) be done without a bend?

 

[sub-FATHER 10+ year member]

Its Actually A Slotted Port. I Have 2 Of These Boxes Stacked In A Wall In An Astro Van. All Four Subs Behind The Passenger Side And The Port Behind The Drivers Side. I Made It Out Of Two Boxes To Make The Port And Enclosure More Rigid With Less Flex Allowed. And Rounded All Sides On The Entrance And Exit Of The Port.

 

[spltuscon 10+ year member]

Wouldn't that also mean that a thinner slot would be preferable since it could (theoretically) be done without a bend?

Depends on the application...the general rule is to keep the ratio under 9:1, with the closer to square=the better. Most low tuned boxes (unless they're huge) have to round a corner and usually are thinner to make it practical. If that's the route you need to go, then you look at minimizing turbulence at the points of restriction; the inner mouth, any bends, and the outer mouth. 3/8" radius would be the absolute minimum you should ever use and of coarse more is usually better. If there needs to be a 90 degree angle in the port then you should add a 45 degree corner to the box side and roundover the port corner joint as much as you can. Think of it this way, a continous radius would be ideal since it wouldn't introduce velocity changes to the airflow in the port. I'll show you an example of something I've done to overcome this. Note that the end panel (which is the other port wall) isn't attached yet.

Finished pic

 

[SomeGuyDude 10+ year member]

Dayum dude. I'd be tempted to have ya build me one of those if you were in PA. //content.invisioncic.com/y282845/emoticons/laugh.gif.48439b2acf2cfca21620f01e7f77d1e4.gif

 

[sub-FATHER 10+ year member]

Depends on the application...the general rule is to keep the ratio under 9:1, with the closer to square=the better. Most low tuned boxes (unless they're huge) have to round a corner and usually are thinner to make it practical. If that's the route you need to go, then you look at minimizing turbulence at the points of restriction; the inner mouth, any bends, and the outer mouth. 3/8" radius would be the absolute minimum you should ever use and of coarse more is usually better. If there needs to be a 90 degree angle in the port then you should add a 45 degree corner to the box side and roundover the port corner joint as much as you can. Think of it this way, a continous radius would be ideal since it wouldn't introduce velocity changes to the airflow in the port. I'll show you an example of something I've done to overcome this. Note that the end panel (which is the other port wall) isn't attached yet.

Finished pic

thats a sweet *** box, how do you determine tuning?