aero port area compared to slot port area

[alaskanzx5]

Ok so iknow aero ports can useless port area with out getting port noise.

my question is how much less?

I've seen subs that where suggest by manufacturer 40-50" slot port but 20-30" aero port. That's roughly 30-50% less port area. To me that's a fairly big difference.

I think a 10-15% difference is more reasonable but that's why I'm asking.

[Krakin]

One thing to keep in mind is that formula definitely errors on the side of caution, you can probably get by with a little less than that. Things like flaring the ends of your port will help a lot. When I build I usually use a kerf bend at the port mouth to give a nice, large flare and I round over everything. If you can do that you can reduce your port area by about 30% and still avoid chuffing.

Earlier I mentioned there is a formula for calculating the effective area of a rectangular port compared to a round one, here it is:

D=(1.3*(X*Y)^0.625)/((X+Y)^0.25)

X and Y are the length and width of the port, doesn't matter which one is which.

D is the effective diameter of the port.

If you want to convert D back into area the formula is:

Area=(D/2)^2*3.14159

[alaskanzx5]

Ok, so if I'm doing it right according to that formula I would need a 10.65" port or equivalent. Roughly 10" less in port area.

roughly 33" more then suggested port area for round ports.

that's a big difference between manufacturer suggested and what that formula suggest.

with a proper flare and spacing is a lower port area then the formula suggests possible?

[Krakin]

Flaring a port allows a better transition of the air in the port to the air either inside or outside of the box.

The larger the flare the higher velocity the air can have without causing noise or other unfavorables. There is however a limit on how high a velocity that can be achieved for every size port.

Check out this site for a lot of info on port design.

http://www.subwoofer-builder.com/flares-25mm.htm

[kirill007]

Ok so iknow aero ports can useless port area with out getting port noise.

my question is how much less?

I've seen subs that where suggest by manufacturer 40-50" slot port but 20-30" aero port. That's roughly 30-50% less port area. To me that's a fairly big difference.

I think a 10-15% difference is more reasonable but that's why I'm asking.

Port noise isn't the biggest problem, screwing up frequency response and losing output is.

So don't try to use less port area, it will only bite you in the arse.

EDIT: The answer to your question is very dependent on a lot of variables.

So the difference could be 10-15% but it could also be 100%.

[Triticum Agricolam]

An important thing to remember is not all slot ports are going to work the same. A slot port 2" tall and 24" wide is going to be a lot less efficient than on 6" tall and 8" wide. The equation Krakin posted will show the difference. This could be why the manufacturers numbers were so different. I've seen design with some really high aspect ratio ports.

When it comes to port area you are much better off being on the high side of ideal than the low side.

[alaskanzx5]

Yeah I know, just trying to figure out what range of port area I need to stay in for round ports.

I know for square/slot ports I want to be around 90-120 and that I don't want it narrow because that can give an ill effect to the design. That being said I can go up to roughly 8x17.5.

I keep seeing people say that with an aero port you can use less port area because its easier to get an effective flare on them just unsure as to how much less is reasonableness.