32" of round port enough for 3.5 cf?

[I Like Waffle]

Looking at building an enclosure for a single cheap 15" and im figuring a good size would be 32" of port via 2 4" abs tubes 15" long. Box is around 3.5 net. Whats everyone think? Ive used round ports a couple times and they worked great, but im wondering if like 10" of port per cube will be fine for round ports?

Click to read more...

 

[d-REW 10+ year member]

32"? two 4" aeros comes to 25.12" id do three 4"= 37.68

 

[beany 10+ year member]

Curious, what equation does everyone seem to be using to find the volume of a circle port? Cause I seem to be doing it wrong.

 

[Bumpin' Goalie 10+ year member]

Edit: (Mental lapse)

R^2 x Pi = Area

 

[shizzzon 10+ year member]

lol, maybe for a 4" aero but that's the only size that would work for.

The proper formula for AREA, not Volume is Radius^2 x Pi(3.14)

Volume is- Radius^2 x Pi(3.14) x Length

 

[mazdakid 5,000+ posts]

4" would be 2x2x3.14=12.56

 

[Bumpin' Goalie 10+ year member]

lol, maybe for a 4" aero but that's the only size that would work for.
The proper formula for AREA, not Volume is Radius^2 x Pi(3.14)

Volume is- Radius^2 x Pi(3.14) x Length

Lulz good catch, lazy mental moment for me. Just did it in my head and had the 4" stuck where 2"x2" shoulda been. Gracias.

 

[beany 10+ year member]

Hmm, I've always been taught the volume of a cylinder is πr^2h, So in this case his 4" tube would be V=3.14(2^2)14=175.9?

Why is this so incorrect?

 

[Bumpin' Goalie 10+ year member]

When port area is discussed, the main factor is area of the opening. Too small=noise. Too big=a variety of issues.

When tuning is discussed, port length is then also included.

You need sufficient port AREA for a certain enclosure. Usually 12-16in per cube for slot port. Slightly less can be done for flared aeros.

Then once you have proper port area, you adjust the length to achieve the desired tuning.

 

[beany 10+ year member]

lol, maybe for a 4" aero but that's the only size that would work for.
The proper formula for AREA, not Volume is Radius^2 x Pi(3.14)

Volume is- Radius^2 x Pi(3.14) x Length

Okay so isn't the volume of a cylinder and area the same thing?

 

[Bumpin' Goalie 10+ year member]

Okay so isn't the volume of a cylinder and area the same thing?

Nope. Port Area is just the opening.

 

[mazdakid 5,000+ posts]

no volume is how much the whole port takes up

 

[beany 10+ year member]

Nope. Port Area is just the opening.

so when calculating the port area of circle ports is just that number before multiplying by the height to find volume, i.e. 6" circle = 9 x pi= aprox 28.26?

 

[I Like Waffle]

2x2x3.14 x 15" for the ports gives me pretty much 32" of port area, which is about 10 per cube. Ive heard of people using less, these arent flared though i assume that makes a diff?

If i do one 6" port i can get almost 36" of port area, think i should go with one 6" instead?