How do I calculate PVC elbow into port length?

[Based]

I'm designing a box for a Boss P80DVC subwoofer. I want to tune it to 35hz. I figure one 3" aero port will be good. Well the calculator is telling me it needs to be 18.25" long. And I only have 12" of depth inside my box so I need to elbow it. How do I calculate the length of it into the total port length? And how do I calculate the flare into the port length? I'm actually going to flare the PVC this time.

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[Chris McNeeley]

Taking the time and money to build a box for a sub of that quality is pointless, not trying to knock you equiptment.

 

[Slo_Ride 5,000+ posts]

I'm designing a box for a Boss P80DVC subwoofer. I want to tune it to 35hz. I figure one 3" aero port will be good. Well the calculator is telling me it needs to be 18.25" long. And I only have 12" of depth inside my box so I need to elbow it. How do I calculate the length of it into the total port length? And how do I calculate the flare into the port length? I'm actually going to flare the PVC this time.

Yes. I always mock up the port then measure down the center from one and to the other including the elbow. An extra set of hands makes it easier.

 

[Slo_Ride 5,000+ posts]

I'm designing a box for a Boss P80DVC subwoofer. I want to tune it to 35hz. I figure one 3" aero port will be good. Well the calculator is telling me it needs to be 18.25" long. And I only have 12" of depth inside my box so I need to elbow it. How do I calculate the length of it into the total port length? And how do I calculate the flare into the port length? I'm actually going to flare the PVC this time.

Damn, the double post ninja for me.

 

[Based]

Taking the time and money to build a box for a sub of that quality is pointless, not trying to knock you equiptment.

I bought this sub just to be able to use it as a cheap sub that I can build a box for. Just to practice building boxes

 

[Based]

Yes. I always mock up the port then measure down the center from one and to the other including the elbow. An extra set of hands makes it easier.

Oh ok I understand what you're saying. So you don't measure the elbow by itself, you mock up the entire port and then measure it when it's done.

 

[Slo_Ride 5,000+ posts]

Correct. Because the two pieces of pipe will go inside the elbow an inch or so. Run a tape measure down the center bending it to keep it centered in the elbow.

 

[Based]

Correct. Because the two pieces of pipe will go inside the elbow an inch or so. Run a tape measure down the center bending it to keep it centered in the elbow.

How does the thickness of the wood effect the port length? Like if my wood is .75" do I add or subtract that to the length? Like say I have a 8" long PVC pipe and make it flared and it is mounted to the face of the wood. The PVC only sticks into the box 7.25" because of the .75" wood it has to go through. Does this mean that if the calculator says my port needs to be 8" long, do I need to have it sticking 8" into the box? Or does the thickness of the wood add on?

 

[Slo_Ride 5,000+ posts]

Just calculate the port length. The entire port can be outside of the box of you wanted.

 

[Slo_Ride 5,000+ posts]

This may help...

http://www.caraudio.com/forums/enclosure-design-construction-help/412621-guide-aero-ports.html

http://www.psp-inc.com/tools2.html

 

[NSTALN 10+ year member]

To find the length of a bend of pipe measure the inner bend and the outer bend and take the average. (both inside dimensions of course)

So if your PVC pipe inner bend is 2 inches and the outer bend is 6 inches, the actual length is 4 inches. Then just add that length to the length of the strait PVC pieces.

 

[Based]

Just calculate the port length. The entire port can be outside of the box of you wanted.

Oh ok so it doesn't matter

 

[BOOMINGRANDPA 5,000+ posts]

I'm designing a box for a Boss P80DVC subwoofer. I want to tune it to 35hz. I figure one 3" aero port will be good. Well the calculator is telling me it needs to be 18.25" long. And I only have 12" of depth inside my box so I need to elbow it. How do I calculate the length of it into the total port length? And how do I calculate the flare into the port length? I'm actually going to flare the PVC this time.

Yeah down the middle and some peeps run port 5 ft outside of box under and around inside car or whatever to tune lower port is port don't matter where it is.. be careful with that sub unless u wanta blow it or don't care I had friends boss in my box with my crappy amp had to turn everything down cause sub was about to come out of box (it's rated at like 1200rms or something stupid) can't handle more than 250

 

[BOOMINGRANDPA 5,000+ posts]

I'm designing a box for a Boss P80DVC subwoofer. I want to tune it to 35hz. I figure one 3" aero port will be good. Well the calculator is telling me it needs to be 18.25" long. And I only have 12" of depth inside my box so I need to elbow it. How do I calculate the length of it into the total port length? And how do I calculate the flare into the port length? I'm actually going to flare the PVC this time.

look at this pic http://img200.imageshack.us/img200/2034/p1070172d.jpg