I am trying to build the correct size retangular vent in my sub box. The specs per the sub manufactuer are listed below (in metric units)

Reflex Box
Vb= 28 Lit
Fb= 35 Hz

Reflex Tube
Ø= AR 65V
L= 155 mm
Does this mean the port needs to be 6 3/16" long with a 3" surface area (1.5" x 1.5")?

 

What sub is it?

 

Amp, sub, vehicle, music? What's that o with the slash stand for?

 

The sub is a Hertz ES250 single voice coil 10"

I have no idea what the 0 with the slash means I assumed it was diameter, but you know what the say about assuming

 

That is the symbol for diameter. I believe they are calling out a 65mm (2.5") diameter port.

 

Got my math wrong. That would mean an area of 4.9" so I could rebuild the vent to be 1.5" high by 3.333" long. Correct?

 

Somewhere around 29 cubic inches of port my friend

pi x radius squared x length

3.14 (1.25 x 1.25) x 6 (I changed your mm into inches btw)

 

Yes, you have the right idea.... you could make that port... or you could just get a 2.5" PCV and make a port with it. IMHO that is a pretty small port, even for a box that is barely 1cuft. What sub is it? I'd consider a 4" PCV tube, but you'll have to either keep port out of box, or add more internal space to the box to allow for the extra port displacement.

Not sure why you multiplied by 6.... the length has nothing to do with port face area.... only time you need that is to calculate how much space the port is taking up in the enclosure or tuning frequency.

 

[QUOTE=DeadlySones;635496] IMHO that is a pretty small port, even for a box that is barely 1cuft.

This was the reason for my OP. It seems like a very small port, but the info in the OP is copied directly from the box specification from Hertz.

 

Should be easy enough to find a 2.5" PVC tube. round it or flare as good as possible and there you go...