What happens if you have too little or too much port area?

[Based]

I'm trying to come up with a box design for a CVR12. I want it to be 2.25 cubes net and I'm trying to use an aero port. The suggestion is 6" - 8" of port area per cubic foot so I need between 13.5 and 18 sq inches.

Since aero ports are fixed numbers, there's not a whole lot of flexibility to how much port area you can get out of them. If I use 2 4" ports, I would have 25". If I used one 4" id have 12.5". If I used one 6" I'd have 28". If I used 2 3" Id have 14". If I used 3 3" id have 21".

I can't find any 5" ports. And how do I get them to the length I need? What if I need to elbow them?

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[JonM]

I wondered the same thing. Does port placement matter?

 

[Hertz Mafia]

Areo ports u only need about 9" port per foot

 

[Based]

Is my math bad or do aero ports take up almost no volume in the box? I'm getting 0.1 cubes displacement for 2 3" aero ports each 12.6" long. A 20"x1.75"x28.46" slot port is 0.82.

 

[Hertz Mafia]

Is my math bad or do aero ports take up almost no volume in the box? I'm getting 0.1 cubes displacement for 2 3" aero ports each 12.6" long. A 20"x1.75"x28.46" slot port is 0.82.

Areo ports are space savers. I use the xplicit audio app.

 

[Based]

What if I need an aero port to be 19.5" long? The only ones I can find are 17" long

 

[ciaonzo 5,000+ posts]

A vent does not know or care what size enclosure it is in or what size subwoofer is driving it. The size of the vent has more to do with displacement, or volume swept, than it does anything else. If the driver is not a high power or high excursion driver, you do not need as much vent area. You will simply never reach the vent's maximum velocity capabilities. If the driver is a high excursion type, you will need lots of vent area. Too small a vent and you will most certainly experience chuffing or mach noises. Too big and the driver may unload above tuning with high power input, not to mention the pipe resonance effect.

This is why it is important to know T/S parameters and use design software. It will tell you these sorts of things. You can correlate Sd, Xmax, power input, and vent velocity all at once. You will know exactly what power input level, and at what frequency, you can expect to experience vent compression. This means you can design around it.

 

[Based]

A vent does not know or care what size enclosure it is in or what size subwoofer is driving it. The size of the vent has more to do with displacement, or volume swept, than it does anything else. If the driver is not a high power or high excursion driver, you do not need as much vent area. You will simply never reach the vent's maximum velocity capabilities. If the driver is a high excursion type, you will need lots of vent area. Too small a vent and you will most certainly experience chuffing or mach noises. Too big and the driver may unload above tuning with high power input, not to mention the pipe resonance effect.
This is why it is important to know T/S parameters and use design software. It will tell you these sorts of things. You can correlate Sd, Xmax, power input, and vent velocity all at once. You will know exactly what power input level, and at what frequency, you can expect to experience vent compression. This means you can design around it.

Oh ok thank you man.

I don't expect you to research this for me, but the sub this is for is a kicker 07cvr12. It's very old and very loose. It's xmax is supposed to be like 12.5mm but it looks like it moves way more than that. I'm just gonna try two 3" aero ports and see what happens.

This is what I have so far as my options :

-Cvr12 ported box

21.5x11.75x22 = 20x10.25x20.5 = 2.43 cubes

Port = 2 3" aero ports at 12.5" long 35hz 14.16 sq inch port area

Port displacement 0.1

Bracing displacement - 0.01

Sub displacement - 0.07

2.43 - 0.1 - 0.01 - 0.07 = 2.25

________

21.5x11.75x23 = 20x10.25x21.5 = 2.55 cubes

Port = 3 3" aero ports at 19.5" long 35hz 21 sq inch port area

Port displacement 0.239

Bracing displacement - 0.01

Sub displacement - 0.07

2.55 - 0.239 - 0.07 - 0.01 = 2.31