What does "are you using a slotted port" mean?

[cameron paterson]

What does "are you using a slotted port" mean on this website?

Port Length Calculator

Port length Calculator for sub woofer box design.

www.mobileinformationlabs.com

 

[ryanosaur]

Are you designing a port that is a slot port? Tubes with or without flared ends? Those are the two basic options.

If you are unfamiliar with slot ports:

That's a slot port.

 

[cameron paterson]

Why on this website when I plug in 7.5ft3 with a port of 3" x 16" tuned at 20hz does it say the length of the port is 37"?
https://www.the12volt.com/caraudio/boxcalcs.asp

And on this website when i plug in a square port at 7.5ft3 with a port of 3" x 16" tuned at 20hz it says 29" with a slotted port. And 37" without a slotted port?

Port Length Calculator

Port length Calculator for sub woofer box design.

www.mobileinformationlabs.com

 

[cameron paterson]

Which one do I use?

 

[ryanosaur]

I don’t trust online calculators.
Your numbers above don't make sense.
Is your cabinet volume supposed to be 7.5cu.ft?
Do you know the volume of the port you need to achieve the tuning you are after?
What are the actual box dimensions for your 7.5cu.ft internal volume?

 

[TLS Guy]

Which one do I use?

3" X 16" are the dimensions of the opening on the front of the sub below the driver. 37" is the length of the port. It is skating close to the wind to construct a port that long. A port that long, because the port resonance will be clearly audible and horrible if you excite it, as the port is an open organ pipe. The fundamental frequency of the port will be 177 Hz. If you cross at 80 Hz there still will be enough power to excite the resonance. If you cross at 60 Hz you will get away with it.

When you get ports that long, then you are getting to territory, where you need to tune with an ABR or two rather than a port. An ABR is an assistant bass radiator.

 

[cameron paterson]

Yes box needs to be 7.5ft3 after all displacements tuned at 20hz. Could I make the port smaller than 3" x 16"? I have an 18" in a 6.8ft3 box tuned at 20hz with a 3" x 16" and even at 20hz there is absolutely no chuffing. Could I do 3" x 13"? Don't the SVS PB16 only have 3, 3.5" ports? Thats less port area than 3" x 13".

 

[lovinthehd]

I'd use better modeling software than that site offers. Winisd or bass box pro etc.