Tuning round ports?

[AltarCrystal 10+ year member]

Alright, for my box, I"m gonna be running pvc pipe with flares (I'm making them out of adapters, cutting them off at the end of the expansion, and sanding them down) for my port for my sub.

Now, how would I go about tuning this? The calculator I found said a tube 3" wide and 7" long, is that 7" at the hole for the box? Or 7" total, some can be inside the box?

If I want to run two tubes, how would I go about figuring that?

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[Beginer 10+ year member]

Well 7" is port length. So pipe which you will use should be 7" length.

If you use two tubes so port area will be bigger and if you want to keep same tuning freq. you need use longer pipes.

For example if box is 2cu.ft. and port will be 3" width and 7" length, using one pipe, tuning freq is 32Hz. If you use two SAME SIZE pipes so tuning freq will be more than 40Hz... So if you want to keep same tuning freq (32Hz) with two pipes you need to use longer pipes.

 

[AltarCrystal 10+ year member]

Well 7" is port length. So pipe which you will use should be 7" length.
If you use two tubes so port area will be bigger and if you want to keep same tuning freq. you need use longer pipes.

For example if box is 2cu.ft. and port will be 3" width and 7" length, using one pipe, tuning freq is 32Hz. If you use two SAME SIZE pipes so tuning freq will be more than 40Hz... So if you want to keep same tuning freq (32Hz) with two pipes you need to use longer pipes.

Right, is there any calculators for tuning with dual ports? Would two round ports insted of one have any advantage/disadvantage?