# Ported/Vented box equations?

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#### northumber82

Hi, I'm searching for ported box equations.

Knowing those parameters:
- All T & S of the speaker
- Box volume
- Port Number, diameter and length
- Mas, Cas, all Q (Ql, Qa, Qp), Ral, Rat

Need to calculate:
- Alpha
- H
- F3/FS
- Fb

In the book of V. Dickason there are tables based on alignments, how those values are calculated?

I can't understand well the Thiele and Small papers, can someone explain me the equations?

#### lousymusician

Hi, I'm searching for ported box equations.

Knowing those parameters:
- All T & S of the speaker
- Box volume
- Port Number, diameter and length
- Mas, Cas, all Q (Ql, Qa, Qp), Ral, Rat

Need to calculate:
- Alpha
- H
- F3/FS
- Fb

In the book of V. Dickason there are tables based on alignments, how those values are calculated?

I can't understand well the Thiele and Small papers, can someone explain me the equations?

I looked at the math once upon a time, probably in the 70's. I maybe calculated a sealed box for one wooofer, that was about it. These days it's easier for hacks like me to use one of the many box design programs like WinISD: WinISD to do the calculations. "Alignments" in the old-school sense are more regarded as special cases. With computer simulation all of the in-between cases can be modeled as well.

As I understand it, Hc/Hg and AlfaVC are physical parameters that can't be calculated from the rest. Hc/Hg are often specified by the manufacturer. Alfa depends on the material of the voice coil (Al vs. Cu).

I'm sure someone will step in to correct my errors.

#### Crashpc

Times changed. Nowadays raw F3 frequency doesn't mean much, and so on. Definitely start with simulations and check how each graph drawn is related to the other. Doing the math yourself is rather very unproductive, unless the simulation needed is not available for you.

#### Collo

I'm a fan of WinISD too. I've done an overview page if you're interested.

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This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.