how to fugure what size vents for a box?
 

I was wondering if there is a general answer (way to find out) to figure how big of vent hole to size of box and size of sub? If anyone has a website they use please send me a link. Like a calculation of some kind

Also is there a huge difference to a tube vent that stretches to the back and a rectangle one that stretches to the back for the box then raps around?

Also is this ture? bigger the box deeper tone?


Thanks J

Tuning is done with space, port area, and port length, it doesn't just equate to "the bigger the box the lower the tune".

Use 12-16" of port area (L*W of vent) per cubic foot for daily. For SPL, use however much to get the desired tune.

With the same space, if you lower the port area the tune is lowered.

The longer the port length the lower the tune.

Most people either use approx. 16 square inches of port area per cube and a long port (wraps around) or use less port area and a shorter port. Some boxes are so big that you don't need port length and the 1-2" MDF width gives a 30-40hz tune (hole in a box using the same port area).

More port area = better air movement, so try to get it up to 16 (1:3 ratio max.) and change the length accordingly.

Google:
"port length calculator" - round & square
"RE box calculator" - shifty if using the second port length
"sealed box calculator"
"ported box calculator"
etc

Round vents don't need as much port area (10-14ish per cube).

It's easier to calculate boxes the "hard" way.

dumb

[QUOTEUse 12-16" of port area (L*W of vent) per cubic foot for daily][/QUOTE]

dumber


rbgnwa45 - don't take that personally, I know you did not make up either of those rules of thumb, but they are wrong regardless.

Personally, I like a nice speaker modelling program that gives me a graph of the vent speed vs. input power. Then i can determine what works best for my design. Winisd is free and has worked very well for me over the years. I hate rules of thumb!!!

WinISD is a decent box design tool but at the same time can overwhelm a lot of people.

For some guidance on vent design, check this link: PORT Size Calculations and Formulas for WOOFER and Subwoofer BOXES

Read it all here. Is it all about port velocity? Are you saying the best amount of port area can be drastically off from 12-16?

He's saying its not all about the box, more so about the sub(s) and how much air they are trying to move, at what tuning frequency. A 14mm xmax sub won't need as much port as a 32mm Xmax sub if they are the same size sub and enclosure. Yes, its about velocity, but the 12-16" rule sucks...

Does winisd calculate port velocity?

Deadlysones knows how it works.

Even better - a 6", 8", 10", and 12" woofer can potentially all use the same volume enclosure. Even without considering Xmax for any of those drivers, how can one begin to expect the enclosure would use the same size vent???

WinISD includes port velocity.