View Full Version : Extremely Confused.

07-27-2006, 05:16 PM
I have made many sealed boxes and (except for my first one) they have all turned out great. Sealed boxes won't win me any contests so i need to learn how to build ported boxes. I have made a few blueprints for 2 old systems of mine but they were to the exact specifications in the manuals for the subs. And this is where I become confused. Here are some questions that I have:

1. If the port length, width, height is stated in the manual do I have to use them in order to get the full potential out of the subs??
2. If not what are the things you have to look at when building a ported box.
3. How do you know what to tune your box to for a certain subwoofer???
2. What happens if I would make a box for two subs in the same air space? Would I have to double the height, width, legth of the port? Or triple them if I have 3 subs?? Or how on earth is that done???

Holy crap i am so lost that I don't even know what questions to ask. I have so many questions but I don't know how to ask them. If you guys have any suggestions to where I can learn a lot about this stuff please tell me. I would just ask for a design and then build it but that is kind of like cheating and I want to be able to say, "ya, it is all my handy work" when my friends asked who did it ;).

EDIT: and if you guys could recommend any good box frequency calculators I would appreciate it. Thanks

07-27-2006, 06:10 PM
I'm assuming you're numbering was meant to go into ascending order so I'll just go with my assumption:

1) Unless the sub is either very enclosure-sensitive, meaning the motor only works well in a certain box type/box volume, most manufacturers give you crappy parameters to work with so you'll have to do some searching to find out what port area and volume you will need to best suit your driver.

2) When building a ported box, you not only need to take the subwoofer into account but your goals/preferences as well. Some people prefer low-tuned, flat response bass while others prefer peaky, "I don't care how good it sounds, as long as it's loud" bass. Therefore as you might have guessed, low-tuning is needed for flat-response... NO, not always all woofers handle different tuning differently. What I have done in the past is I downloaded WinISD, put the Theile-Small parameters of the subwoofer I'm looking at into the database if not already there, and worked with the net volume and tuning to see what kind of transfer magnitude I want (guessing where cabin gain will affect the output).

3) Again, depends on your preference towards bass. The trend is that higher-tuned boxes are louder and more peaky at the tuning frequency and lower-tuned boxes are not quite as loud, but they have a flatter curve (oxymoron almost) which renders the sound output more accurate. What you can do is search and see which box setup will work best for your subwoofer(s). If you don't find what you're looking for then don't feel guilty for posting a new thread.

4) If you're building a box for two subs the easiest way to do it is to make a mock-plan for just one sub, then multiple one parameter (length, width, or height) by 2 or possibly multiplying two parameters by 1.413 (square root of 2) if you cannot double one parameter... then make some minor adjustments for board thickness and such.

What you want to do is first research what kind of box will work best for your sub(s). Once you have the box parameters figured out, such as Port Area (Av), Tuning Frequency (Fb), Net Volume (Vb) and Port Length (Lv), then start designing the box.

07-27-2006, 11:05 PM
Wow, lol, thanks man :D . That is very technical and exactly what I wanted to hear. That cleared up a lot of problems I had. Thanks.

07-28-2006, 12:03 AM
Pretty good calculator IMO ;)
Heard it takes driver and port displacement into account when figuring the volume.

07-28-2006, 12:19 AM
Port calculators, formulas, and other such widgets @ www.the12volt.com (http://www.the12volt.com).

*edit: there's that calculator! Been looking for that. The one @ DeCAF is nice.