Building a Dual 12 Ported Sub Woofer

djpartyboy, building a vented enclosure is an art and something I enjoy; I've built several for various sizes of drivers.  I'll list a few resources I use that will get you up and running on this project.  After learning all you can from these and downloading WinISD Pro or Unibox and getting familiar with how it works, you'll be at a point where you can try your hand at building your own custom ported box.  Besides this list, review threads on the subject from this forum by using the search function.  It will seem like an incredibly large amount of material to learn, but trust me it is an absolute necessity.  But, the simplest way to do it is to just follow the manufacturer's suggestions for the particular woofers you are using.  And blowntweeters is bang on target with the suggestion to get your feet wet first by starting with a sealed box.

• http://www.bcae1.com/spboxnew2.htm
• http://www.bcae1.com/carpetenclosure.htm
• http://www.bcae1.com/spboxad2.htm
• http://www.1728.com/pythgorn.htm
• http://www.diysubwoofers.org/faq.htm
• http://home20.inet.tele.dk/kou/ubmodel.html
• http://www.lalena.com/audio/basic/terms/
• http://www.hometheaterhifi.com/volume_5_2/cmilleressayporting.html
• http://www.carstereo.com/help2/Articles.cfm
• http://www.mhsoft.nl/spk_calc.asp#top  
• http://www.linearteam.dk/default.aspx?download=winisdpro
• http://www.pvconsultants.com/audio/frdgroup.htm

Some of these are valuable references that I refer to time and again.  Bookmark them, especially the calculators, for future needs.

Look at several manufacturer's websites like MTX for ideas on how you want your box to look.  If you want to use a slotted port instead of round, here is an explanation on how the conversion is done in a recent topic.  And while you're learning how to use WinISD, here is a thread on the subject that will help you "get it" easier.