Wow, I just wanna thank you for your help in my effort to build a good enclosure for my 12D4's. I've never been helped this much and I really appreciate it. You really know what your doing and I've learned a lot already. I think I'm gonna go with that last design you said with the slot port in the center. Since I need 1.75 Cubic Feet for each subs I guess I need 3.5 Cubic Feet for the total volume of the enclosure. If you have some knowledge of how that is wrong let me know but that's what the manual said to do. I also don't know how wide to make the port or how long. I guess I want it tuned 40Hz or less. Thanks again for all your help.