Building the Impossible? Wall Help

[Kevin M]

Let me say right off the bat that I feel like I am over my head when it comes to walls. I also want to mention that this isn't another one of those hypothesis threads where I ask a bunch of questions and don't build anything. I can fabricate but this is a project that has me out of my element and I need some help. Right now I have 2 18" in an Infinite Baffle setup on 240 watts. It sounds awesome and has some great extension and low end but it is not enough. I have been throwing around the idea for a while and I just ran out of reasons not to build it. (Rear-view Camera FTW) In any case we have passed the "entertaining the thought phase" and moved into the "determined to get the damn thing built" phase. I know you guys are anti-sealed esp. when it comes to 18's but I am looking for more cone area. Sooo, I guess I am asking if it is possible to put 5 18" in a sealed box in the 22-25cu. foot range. My thinking was I could put three at the bottom and two at the top. I would do 6 if I could get away with it. I don't think I have the space though. lol

I am going to start building it this weekend. The baffle is more or less the last part that is assembled right? My plan is to flesh it out with mdf making the walls 2 1/4" thick and the baffle would be 3". I plan on glassing the inside of the box and adding metal bracing (steel tubing) as well. Does this sound adequate? I know I will lose a couple cu. feet with that.

I really want to make this happen so I would really appreciate any help you wall buildin' vets have, even if you tell me I have to take it down a notch, or sell me on the idea of a ported box. I hate to say musical because that feels like a contradiction, but that's what I am after. Accurate response from 20 to 80 hz. One trick pony designs need not apply.lol

The frontstage is being redone with higher sensitivity mids and highs as well. The car already has a big 3 upgrade. (Run of 0 gauge) Still ridin' on the stock alt as well. That can wait for the moment. I would like to build the wall, get the rest of the drivers and get an amp before I do that. I can run my new fronstage and the 10" midbass in my doors off the amp power I have now to hold me over. They will be using the same amp anyway.

Here is the subwoofer in question. I am using two of them now. Badgeless drivers FTW.

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=295-475

You can check my build log in my sig. Here is a video of the system (which I also posted in my build log) as it sits to give you guys a little proof I'm not all talk. The wiring is a mess due to the fact I have been deciding how to finish it. I have only drove the car 6 or 8 times this month anyway so it was never in danger of a break in.

As you can see that's why I didn't enter in SOTM this time. Amprack and the baffle wasn't finished. I would have as I am only running 600 watts right now. 240 of that going to the subs. lol oooh. aahhhh. hhahaha. Seriously though, I do need some help lol