I didn't get chance to take photos of the box for the 18", Ill get them tomorrow. It looks very similar to the 15" sub box though, with a little more bracing.
These are the prototype boxes that I got first. You'll notice that the baffle installation was different on the 10" and 12" and 15" box. I wanted to see which was the best way to go. I decided the larger box had the best method. I was worried that the inner baffle could cause an installation problem because it has to drop in on all 4 sides. If the box was glued up a little "off", it might not fall in really easy without a hammer. But I've put a few of these together and it doesn't seem to be a problem.
The shelf braces go all the way to the rear panel. But I designed them so you could cut a hole for a plate amp and still have plenty of clearance. I'll get some better photos with the top of the box removed. If you look close you can see how installing a plate amp would be very easy if you wanted to.
The one for the sealed 10" should be cheap and very easy to assemble. I had the company cut 2 different style braces, but the ones with heavy curves caused the 10" Titanic to rub on the magnet's rubber bushing. So they made the braces more squared off to increase the clearance. These will also hold a 12" driver. Again, the first baffle layer installs different on the finalized model, these were just prototype photos I took a little while ago. Bracing divides the panels at about 6".
This is about as simple as it gets: 1.25 cu ft
The box for the sealed 12" comes in around 2.25 cu ft if I recall. I forgot to grab my notes before I left work. These could probably be used for some ported 10's just by changing the baffle. The bracing clears most woofers with no problem. But I should ask them to make some with squared up braces to allow drivers with bigger magnets. Might do a 50/50 mix to be on the safe side. The inner baffle dropped in differently for this actual prototype. I didn't like this method as much because for some reason they didn't put rabbet joints on the top and bottom. The actual run does have them though, so it drops in place.
The box for the sealed 15" comes in around 3.5 cu ft, but I'll have to check my notes and post actual dimensions. It can also be used for some ported 12's. The box is 18" wide, 23" tall, and 20" deep. It can also be used for ported 12's. The photo of it by itself wasn't the best, so you can see these 3 side by side.
THIS is the way the other boxes now assemble. Notice that the first baffle will completely drop into the box so the outer baffle lays flush. Again, bracing is about every 6". This box can be dry fitted together with masking tape in less than 5 minutes!! Braces slide in pretty easy.