The enclosure is built out of 18mm MDF, and measures as a 406mm cube. The back panel is inset some 90mm to allow for the amplifier to be mounted in the rear. There is a terminal block mounted on the back to connect the driver to the amplifier.
The terminal block and cabling to the amplifier
This leaves internal dimensions of 370x370x280mm which results in a volume of around 33 litres, once the volume the driver occupies has been accounted for. The driver is front mounted, and will eventually have a grill covering it to prevent my cats from attacking the DPL12. I have finished the enclosure in solid rimu around 9mm thick on the 2 sides, 12mm on the front, and 15mm on the top. The top and side edges are routed with a 9mm round over bit.
Front corner detail
Rear corner detail
There is no internal bracing whatsoever, as the largest panel is 370x370mm and is "braced" by the amplifier mounts. The hole for the driver was made after the cabinet was finished (Though only sanded to around 80grit as I knew the router base may cause scratches as it was passed around a dozen or so times) using a router with the circle jig that came with it. I practised on a piece of 16mm MDF first to get the diameter correct - this piece later became the grill. The hole measured 304mm in diameter, and was 8mm deep. I then routed an internal hole of around 270mm diameter right through the front panel. The driver is thus recessed in and appears flush with the front surface. I then finished the enclosure, sanding down progressively to around 240grit, and then applied 3 coats of "Woody's Secret", an oil,wax, and polyurethane mix finish, rubbing down with fine grade steel wool between coats. The Woody's was applied using a rag, and rubbed in with a soft cloth. The natural rimu gives a great looking finish when oiled, and the polyurethane in the mix creates a more durable finish.
I am planning on removing the cork ring that came with the driver (Used I assume when one mounts the driver internally), as I prefer the finished look without it. This also allows it to be flush mounted in the way I have. I stuffed the enclosure with around 500g of Polyfill stuffing (The type sold in craft shops to fill pillows, cushions and soft toys) in order to increase the apparent volume that the driver sees. This, coupled with the Linkwitz Transform, should allow the sub to extend lower with more ease. The driver is mounted using 8 10g woodscrews which are around 25mm long. I spray painted them with 3 coats of gloss black enamel (Same as used on the amplifier board at the back) so that you won't see the silver heads. This is better IMO than purchasing black-oxide based screws, as the oxide coating tends to corrode with time and turns a black-rusted colour.
The back of the subwoofer with amplifier installed
The fuses and IEC connector for power to the amp
I have installed a layer of rubber weather strip around the inside of the recess that the sub fits into, sealing the cabinet fully. There are no leaks whatsover - this is critical in a sub you wish to equalize with a Linkwitz Transform. The grill is yet to be finished, but will consist of a piece of 16mm MDF (around 370mm square) that will be rounded over on the edges, and with a hole cut out the size of the driver (also rounded over) and painted flat black. This will be covered with grill cloth, and secured to the cabinet via push in grill clips. I have attached 4 25mm brown rubber door stops to the bottom of the cabinet, one in each corner, to act as feet.
The runner door stops installed as feet
Needless to say, the sub performs superbly. I have yet to add the Linkwitz Transform, and already the extension is incredible. When I first tested it out, using the "Shortcut to Mushrooms" scene in Lord of the Rings: The Fellowship of the Ring, a mirror almost fell off the wall due to the vibrations produced. I was a little worried about the damage I might cause to the room. Note that the driver itself was quite comfortable, it's just everything else in the room wasn't!