After having built a number of subs, especially the two 12" ones I built last summer, I can tell you that you won't be happy with 100dB at 20Hz for movies. You have to remember that 100dB at 20Hz sounds/feels much more quiet than 100dB at say 1000Hz. Don't get me wrong, I love my subs, but they don't even come close to being enough for movies. I have two of them, by the way, in a room much smaller than yours. For movies, you want to be able to hit 115dB. This is the loudness that will rumble and make you feel the sound like at a movie theater.
However, if you're set on using that 12, then I suggest you find a horn loaded subwoofer design. They are the most efficient and will get you the most dB for power, which you are strapped for with that amp. Instead, I'd look to design your sub to play to about 25 or 30Hz. You'll get much better results since you don't have to compromise the box design by getting it to play low.
Now, with that out of the way, I suggest as the others have that you ditch those parts. Buy yourself a Dayton RSS390HF, cheaper than the TC sounds epic, and build a Tuba HT
. You won't be disappointed. These play very low and very loud. They are large, but such is a requirement for low and loud in a big room. I don't have one. Instead, I built a clone of the JBL 4645C cinema subwoofer. It is huge, sensitive, and plays super low. There's absolutely no comparison when I put my two 12's against it. I reckon you'll have similar results with the THT.
As for building subs, Bill Fitzmaurice gives very detailed instructions when you buy the THT plans. If you don't want to build a horn loaded sub and instead opt for a simple box, all I can say is brace the living crap out of it. If you don't have a table saw or a good circular saw and a straight edge, buy your wood and go to a local cabinet maker. One of my local guys in Kirkland, WA quoted me about $50 for all the cuts I needed for the 4 speakers I wanted to build this summer. Don't bother with any fancy joints. Simple butt joints with Titebond II will hold fine. I panicked and used a nail gun to put finishing brads in the joints every couple inches. You don't need to do this if you brace and glue correctly. Also, use 1" MDF if you're going bigger than 2ft^3. 3/4" MDF vibrates too much and 1" isn't that much more expensive. NOTE: Be prepared for dust. Always wear a mask or respirator when working with MDF and close all the doors and windows near where you're working. You may not see it, but the dust gets EVERYWHERE and is a bitch to clean up.
Port: Don't use PVC for the port tube. It is over priced and doesn't paint easily. Go to Home Depot or wherever and buy a concrete form tube. A 4' tube will run you about 5 bucks and they're quite easy to cut. JBL uses cardboard tubes in all their professional subs; there's no need to pay extra for some fancy port. The same goes for port flares and the like. You won't notice the difference so don't bother with them, especially if you don't have good box building skills.
Bracing: You can certainly make some fancy CNC designed gobbledygook, but 2x4's work great. Cut them about an eigth of an inch long to pre-load (push out ever so slightly) the walls. Use 2 2x4's in a cross configuration every 2 feet. Glue to the walls and then screw them into place from the outside. Either countersink or drill out your holes to make room for the screw head and then fill the hole with spackle, Bondo, or wood putty.
Finishing: Depends on what you want. At the very least, prime the MDF or seal it before putting a finish on. Nothing sticks well to MDF and the ends will soak up paint like no other. Sand the edges as fine as you can before putting primer or sealer over. Then, sand again until it's the same smoothness as the surfaces around it. A lot of people finish their speakers with Duratex, but that may not be the best for putting in a chic living room. You have to choose on that one. Veneer, paint, vinyl wrap, etc. are expensive and the cost adds up quick. Factor in between $100 and $200 to finish it.
Amp: I'm not sure if that amp will play a THT to its loudest, but that's a decent amount of power. You should be fine, but don't expect miracles. Tried and true sub amplifiers are the Behringer EP1500, 2000, 2500, and 4000. Tons of power, tons of reliability, and they actually put out pretty close to as much as they say. Don't forget that you want headroom in your amp for 3dB spikes. If your speaker is rated for 500W, get a 1000W amp. If you turn your sub up to watch Transformers or something of the like, you'll want that headroom in for all those Michael Bay explosions. If you don't have that headroom, your sub will clip and sound like junk.
EQ: Depending on how you design your box or if you go with the THT, you'll likely want some form of EQ to extend a bit lower. The Behringer DSP-1124P is the holy grail of sub EQ. It's mega cheap and works great, what more could you ask for? If you use the THT, give it a 6dB boost at 20Hz and you'll be good to go. You may see some over-excursion, but it won't kill the driver and you won't notice the distortion.
Lastly, get some good spikes or pads for the sub to get it off the floor. Anything from this page
will work great. Don't buy the ones from Parts Express; they're way overpriced. If you're on hard flooring, get some foam yoga/exercise mats - the thick kind - and stick them under it. You won't see them, the sub will look like it's floating, and it'll sound much better.
This is all I can think of off the top of my head. If you're really stuck to the TC driver, I'm sure you can make something great. But in the world of subs, displacement is everything and the smaller drivers simply can't produce as much as the big ones without a lot of excursion, which comes at a very high price. Do yourself a favor and ditch the TC sounds, grab the parts/plans for a Tuba HT and be on your way. Look around the web for a used Behringer EP amp. Ebay, Craigslist, and the classifieds here are a good start. Don't pay more than $250 for the EP2500,4000 and no more than $200 for the EP1500,2000.
Follow what I've advised and you'll have a bomb-diggity sub without breaking the bank. Expect to be out around $600 when it's all said and done.
Another idea, depending on where you're located, is to just buy a good sub. This
is the same sub I have. It's used in many movie theaters around the world and sounds, simply put, epic. It won't play below 20Hz, but the stuff you get 20Hz and above will the the best you've ever heard. New from JBL these are around $2000, so this one is a lucky find. I'd look into the cost of shipping, or see if he'll part out the driver to you. If you go this route, PM me and I'll give you all the information you need to clone it with that 2242H driver. It'll probably cost you about the same as if you went with a custom design, maybe a bit more, but not much. I got the 2242H driver for $300, and built the box for about $75. I'm using a Behringer EP2500 bridged mono which I got for $200. Turned up half way this thing is scary. Those prices add up to about what it'd cost you to use the TC sounds, the SPA500, and a custom box with finishing.Edited by Frosteh - 9/29/12 at 9:49pm