Thinking of building my own powered sub

Ok I've been looking around and thinking of building my own powered sub for my home theater. I've got my sub kinda picked out, just having problems choosing between two.

Im looking at the TC sound 12'' Epic and the TC sound LMS-R 12''. Im probly going to go with the Epic due to the lower wattage, so i do have to buy huge amp. If I go with the Epic im going to buy a Bash 500 watt plate amp. But if i go with the LMS-R I was thinking of buy the dayton 1000 watt plate amp, just dont know to much about dayton to know if there a good amp.

The only thing im haven problem with is a box design. I know the speakers are good to as low as 15hz, I just need a good ported box design that is tuned to 15 to 20hz. If anyone has any info on a box design please let me know. Ive built many car audio boxs but this will be my first home audio project.

Ok what ported box design would you or anyone recommend going with. I'm looking for plans with dimensions port sizes and port lengths, Ive been racking my brain all night and looking all over the net but haven't found anything. When I was building boxes for car audio I did trial and error. It was a hit or miss deal and I really don't wanna do that on this project. Im looking for something that will do 20 to 150hz or lower.  

well I got to looking around at box designs and i came up with some ideas.

The first one is 19'' H x 17'' W x 20'' D and two 3'' ports in the rear

The second one is based off the svs pb13 it 22'' H x 20.5 W x 27'' D with 3 4'' ports in the front.

What i haven't figured out is the port lenghts and the braces in side the boxes.

I have been up almost all night thinking about this firing my brain so if anyone has any ideas for a good box or could point me in a direction as to where i can go to get a good design that would be great.

I got started on my box today got everything cut out, glue and screwed together but the top. I have to finish cutting out my baffle and install ports before I glue the top on. The box I when with is pretty much the design of the SVS PB13-UTRA the only thing that I think is going to give a some problems is getting the port lenght right. I guess I'm just going to have to play around with some lenghts that i have calculated. Some of the lenghts may require me to use bends or 90s in the ports.

Does anyone know the lenght of the ports in a svs pb13-utra and how they are layed out inside the box? I do know that they are highflow flared 3.5'' port and that's about it.

Ok i used that tool to get my port lenghts, I wanna make sure Im doing this right, i put in my box volume my desired tuning (20hz) the port size and the number of ports with is 3 it gave me 70'' so i take that by 3 or is that the lenght each port needs to be, if so thats nutts! lol

Ok also when calculateing port lenghts do i subtracted the speaker vas from the box volume or not? I know I ask alot of question but its better safe than sorry i guess.

 Thanks for all your info and help robert

my box so far, the top is now glued and screwed on just waiting for the sub (LMS-R 12") and still looking at plate amps just need one big enough.

I decided on my amp finally after looking around for ever and calling many many places i think im going to go with a behringer ep seires apm. Just thinking Im going to get the ep 4000 so i have more watts to upgrade to more subs if needed. After looking around at plate amps i just couldnt find one that had the power i really needed. SVS wanted 599 for there plate amp, dayton wants over 400 for there 1000watt plate amp witch doesnt have a very good subsonic filter and peaple had to mod them, plus ive been told they dont make the power there rated at, then the bash plate amps werent powerfull enough and also had to have the subsonic filter moded. The behringer ep-2500 is 1200 x 2 at 8 ohms and 2400watts bridged at 4 ohms, the ep-4000 is 1400 x 2 at 8 ohms and 4000watts bridged at 4 ohms witch would be the max power for my sub or would give me room to build one more if i wanted. I sure haven more power than needed is better than not enough. Plus there cheaper in price. Little over 300 new like Robert said, thanks Robert! 

With all that said, I cut the hole for the LMS-R sub and im going out to get poly fill for the box tonight. I also couldnt wait to hear what the box was going to sound like so I threw a 12'' sub out of one of my infinity powered subs and powered it with the infinity amp too. The box hit the lows a lot better and smoother than both my stock infinity powered subs and didnt do to bad on the highs just could tell it needed a higher end sub and more power, it kind fell off on the highs at higher volumes and clapped a bit on the real low end. I just think at do to the lower line single voice coil sub that infinity uses and the lack of power the infinity amp has, that when a get the lms-r sub and the behringer amp, this box will wake up and sound awesome! I know that the infinity sub, amp and box are built and tuned to work together perfect, but it was a good test to see how the box would sound and respond. I'm sure it's going to sound and respond awesome with twice the sub and 3 to 4 times the power. Plus I built it with the 3 3'' ports at 23'' long to be able to tune it how i want it. Just like the svs subs. Just going to have to go to radio shack to get an rs analog spl meter to really tune it in.

This has been a fun build, just didnt know how much math and calculations went into building something like this. LOL lets hope it all works out in the end or this will be a costly lesson learned. lol

so what do you think about the behringer DSP1124 feed back suppressor/paramertic eq with the behringer ep 2500?

Robert what are your thoughts on the Marathon dj series amps, do you think they produce the power they say they do? That and what are your thoughts about the marathon eq's?

Hey robert I have a question about the behring eq, how do you hook it up to you receiver and then to your power amp? The eq doesnt have RCA or LFE connections. My Onkyo receiver has LFE and RCA style Pre outs, how would I hook all this up?

ok I know I ask alot of question but is the benringer dsp1100p as good as the 1124p cause i found one pretty cheap. Is there many differences between the two?