Elemental Designs subwoofer build

[sn_85]

I've purchased the Elemental Designs 13Ov.2 Dual2 VC 12" sub already and now im looking to build the optimal box for it. I'm most likely going for the PE 500W BASH amp and doing a resistor change. For the project I'd like to keep costs and size to a minimum. I'd like to be able to get down to 18hz or lower (if possible) just as long as the internal vol is not to big. This is going to be a single driver, down firing, rear ported design. If I could beat or match a SVS PB12-Plus for ~40% I would be pleased as punch. Realistic goal? My room is 15'x13' with vaulted ceilings. Will be 95% HT.

I've been messing around with WinISD and the best I could do given the T/S is 20hz at around 4.4 cF (int vol). The int. vol seems a little too big to me. Looking at the ED website their A5-300 uses the same driver with a 550W amp and is tuned to 18hz +/- 3dB in a 3 cF box(internal volume).
http://www.edesignaudio.com/edv2/pr...products_id=103

This shows some of their custom box specs:
http://www.edesignaudio.com/edv2/index.php?cPath=72
For the 13ov.2 they've got 2.5 cF box tuned to 20hz.

Here are the T/S Parameters
Qts: .28
Qes: .30
Qms: 3.3
Fs: 21 Hz
Re: 8.3
Vas: 176 L
Mms: 195 g
Bl: 21.7 T*m
SPL: 89.1 dB
Sd: 545 cm^2
Xmax: 18.3 mm
Voice Coil: 62.5 mm

If someone could help me with planning out the box and getting it down in size I would greatly appreciate it. Thanks in advance