Found this on-line:

Subwoofer Size: 12”
RMS Power handling: 2500 Watts (undistorted power)
Peak Power handling: 5000 Watts
Recommended Box Volume: 1.2 cuft. (Sealed)
Weight: 16.6 lbs
Motor Type: Dual Gap / Internal NEO Magnet
Voice Coil Type: Ultra-High Temp Dual Coil (Made in the USA)
Voice Coil Diameter: 3”
Voice Coil Impedance: 1.5 ohm nominal per coil
Xmax (one-way linear excursion): 36 mm (3” peak-to-peak)
Maximum Excursion (one way): 46 mm (Almost 4” peak-to-peak)
Sensitivity: 96.7 db (2.83V / 1m) (coils in parallel)
Fs (Klipple-LSI): 31 Hz
Qts (Klipple-LSI): 0.81
Vas (Klipple-LSI): 47.7 Liters (1.68 cu ft)
Price: $2799.99

One thing that jumps out at me is that they give the sensitivity in units of (2.83V / 1m) rather than (1w / 1m).  Parts Express is doing this too.  The units are equal if you are talking about an 8 ohm speaker, but if the speaker is less than 8 ohms the (2.83V / 1m) units make the speaker look better than it really is.  This speaker, with two 1.5 ohm voice coils in parallel, has an impedance of 0.75 ohms.  This would mean that 2.83v across 0.75 ohms is equal to 10.67 watts.  The spec should read: Sensitivity: 96.7 db (10.67w / 1m) (coils in parallel),  which would translate into 86.4 db (1w / 1m), or 96.7 - 10log(10.67).

Compare with a 12" Dayton Series II that has proven itself to work well in a DB12:
RMS Power handling: 275 watts RMS
Voice coil diameter: 2-1/2"
Impedance: 8 ohms
SPL: 92 dB 1W/1m
Fs: 30 Hz
Qts: .35
Vas: 4.52 cu. ft
Price: $96.65

If I do the math for the max SPL I get 86.4 + 10log2500 = 120.4 db for the ul12 and 92 + 10log275 = 116.4 db for the SeriesII.  I'm no expert, and I have never even heard a sub similar to a ul12, but my guess is that you are paying dearly (in power) for the low Vas of 1.68 cubic feet and you really don't need that low a Vas for a DB12.  I might also guess that a 20% scaled up DB10 might work just as well and be half the size when you are done.  

BTW how much did you pay for the ul12? and what amp are you planning to drive it with?

DanK

Hey thanks guys, yea it's going into a hatch so savin space is good! I was fairly keen on building a 12" db because of spl, but if u think it will probably be less than a scaled up db10 or half wedge I will Check out those ideas. I was planning on running it with two response precision 1000w rms @ 1ohm monoblocks, one per coil. I will add a cap to it or maybe one cap per amp not sure yet. Let me know what ur ideas on the half wedge turn out like. And where can I find out info to scale the db10 up for the ul? David