Oh wow! Those are the old school Adire brand Maelstrom's. Boy....that takes me back.
They are pretty much an 18" version of the Tempest (which can be compared to the Dayton DVC15) and was a very nice sub driver but it just didn't sell well. Back then it was priced ~$300 and the Tempest was good for half that so you could see why it wasn't too popular at the time. About a year later Dan Wiggins released the XBL^2 system with the release of the Sadhara. I think that's what they called it (12" sub driver tuned to 20hz system in a tube) and then the much more popular and well know Tumult driver. The rest was history.
Lol...sorry, told ya it took me back.
I used to have the T/S on these but I think I lost them.
It did like a larger box than the Tempest and that I do remember. The Xmax was rated at 13mm and an RMS power rating ~1,000w.
EDIT: AHAH! Got the T/S specs for you.
Re 3.4 ohms
Le 3.5 mH
Mms 245 grams
Cms 0.24 mm/N
Rms 1.76 N*s/m
Fs 20 Hz
Sd 1180 cm^2
Vas 460 liters
Xmax 13.0 mm one way
SPL 92.9 dB @ 1W/1m
Pmax 550W per voice coil; 1000W total to the driver
Distortion <3%, 16 Hz - 200 Hz, @ 105 dB SPL
What kind of system did you want to build with these? Sealed? Vented? Passive Radiator? Horn?