Hi,
The Peerless 830669 (Madisound) might be a candidate. Compared to the original specs you posted on another site, the sensitivity is close (89.8dB vs 89.3dB @ 2.83V) as are the Fs and Qts figures. I wasn't able to find anything on the 831812 at the Tympany site... even under archives. It's either real old or an OEM part number assigned to Gradient... or both. You may want to see what SB acoustics has to offer. I've been impressed with their woofer motors.