Advice on replacing 12 in woofer in Martin Logan Monolith III's


I'm needing to replace the 12 inch woofers in my Martin Logan Monolith III's.  I am running a dBx 260 active crossover so I can control x-over points and output.   Any suggestions? 
stevepa
You would think this  measurement would be on the Internet. I've looked at MartinLogan site and around the net, but can't find it. 

No it's not, as I found. You'll just have to do it yourself as I did, wish I saved it all those years ago.

Cheers George
With a lot of advice and help from Tim (Timlub) I purchased a Dayton 12 inch driver. Since I'm running a dbx 260 active xover, I was able to to dial in the xover points and the slope,  it sounds amazing.  Also I added a SVS sub, which really brought out the lows.  Still have some room EQ I need to deal with, but overall it sounds awesome. Thanks Tim!