WILSON ORIGINAL SOPHIA'S

I've used Goo Gone and Denatured Alcohol (ethanol), with a plastic scraper (do not use metal). The process is very easy. To avoid getting any of the cleaning solvent on the driver(s), elevate one side with something like a towel, and only clean the glue off from the bottom half so the solvent cannot run into the driver (damaging the foam surround). Obviously, repeat the process working around each driver. On my first attempt, I taped around the drivers trying to protect them (and without elevating one side of the speaker), and it didn't really work that well. If you're careful, and you tilt the speaker (always working on the bottom side of the driver), you shouldn't have any issues. Make sure the speakers are absolutely clean before applying the pads (don't be in a rush).

@golfnutz is correct. Just have to take your time, use no metal tools. When you need a break, take a break. Its not a fast easy process. 

An easier way that completely avoids damage to the drivers is simply remove them. The only caveat there is if the leads are soldered. Not sure if they are or not on the Sofias. Doubt it. It will make the process much simpler and less likely for an expensive oops moment.