No worries... think about all the times you listened to your car stereo speakers first thing in the morning during the winter.
I have a degree in Mechanical Engineering and work as a Process engineer in the Plastics industry. The only thing that would have suffered from the cold would have been the elastic elongation of the foam/rubber surround and the glue that holds them. If the surround looks fine then there is no problem. The other thing that could happen in theory is the metal wiring in the cross over could have expanded at different rates and pulled apart from each other (more so with aluminum than copper). But if that were the case they would not work...
Enjoy the speakers, most speakers are very tough!