before you start cranking your system let everything warm up first. at least a good 15 minutes. i live in michigan so i never play my system in the winter unless its warm.
but a good trick to make the subs warm is to take a hair dryer to it. just get a pos 20$ hair dryer and heat up the sub with it and stick it in the port (if you have room to) and just leave it in there for about 2 minutes. it works for me.