Sorry to hear about your speaker problem. You're correct, you shouldn't need to do anything special with your outdoor speakers over the winter, even if they get covered in snow. Our office is in one of the snowier places in the U.S., New Hampshire and we are used to snow here. The speakers should be able to handle it without a problem.
Our own Brad P, recently did a great video showing his Russound Rocks covered in snow in his backyard
Please call our Tech Support line toll-free at 1.866.888.7466. They'll be glad to help you out with getting these replaced for you.
