How to protect the wood finish of speakers.

I think that I have heard of furniture treatments that contain sunscreen, anyone else know who makes it?

Only two viable options. Either cover them up as suggested, or invest in ultra-violet sunscreen film for your glass. I've got an 8' x 8' glass patio door by my system and installed sunscreen film. It cuts down on glare, enhances the energy efficiency of the door, and stops 99% of the uv light that damages fabric, wood, and art. Plus, it actually improves the view. It has an effect like wearing polarizing sunglasses, the sky looks much bluer.

2nd the Liquid Gold.This happened to my Virgos,when I lived in Wi.This restored the lustre.

Another wax product I use is Sunwax with UV protection...combines UV inhibitors with a unique blend of carnauba wax, beeswax and orange oil.

Bees wax is the best I have found. Liquid Gold can tend to dry out and require more applications. I have switched to a bees' wax product and buff it it lightly between applications. And as a accasional measure I use a citrus cleaner to remove any wax build up and re-apply the bee's wax. As a a final not I mean no offense to those who use Liquid Gold I used it for years and have just found something I like better.