Man this has been driving me nuts for months, often resulting in me just flat out not listening to any radio.
Basically, at intermitent times (seems to be worse/ more frequent in wet weather) my front RH speaker will make the most horrible crackling noise I've ever heard from a speaker, meaning I have to turn it off just to keep my sanity. At first I thought it was due to bad weather and water getting into it, but it also occasionally happens during the really hot days.
Then I thought maybe it's the speaker itself, being 30 years old I thought this must be it... So I changed them for brand new ones and it went away for a while. Then all of a sudden on a wet evening it happened again!
Here is a video of it happening: https://www.youtube.com/watch?v=3oY7ul6XmJc&feature=youtu.be
Any thoughts? It's driving me nuts!