My guess that's not the case unless the speakers have been replaced and nigger rigged

Its possible that its just come loose or even rusted from the window being down during rain.

Lol anything is possible but it's unlikely. Like I said unless it was a shit install on new speakers.
It could also be a bad connection running through the door boot.

You're saying its unlikely that the connection on the speaker is loose but think its something in the door boot...?

is this happening in a honda civic? (srs)
i think i had the same problem as you

Did you ever fix it??

And more info, yes i changed it with a brand new radio.
And I don't know if it could be a lose wire, because it doesn't go off at all when it is below 50. But when it goes above 50, the sound shifts off and on.

What kind of car is it?
Have u ever replaced the speakers?

the smacking fixing it sounds like the connection is about to fall of or something. redo the connections and then try it.

1993 Ford Thunderbird. The audio is all stock. Never replaced the speakers.

Sounds as if its just a loose wire.