Crackling from Driver's door midrange speaker

[S4Mon]

Car is a 2012 with B&O system. The crazy thing is that it happens randomly! Some days it sounds perfect and other days it's so irritating that I "move" the sound to the passenger side. I think it is isolated to the driver's door midrange. Bass in music makes it very noticeable. I have all sound settings set to nominal.

Could it be a failing speaker or sound deadening material?

[Fresh.S4]

play a 100-200hz soundwave file from youtube.

[bandit]

replace the speaker. my friend at the dealer says its common for the speakers to take a dump