Use this Samsung members app and register your device. Then file a warranty claim. See if Samsung will help replace the device. Crackling speakers tend to be hardware related.
Have you visited the sound settings to see if any changes may be helpful? When is the crackling most obvious? For example, during speech, during calling, playing something treble or base. Connect a speaker by bluetooth to your phone. Is the music on the bluetooth speaker also crackling? How many apps are presently activated or running while the crackling occurs?