if neither speaker is working then the amp is bad, or not hooked up correctly. Please recheck your amplifier hookup, making sure that if your amplifier has two power wires, that both power wires are hooked up, and that the light on the amplifeir turns on when the power it turned on to the amplifier. 

if just one speaker is not working, then you would need to swap the amplifier speakers outputs that go to the speakers.
Disconnect the non working speaker from the amplifier
take the working speaker output on the amplifier, and switch it to the non working speaker, if that speakers starts working, then it is a defective amplifier
If that speaker is still not working, then it is bad speaker. 

​a crackling sound in both speakers could be a blown speaker, but more common would be the result of a bad amplifier or defective audio input cable. 

if the problem says in the same speaker, then the problem is a bad speaker

 Replacement parts are available here https://www.motorcycletunes.com/products/Replacement-Parts

http://www.motorcycletunes.com/warranty.asp