If the problem is that your cables are picking up radio frequencies, a shielded cable could help. It doesn't sound like that is the problem since you are getting a crackling noise. You might have blown a speaker or have a loose connection. For many speakers, you can check whether it is blown (do not do this with the tweeter) by gently pushing in the cone while your fingers are spread out. The system must be turned off while you do this. If you feel or hear a rubbing noise, the speaker might be blown.
If your speakers are not built in to the walls or ceiling, you could test whether the cable is the culprit by unhooking the existing cable, moving the speakers near the amp and hooking a short cable to them to see if the problem replicates.
If your speakers are not built in to the walls or ceiling, you could test whether the cable is the culprit by unhooking the existing cable, moving the speakers near the amp and hooking a short cable to them to see if the problem replicates.