Thank you for your suggestion about the modem!
I think the problem may have been solved
The speakers, tv & modem were all on the same ungrounded plug.
I moved the modem to a different room where a grounded plug is available and hooked it up that way.
After doing that I no longer notice the crackling sound on my speakers. They seem to sound better in general as well. I'll keep testing it but as of right now it seems that the problem has stopped.
Thanks so much!