One speaker crackles when turned up

Ok I have 2 kicker 6x9s in my dear deck, and the right one crackles and pops when the audio is around 50% on the HU. I have both of the deck speakers running off an old 5 channel amp. I checked connections at the speaker and the amp and they seem fine.. What should I look for? I really don't want to put new speakers in there because pulling the deck out is a pain in the ass.