Car Stereo

My stereo system contans one pioneer head unit concted to one pair of 7inc. speakers and a pair of 6 1/2 in componet sytem. those speakers are powerd by the pioneer head unit (they dont humm at all).then i have 2 pioneer 6*9 powerd by a 400 watt amp. the 6*9 are the ones that humm. then i have one alpine type r 12 powerd by a 2,000 watt amp. the 12 inc. sub dose not humm. every thing sounds great but my 6*9. this is my 1996 z28 camaro. i have a optimo red top battery. plz help stop the nasty humming! thank you for your time.

1) the gains may be too high.2) you may have a bad amp ground.3) you may have a bad rca cable.4) the amp may be bad.5) a speaker wire could be shorting out.