When i hook up the radio just with side speakers it works good. When i add on the subwoofers it makes a humming noise. The side speakers keep on running fine. Ive checked the grounds to the radio and system. Cant seem to figure out what the problem is. It is a pioneer radio mp3. It work with old radio also a pioneer radio

 

Hard to say with out seeing it really, it sounds like a defective radio.
Does that radio have an auxillary input? Just wondering if you may have accidentally plugged into the wrong set of RCA jacks.

Can you post the model number of your radio? that may help bring some other suggestions.

 

Probably need more details.

For example... is it amped? (had to ask) And does the amp work?