ok i have a small 200 watt amp hooked up to 2 pioneer 6x9 and after about 5-10 min theree is this really loud annoying whine thats comes in and the whine adjust freq. depending on how much throttle

whats is my prolem here ive been told i need a crossover but im not a audio person so im wanting a second opinion

 

Sounds like alternator since it changes with rpm. It gets higher pitched as the rpms go up correct?? Un hook the amp and see if it still does it to the non amped speakers. If it does it probably a ground problem with the radio. If its with the amp I would make sure the amp ground is a rust/paint free surface.