wen i hooked up my speakers they sounded good but wen i crank up da car it...

[Thomas]

...like a whining sound. wat is it? wat could it be and y if possible

 

[odinsragess]

Ground loop. Make sure the grounds are perfect, to sanded bare metal, make sure you are using shielded/twisted pair RCA's. There are MANY reasons why this might be happening.

 

[eck210]

there are wires touching each other, that shouldn't be touching.
they are causing feedback. you may have to go back and see where there are other wires that touch the speaker's wires and try to keep them away, or separated.

 

[DaronT]

mine do that to when you accelerate do they do it even worse?

 

[~Superbad~]

it's either the ground wire or if your car has a stock amp, you have to try and bypass it because it causes that noise

 

[coleinalaska]

its alternator wine try a ground loop isolator or a better ground