Originally posted by Deagle
I think what everyone is trying to say is that you won't notice the rears nearly as much as the fronts because you'll be sitting in the front and because of the acoustics of the car the rears tend to get drowned out. They do make some difference but don't make them your priority. What you should do however is stick to the same brand name of speaker because companies all have different approaches to sound.
I personally put the same speaker (coaxial though) in the rear just because I had the money and I tend to balance with a bit more rear coming through. I put Alpine Type-Rs in the front and rear. My alternative would have been to put Type-Ss in the back. They're one step down from the Type-Rs.
the reason i say no rear speakers at all are for a couple different reasons.
1- your car plays STEREO music. stereo is played in a two channel signal (right and left). so 4 speakers would be redundant right?
2- when you listen to a band for example, sounds come only in front of you. so why would you like to hear audio coming from behind you? this would ruin the potential good imaging you can have in a car.
3- along with the imaging. have the four speakers would be hard to time align them or make them plausible to your ears. sound travels at a certain speed (i forget how fast) but so with that idea, the rear speakers hit your ears after your fronts do. higher end head units try to combat this with time alignement.