If you have a cd player turn the balance from the front to the back. About -2 to -4 in the front and all the way up in the back. You could probably get a amp to run through the back speakers if you have money and want it to have more bass and clearer sound. If you have the stock cd player and dont want to buy an amp i would buy a after market cd player, probably one with a 50X4 built in amp, it will help the performance or the front speakers and the rear too. thats what i would recomend, i have a 4600 pioneer 50x4 cd player and 100 watt 6 1/2" speakers for my rear. It should be good when i put it in. Try what i said and if you have and questions ask.
Ucp's #1 Toyota Supra fanatic......still.
2006 Scion tC..
Forced Induction - Props to Dezod Motorsports & PTuning