what are the speaker sizes for an 87 conquest?

Starion Conquest Fanta Coke Killtodie ... just checking

I got a new head unit last weekend and i hooked it up and it all worked great up until the sound went out yesterday. I don't know a whole lot about stereos but i took the head unit back thinking that was the problem and swapped it for a brand new one and still no sound. i checked all the wire connections and there still good, they were soldered so they have good contact. And i checked the ground and that's still good. What could it be?!

At the end of the month it will be time for the National Cornbread Festival. Tons of stuff to do for the whole family, lots of food, vendors, street performers, street dance, music, cookoff's, carnival, and a classic car show. I will definitely be there although not in a quest. I'm going to try my darndest to have my 66 Rambler running, stopping, and bagged for this event. Proceeds from the car show usually go to some type of cancer research charity. It's not always on the website but Frida