There should be a location in the house where all the speaker wire ends are located so you can hook up some sort of speaker selector box. There might already be one built in with the audio system too. That would let you select which rooms or all of them to have audio in at once.
I've recently bought a house with bulit in speakers in everyroom. Each
room also has (what i can only assume) is a volumn control knob. All
the wiring for the whole house ends up in a central location.
The problem is the former owner didn't have a wiring diagram or any
specifications on the speakers. I'm no audio expert and am just
looking for a solution where i can pump audio throughout the whole
house from one source. I just have no idea where to start as far as
what equiptment I need to purchase to set this up.
Any feedback you may have to get me going in the right direction would