common ground

Is it possible to hook up a new head unit to a common ground system?  Can you hook up all the negative speaker outputs to ground and there rest of the wires as you would normally?  I don't think that you can make this work but I thought I would see if I can get any help.          What about using a psi2, has anybody used one for a common ground.

To put a new head unit into a vehicle with a common ground setup, you need to run new wires to all the speakers.

When I was installing professionally, a guy brought his boat to me, which had a common ground setup and he asked me about upgrading the speakers.  I told him I could do it, but he needed to upgrade the deck also.  He said he was trying to save money and only wanted to upgrade the speakers.  I told him it would play for a little while and quit.  He didn't care.  A couple weeks went by and he came back to upgrade his deck and speakers because it had quit like I told him it would.

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My ex once told me I have a perfect face for radio.