I wanted to have three zones, one for the cabin, one for the cockpit and one for the stern (swim platform) speakers. The change was straightforward and luckily did not require pulling new wires. This change is such a quick and free improvement that i am even wondering if the installation was done incorrectly. To make the change all I had to do was to remove take four screws that hold the MS-AC700i, move the unit a bit, reconfigure three wires put the unit back in place.
In case you decide to make such a change, here are the details. The original speaker wiring configuration in my boat was as follows:
1) Cabin: speakers connected to Zone 1 internal MS-AC700i amplifier
2) Cockpit: speakers connected to FM-504, which was connected to Zone 2 low power output
3) Stern: speakers connected to Zone 2 internal MS-AC700i amplifier
All I did was to move the three RCA connectors, of Item 2 above, to the Zone 3 equivalent. After doing that I had to go to settings to enable Zone 3 and name it. I also made sure the zones are not linked, not linking the zones was important to me because I want independent volume control. If all you want is to have fixed but different sound volume in each zone you could keep them linked.
I am new to the forum, but a dangerous engineer.
