You need to connect the L/R master output of the G65 to the AC12, then the Master output of the AC12 to the Master Speaker. Then S lead between the speakers and crucially S lead from the slave speaker out to the slave comms socket of the AC12. This last connection makes Slave comms available at the slave outputs of the G65.

For the centre you then need to use the slave output C/S to a second AC12. You also need a special master cable to connect the AC12 to the Centre https://www.Meridian-audio.info/public/ac12_-_m5_lead_modification%5b3085%5d.jpg if you want the centre to also supply comms to a sub. There is no need to connect slave comms back to this AC12.

Alternatively you can ignore comms on the second AC12 entirely and use an S lead from the slave L/R to the Centre comms in and then return the centre comms out to the FIRST AC12 with another S lead.

From what you wrote, I think just making the slave comms return from your slave L/R to the first AC12 will fix your issue.

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