How to shut off external speakers connected to Imac optical port?

[mattg3]

I own an old Imac still running OSX 10.6.8. Im about connect powered speakers to my imac headphone out port using optical option.These speakers are in another room and I only want to send itunes music to them.Any way to shut them off using Imac settings so when im on the computer my audio comes through Imac and not the external speakers in the other room? thanks

 

[roadkill401]

The foolproof method is to pull the small plug out from the back of the iMac and then the speakers inside your iMac will come to life.