You can do whatever you like but I would connect the external 16ohm cab to the 16ohm amp output while kipping the internal 8ohm still connected. What "Kyle B" told you is totally correct, apart from showing a deep knowledge on that matter.I guess I could just disconnect the built in speaker and just run the extension can to be safe. The Budda has 4, 8, and 16 ohm taps
I asked because it's possible to easily rewire the 16 ohm cab to suit his needs.Doesn't matter how many speakers are in the extension cab. 16 ohm load is a 16 ohm load.