Mixing Speaker Impedance?

If there's only one switch than select for the lowest impedance.

Wont setting the amp to 4 ohms limit speakers with 8 ohm requirements?

"08-28-13: Azag
Wont setting the amp to 4 ohms limit speakers with 8 ohm requirements?"

It shouldn't because you will be setting the volume levels for each speaker when you do the setup with your preamp. The only other question is to weather the amp has enough power do drive the speakers. MA is not a difficult speaker to drive. I can't imagine either of your 2 choices not working.

The switch is for the amps protection so that it doesn’t get too hot.

Wont setting the amp to 4 ohms limit speakers with 8 ohm requirements?

This setting limits the amp, since it alters the operation of the amp to run cooler, that typically results in less power output capability. The 4 ohm speaker requires the most power, with the 6 ohm being less, and the 8 ohm less than that. Also, the size room and how loud you play the system are factors. Obviously, louder volume and larger rooms require more power. In a way this may not make sense, but as I said, it is to protect the amp, by limiting its output to stay cooler. Ideally it is best use a 4 ohm rated amp with 4 ohm speakers.

Just curious as to the choice of a 9 channel amp for 5 speakers, if you don’t need the extra channels, why not get a 4 ohm rated 5 channel amp?

If you have extra channels, try doing a vertical biamp. It may sound a lot better.