I have 7 pairs of speakers run thru a speaker selector (impedance matching) then into my Onkyo TX8511. The receiver is set at 8 OHMs. When I have a CD on the receiver frequently goes in and out of protect mode. Any ideas?
Re-check all your wiring. I would do this one speaker at a time. Specifically, disconnect all the speakers, then reattach one at a time. Replay your CD at the volumes you had where you experienced the problem.
While it could just be you're pushing your receiver too far, you may just have a single strand of wire touching one of the terminals! (Or that your speaker selector is doing it)
If you're using wiring directly to binding posts, be sure to rebind the wire on EACH post (including at the speakers). If you have banana plugs, do the same... redo the connections.
Inspect, inspect, inspect.
If it's not the speaker selector nor the wiring... could just be the receiver. But, before blaming the receiver, check the wiring and rule-out the selector.