I have validated by amplifier design and I have good results when I test it with load resistors. When I connect it to my speakers and play program material or a test sweep at high power, the amplifier occasionally shuts down. I have confirmed that it is an over-current shutdown. Why can I drive resistors but not a speaker of similar rated impedance?
ANSWER: What you are probably experiencing is the fact that many/most change their impedance with frequency. For example, a 4 Ohm speaker may have an impedance of less than 2 Ohms somewhere in the audio band. You can confirm the behavior of your speaker by creating a test loop with the speaker (only) and your audio analyzer and measure its impedance in the audio band. It may turn out to have an unstable impedance vs frequency characteristic and causet this problem. If you are designing a "closed system" (IE: shipping speakers as a part of your final product), you can ask your speaker vendor to improve his speaker.