Even 11 + volts is not good for your amps. If this is with your car running then your alterantor or battery may be bad. Your amps allong with your computer at high volume may be drawing much current for your batt / alternator to handle. At that volume your car may be providing to little voltage and your amps go into protect. But since your computer has a larger voltage range the computer continues to run. If your car was off for those reading try running it and do the same test but also monitor the voltage at the amps at high volume just below the known volume limit and see how low they are. IF the voltage is low your battery or alternator may be going out and may need a new one. Give that a try and ghood luck.