I have never heard of any car stereo shop tuning a system "by ear". It's not the correct way to do it. I'd be willing to bet that if Tom bought Kicker audio equipment, that he has a multimeter. If not, you can get a decent one for $20-30. The link I posted earlier has the tones that you need to do the tuning. In fact, here is a link to it on another site. Cllick on the "Interactive Input Sensitivity (gain) Setting Tutorial". the second one down.
http://mobile.jlaudio.com/products_a...php?page_id=30
Find me a tutorial that says to set it by ear on JL or any other audio companys web site. Will most people be able to tell the difference. No. But, they also won't be able to hear the distortion in thier equipment that is causing it damage. Damage that will after time, cause failure.
Dale