it stops your subs from attempting to play higher frequencies. Setting at 80hz the power is concentrated in the 20-80hz range. Set to "thru" it will play from 20hz - whatever the subs natural roll off is (sometimes 150-300hz) and that can damage coils by creating heat with no motion.

Done! Thanks! Did not realize this. So basically limiting the sub to a max of 80hz for the high end, I did not know.

80hz is the low E string on a regularily tuned guitar, 160hz is the E played on the 7th fret of the A string... If I was going to listen to a band I would want to hear 80hz as much as I would want to hear 40 and 160

what are you talking about.... He will still hear 40, 80, & 160hz....

His sub will play 20 - 80hz, and his mids will pick up from 80hz up... I don't see the problem.

I have a low pass filter on my kicker amp