I am aware that there is not a bass and trebble function on this HU, but what is the easiest way to adjust these functions without sending the amp different frequencies?
There are no "bass treble" options. Hold down the "menu" button for a couple seconds and it will bring up the crossover. Press menu 2 more times until the EQ comes up and you can adjust the dfferent frequencies.
Pull it out. Switch it from 2-way to 3-way on the back. Plug your tweeter amp RCAs into the Front pre-outs, mid RCAs into the Rear pre-outs, sub amp RCAs into sub pre-outs and voila....you're now 3-way active. Hold down the menu button to adjust Xover points, EQ, Time Correction, etc.