I just recently purchased a GK 700RB/210 combo. It says in the manual to obtain growl from the woofer speakers to increase the Boost knob while turning down the Woofer Master Volume. I tried this, but the sound coming from the speakers was just as clean as setting the Woofer Master Volume higher and the Boost knob lower! It also seems as though it's impossible to overdrive the Pregain Control. Where's the growl?