I have the 1501D and I am using telephone wire and a bass know from an old rockford fosgate 801S. The annoying thing is I have to turn it counter clockwise to turn up the bass. On this subject, does the bass knob effect overall gain, or boost at 40Hz? The manual says the thunder EQ adds up to 18db at 40hz, but says the EBC 2 external bass control will alow the bass level to be adjusted to overcome noise and other interference. I always assumed it was a gain control. By the way, I have the old 2003 model. I don't see the harm in having a bass knob as long as you flat line your EQ's before adding boost.