I have two MTX 12 Inch Terminators to replace my 15 inch's that i blew.?

The Terminator package came with amp, enclosure and subs and b knob, my question is i see on most amps there are a b filter and base boost and a power input knob on the amplifier but i cant find it on the amplifier. i Do see things you can turn but im not sure what they are there all abbreviated and i dont see any resemblance to a base boost knob or input knob any help? its a TNA251 MTX Terminator Cl D mono block amplifier.