Axiom Audio 12" 500W Al. Coned sub, called the EpiCenter! Why, guess because in room response is flat to 18hz, easily handles the lowest pipe organ pedal tones, but surprisingly is very musical with great bass tonality and very low distortion. I have it low passed at 50 hz and my 2-way Ascend Acoustic Sierra-2EX monitors high passed at 50hz…combo is an Amazing blend of synergy and spacious 3D sound!! 
Ted
