David, the language in the online EP500 manual is to the effect that the bypass setting is equivalent to a 150Hz "crossover"(actually just a low-pass). This indicates that the previous 100Hz "brickwall" filter apparently was moved to 150Hz on later EP500s. Because of the presence of the brickwall filter there actually never was a complete "bypass", since that filter was always there(previously effective at 100Hz), and I suppose that there's no purpose in using the term.

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Enjoy the music, not the equipment.