I'd agree with the above. Rated frequency response does not equate to what you get in all listening rooms. Besides the factor of the room, bass frequencies sum. So that if you had a speaker that really did measure 60hz from the listening position, setting the crossover at 60hz would result in a bass bump at around that frequency. In theory, you would want to set it a hair lower than where the bass drops off, however, the room is the most overlooked audio component.
