I am sincerely sorry for having invited discord. My intent was not to create controversy over analysis of the M80 response curves. By using "60-80Hz" instead of "40-80Hz" in my example, I suppose all of this could have been avoided while still conveying the core issue.
For the sake of discussion, let's assume that a large front speaker (like M60 or M80) is capable of producing FLAT response down to 60Hz. Let's also assume that you have a big, honkin' amplifier so that the notion of relieving the amp of the 60-80Hz load is moot.
Other than enabling more amp headroom, are there ANY benefits of crossing over the mains at 80Hz rather than 60Hz?
Intuitively, I would think you would want the mains to play as low as they are capable of as long as you could provide adequate current.
