I know nothing about Crowns but I would just play it safe and plug in some speakers before relying 100% on the phone jack muting them. I would assume
that they don't. Better to be safe than sorry so you should keep the power down and adjust gradual.
I know on my Gigrack 1000 they don't mute the speakers so I would think they would on the Crown.
Well, I would think a soundman should be listening to what's coming out of the mains, because that's what he's adjusting.
And if the phones used a different voulume control, I could maybe see it. The way it is, it seems to me like it would be an either/or situation, but you can't do that.
Besides, I don't know of too many acts that have a soundman using a 50w/channel amp.
Now I suppose I gotta start looking at those routing things, like a Central Station. Not what I wanted to spend my fun money on.