I was reading a thread somewhere asking which way to lay an amp down when transporting it. Ted Weber had told someone and was quoted to say the amp should be transported with the face down (magnet up). The reason being if it's the other way the speaker will be bumped to move in an unnatural way that can potentially damage the speaker. I understood it to mean the speaker cone is not designed to move very far back into the basket (towards the magnet) but is designed to move out of the basket or away from the magnet. So I am taking this info and applying it to the idea of laying the speaker face up (the way Ted Weber said not to transport it) as potentially being bad for it. Maybe, maybe not...Why would it be hard on the speaker?
OR make sure there is none of your guitar in the monitors. Like either or. This avoids mutliple out of phase sources of the same sound (which makes for comb filtering and general muddiness making you not able to hear what you are playing.This and bring your amp volume to as low as you can.