Recording gang vocals

How do you guys usually monitor for the guys recording the gang vocals, for example if you're recording 10 people, you can't exactly give them all headphones. I heard of the use two speakers on each side of the room with inverted phase, but have never tried this in practice. Any other ideas?

How long are the parts? Do they need a pitch reference? If short/no was your answer, you can toss a pair of headphones on the ground, crank the shit out of them so they can hear the click/lead in, and then drop the volume before they all do the part.

I do this when tracking vocals sometimes as a way to let the vocalist be in the same room and not have to be wearing headphones; he wears headphones, I manually duck the volume around his takes. Bleed goes away and my ears don't get sore and sweaty.
 
How do you guys usually monitor for the guys recording the gang vocals, for example if you're recording 10 people, you can't exactly give them all headphones. I heard of the use two speakers on each side of the room with inverted phase, but have never tried this in practice. Any other ideas?

Use one person as the director/coordinator. They wear the headphones and will count the part in, do the waynes world thing and dont say 2 or 1. lol
 
I went ahead and recorded 4 guys at once, took a few takes, as mentioned above, if they're poorly rehearsed its difficult. did a couple of takes then got them to switch positions then recorded another couple of takes to layer it up nicely.