The routing for this costs you an aux and the use of the delay as an effect, but it's really handy.
Send everything at unity, post fader, to the delay. Set the delay to 0 regen and whatever delay time you want. Send only the delay, pre fader, to an unused aux. That aux output feeds the back of the room.
My default aux setup is 1-4 mons, 5 delay, and 6 subs.