when I do the preshow spiel, because the theater is small or there is no standard house spiel, it's only done at house to half, or whatever point becomes the official "we are starting the show now" point.
normally it's been pretaped and is a sound Q, or I will do it over the god mic or (rarely, at one specific house) get up in front of the aud and announce, then head to the booth and start the show.
In larger houses, my experience has been the same but always on a pretape after the producer or his/her rep does their "give us money/subscribe" spiel and the show is about to start. The FOH staff takes care of calling the audience to their seats.
The only thing I give at 5 is to actors and crew, but I always coordinate that call with the house manager so we both know when my 5 and places calls happen, and she/he tells me when everyone (or almost) is in and I can start the show.