Is there a way to delay the start of wave 1 in survival?

[the guy thats not good]

I'm in the process of creating a survival map and i wanted to know if there was a way to delay the start of wave 1 until the player(s) activated a trigger or finished a set of dialogue.
*edit: i don't know much about creating maps in survival; what triggers the spawns of enemies and what defines the end of a wave?

[Gurt]

You as a map maker is in control of what happens in a survival map, when enemies spawn and when the round is over. See the tutorial section in the map editor for a brief explanation how to set up a survival map.