Central Bank Commentary, from Officials?

Hello,

Obviously with the economic calenders and stat sources finding global macro data is pretty easy. That being said some of the biggest impacts come from comments made by central banking officials, that are not scheduled or indicated or planned.

My question is what are the best sources to get these speeched or commentary before it is too late, and is there any way to prepare for them or be ready for them. Do any calenders list impending interviews or commentary sessions, beyond the scheduled central bank announcements.

Thanks in advance.