So I've been watching a lot of those Mix With the Masters videos that show how famous guys mix, and they're mixing with speakers, talking while they mix, yet there's no playback bleed when they're speaking. How do they achieve that?

For comparison I've mixed several live shows where the vocalist's mic caught a lot of bleed from the band, and even when I gated the bleed, I could still hear it in the parts where the vocalist sings (particularly those nasty mono cymbals that really stick out when you're adding highs to the vocalist).

 

This is more about mixing than sounds, so I'll move it to mixing and mastering, you'll have better answers there.