let·down /ˈlɛtˌdaʊn/
–noun
1. a decrease in volume, force, energy, etc.: a letdown in sales; a general letdown of social barriers.
2. disillusionment, discouragement, or disappointment: The job was a letdown.
3. depression; deflation: He felt a terrible letdown at the end of the play.
4. the accelerated movement of milk into the mammary glands of lactating mammals upon stimulation, as by massage or suckling.
5. Aeronautics . the descent of an aircraft from a higher to a lower altitude preparatory to making an approach and landing or to making a target run or the like.
Wasn's as good as the first one, or the previous series.