What's the minimum battery voltage should I expect before my speaker starts to crackle?

[baldusi]

3.7v batteries vs 7.4v batteries: pros and cons?

It seems like 3.7v batteries are far more popular than 7.4v batteries, and I’m curious why? At first blush, from a place of ignorance, it would seem that if we need to have a given voltage to drive various components, starting from 7.4v would provide more useful life that starting at 3.7v would, for a given amp-hour rating. Is this not the case? Are there other reasons to choose one over the other? Thanks