What hurts a speaker?

Yawning and falling asleep is very insulting to a speaker. Also having a conversation with someone can also be a bit offensive to a speaker. Showing up late, and/or leaving before the speaker finishes is rude to a speaker. And never mock or make fun of a speaker.

You are most likely to notice a problem with your speaker after getting a demo of your buddy's new kilobuck set up.
This can be corrected by spending an equal amount of money yourself.

A chain saw.

Being mentioned in the same sentence as Bose.

UPS!!!