I feel like I'm approaching this problem from the opposite direction from many on the interwebs. I don't care very much about speaker quality. I spend most of the day in voip calls in Google Hangouts and Skype. All of my team mates use wired headsets and their microphone audio quality is superb. I am trying out a bluetooth headset for the 10th time in 5 years (because I keep hoping it will get better), and the microphone quality sucks SO bad that I'm probably going to end up taking this headset back (again).
This has been a problem for various bt headsets I've used, but for the sake of providing all possible information: I'm using a Plantronics Voyager.
Audio file links borrowed from this su question.