Whenever I read discussions regarding speakers with a low sensitivity (e.g., 86 or 87 dB), people are always quick to make sure that the owner or potential buyer has an amp that is powerful enough to drive them. Since there are so many speakers out there with sensitivities rated at 91 dB or thereabouts, it begs the question to my mind of why manufacturers make speakers with low sensitivity ratings. I have not studied speaker design much at all, so I don't understand what might be gained by designing a speaker with a low sensitivity. There must be a reason why this is done. Help?