Since you say hearing problems aren't the issue, Vick, I want to use this opportunity to speculate about whether there might be an inter-cultural competency issue involved here --
especially since you write 'have to be huddled together'.
During a Vatican tour, our guide (who was using the headphones system anyway) kept admonishing us at the start to stop being so non-Italian, meaning we should rub shoulders and assert ourselves to get by the others in the crowd. Most people (WASPy people) had to be reminded over and over, and it still didn't work -- they lagged behind as the guide moved to the next stop, left a respectful distance and strolled casually, which meant that they were separated and lost from the peloton at every turn.
If you're on the tour, part of the group, why would you not huddle together and look directly at the guide you hired? Are you on the tour or aren't you?
This is like people who go to the movies and sit in the back -- they like the cinema, it seems, but they don't actually care about what's going on onscreen very much. They're there for other reasons. Social drinkers only, you might say :-).
I should add that I have dabbled in docenting in my day, and when being trained, we are usually told to move briskly between stops but not to scold the listeners about keeping up with you too much, because people don't like to be scolded. People who really want to hear the guide will stick beside the guide. People who are just along for the ride can catch the gist.
This viewpoint is also a little lacking in cultural sensitivity -- many people are following a model or rubric in their heads that includes rules about social distance and personal space and deference to authority, and it expresses itself in ways that make keeping a tour group together and on track difficult.
Also, every group has people operating according to different models and interested in different objectives. I stick right beside the speaker, and like to chat him or her up while moving between stops. Some people in the group want to meet other people in the group for a variety of social reasons. Some people in the group want to get photos of the textile patterns on the window trimmings. Or whatever. It's a small miracle that you ever get to all the points you intended and that most everyone is happy at the end.
To keep from running on, let me just emphasize that if you step back and consider the social assumptions you're following, you might find that adjusting them to the tour situation may help you be better positioned to hear and enjoy the narration, by keeping up with the narrator and helping him or her keep the tour flowing and together.