Make the story and structure easy to grasp, even if the details are complex

Most audiences contain people of varying familiarity with your specialty. Should the speaker generalize the talk so everyone can understand? If so, you might lose people who can best comment on your work. Conversely, if you gear the talk to the specialists, you may lose a sizable part of your audience.

Obviously the speaker needs to first decide who they care about, but it is possible to at least broaden the range of audiences that might get something out of your talk. Quite simply, the story and structure should be make accessible even if the details and methods are not. Figure out the least expert type of person you want to communicate with and be sure that your overarching question and outline are comprehensible to that individual. It's OK if they can't comprehend a few of the slides that provide supporting data, just take a few seconds and try to summarize their meaning for the bigger picture.

There are limitations. A methodological talk on quantum electrodynamics probably cannot be made comprehensible to an English major. However you can broaden the target audience by learning to deliver you overall message in a simple manner to the least expert person you care about reaching.