It's not really about speed, it's about rhythm, density, presentation style, and audience. When I was in competitive public speaking and debate, I spoke at abo

It's not really about speed, it's about rhythm, density, presentation style, and audience. When I was in competitive public speaking and debate, I spoke at about 200 wpm. However, those speeches were all pre-scripted to the letter, so I had control over the density and presentation. I could script a rhythm of speech that allowed an audience to keep up without feeling overtasked. When I presented from notes, like in debate, or like a presentation such as the author was giving, I spoke a little slower because I had to "choreograph" the rhythm and density on the fly. And obviously, it really depends on your audience. This is sorta a given, but the more knowledgeable they are, the denser your presentation can be. Obviously you still need a good rhythm, else you'll lose the audience. The purpose of a speaking rhythm is almost like a mental slide that you are constructing over the course of the talk. You want it to be smooth and to take the audience where you want them to be. There are no problems with going down the slide at speed. But if you have no rhythm, it's like putting bumps and corners in it. So basically your speed doesn't matter (within reason) if you have the other elements down. But if you are struggling with the elements of communication, yes, slowing down will "solve" the issue.