I use this term loosely to cover everything from company boardrooms to political party conferences. You will see that there can be a vast difference in scale. In the boardroom it has become common to use gooseneck microphones or boundary effect microphones that are specifically designed for that purpose. This lies beyond what we normally consider to be sound engineering and is categorized in the specialist field of sound installation. The party conference is another matter. To achieve reasonably high sound levels the microphone has to be close to the mouth, yet the candidate – for obvious reasons – does not want to look like a microphone-swallowing rock star. Therefore the microphone has to be unobtrusive so that it can be placed fairly close to the mouth without drawing undue attention to itself (the cluster of broadcasters’ microphones in front of the lectern is another matter, but they don’t have to be so close). The AKG C747 is very suitable for this application.
You will have noticed that in this context microphones are often used in pairs. There are two schools of thought on this issue. One is that the microphones should point inwards from the front corners of the lectern. This allows the speaker to turn his or her head and still receive adequate pickup. Unfortunately, as the head moves, both microphones can pick up the sound while the sound source – the mouth – is moving towards one mic and away from the other. The Doppler effect comes into play and two slightly pitch shifted signals are momentarily mixed together. It sounds neither pleasant nor natural. The alternative approach is to mount both microphones centrally and use one as a backup. The speaker will learn, through not hearing their voice coming back through the PA system, that they can only turn so far before useful pickup is lost.
It is worth saying that in this situation, the person speaking must be able to hear their amplified voice at the right level. If their voice seems too loud, to them, they will instinctively back away from the mic. If they can’t hear their amplified voice they will assume the system isn’t working. I once saw the chairman of a large and prestigious organisation stand away from his microphone because he thought it wasn’t working. It had been, and at the right level for the audience. But unfortunately, apart from the front few rows, they were unable to hear a single unamplified word he said.