American Presidents normally give televised speeches either from the Oval Office, or – as is often the case with the current President – in the cross hall. Brendan Greeley talked about some of the considerations that go into determining where the speech should be given:

• Presidents normally deliver bad news from the Oval Office. This is to indicate that they’re hard at work in the office, trying to resolve the issue.
• When a President gives a speech from the office, the cameras usually turn on to find the President sitting there. They were waiting for you.
• In contrast when giving speeches from the cross hall the cameras turn on to an empty hallway – and then the President walks out to the cameras. You are waiting for the President.
• The cross hall also allows the President to speak from a podium with a microphone rather than a mike at the chest. This allows viewers to catch background noises such as the room tone and the echo of the hall. It creates the atmosphere of a public appearance.
• President Obama, in particular, seems to like to present from the cross hall – possibly because he likes to gesticulate while he speaks and that’s difficult to do while sitting at a desk

Read more about Presidents who preferred set pieces, the first ever televised address, and what Sorkin might have to do with all of this over here.

Source: Businessweek