The Speech player allows you to generate audio output using the speech synthesizer of Mac OS X, whose job is to speak out a text you enter using an adjustable synthesized voice. The Speech player is similar to the audio input player in that it is not linked to the fader, but can be used for room placement.
It is located in the lower part of the main window:
You can enter a text, usually a few words, in the text to speak field, and then click the "say" button to make Speech speak out this text. If you hold the option or control key while clicking the "say" button, the text will be repeated until you click the button again. You can select one of the synthesized Speech voices that come with Mac OS X in the voices menu.
The four sliders in the Speech player's lower part are audio paramters that work just like the ones on the audio file players.