We do not currently provide controls for slowing or speeding up the speaker tempo in Studio.
Our voices avatars are trained from the voices of real people, and they tend to take on the characteristics of those individuals, including speed.
We recommend auditioning the voice avatars to determine which voice meets your need for a faster or slower read. You may also adjust the speed via your preferred post-processing tool.
Tip: If you need to add pauses to the script, you can try adding punctuation such as commas, periods, hyphens, ellipses, or spaces between lines.