There is no speed options there is no options other than the three other voices. Compared to the tts apps you can get on here, this one is worth no ones time.

requires selection of text, not compatible with sites that do not allow text selection/highlight

This is the only page-reading TTS that works for me (five-stars for that). FF 60.0.2. The only options I think the add-on needs for becoming five-stars are stop, pause, resume, speed up. An option to change voices would be a nice plus. Oh. The computer reader is way too dang slow for me. No way I read that slowly. Is brutal to listen to while following along. And unless other add-ons I have are conflicting there isn't a way to pause. If I get interrupted by someone walking into my office there isn't a way to politely pause and shift attention to the human. The add-on continues to drown them out unless I silence my speakers. But hey...at least the add-on works.