The only English language Synth V voice available is Eleanor Forte. (Honestly, I think she sounds very American to me.) When you type words with her, you can change the phonemes to tweak the pronunciation if you aren't happy with the default pronunciation. (If it helps, I made a color coded Synth V phoneme chart that you can reference, you have to click DOWNLOAD in the upper right corner to see it.)
This is the page in the Synth V manual on how to change phonemes: Editing Phonemes
I like to use Cambridge Dictionary: Find Definitions, Meanings & Translations to look up the American pronunciation of words, it shows the IPA symbols, but the chart I made contains a column for IPA symbols so you don't get confused.
This is the page in the Synth V manual on how to change phonemes: Editing Phonemes
I like to use Cambridge Dictionary: Find Definitions, Meanings & Translations to look up the American pronunciation of words, it shows the IPA symbols, but the chart I made contains a column for IPA symbols so you don't get confused.