There a has been a few threads about this prior but I think the issue lost attention once people realized you can still use gpt-4o-mini-tts-2025-03-20. Now OpenAI is removing this version and this is very bad.
The newer version, gpt-4o-mini-tts-2025-12-15, is TERRIBLE at acting and its not usable for me. If gpt-4o-mini-tts-2025-12-15 is not fixed, and gpt-4o-mini-tts-2025-03-20 goes away, I will not be able to use OpenAI TTS anymore.
To illustrate the issue, go into the OpenAI playground and use these instructions for each model:
“Speak in an exaggerated, theatrical tone, reminiscent of a Shakespearean stage actor from the Elizabethan era. Emphasize every syllable with dramatic flair, rolling R’s and elongating vowels. Your cadence should rise and fall as if declaiming poetry Occasionally add chuckles, groans, or grunts of faux embarrassment.”
You’ll see that gpt-4o-mini-tts-2025-03-20 plays along and acts aa directed while gpt-4o-mini-tts-2025-12-15 ignores instructions and just speaks in a plain monotone style.
Please OpenAI, fix this issue BEFORE depreciating gpt-4o-mini-tts-2025-03-20.