I am passing the correct speed value to the API but it is being ignored. The voices always play back at the default speed regardless of which speed value is specified. This appears to only be an issue with the gpt-4o-mini-tts and not tts-1

Update: The speed parameter is not supported for gpt-4o-mini-tts currently. This was a bug in our documentation which has been updated. Thanks again for flagging this!

New TTS model (gpt-4o-mini-tts) Ignoring Speed parameter

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bret1 June 24, 2025, 8:12pm 14

It seems you are incorrect. I tried the new model again recently and it is no longer ignoring the speed parameter. So apparently it is indeed supported?

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New TTS model (gpt-4o-mini-tts) Ignoring Speed parameter

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