Type
Spec
Rate
Synthesis
per 10,000 characters
$0.14
StepAudio 3 TTS and Gemini 2.5 Pro TTS side by side: specs, capabilities, parameters, and live pricing from the EmpirioLabs catalog.
StepFun 
Google Audio GenerationStepAudio 3 TTS from StepFun and Gemini 2.5 Pro TTS from Google are both in the Audio Generation category, available through the EmpirioLabs API.
| Spec | StepAudio 3 TTS | Gemini 2.5 Pro TTS |
|---|---|---|
| Model ID | stepaudio-3-tts | gemini-2-5-pro-tts |
| Author | StepFun | |
| Released | Sep 9, 2026 | May 20, 2025 |
| Max output | - | 19,661 tokens |
| Input | Text | Text |
| Output | Audio | Audio |
| Region | International | - |
| Endpoints | POST /v1/audio/speech POST /v1/audio/speech:stream | POST /v1/audio/speech |
| Capabilities |
Live rates from the EmpirioLabs catalog for both models. Each rate card always matches what the API charges.
Request parameters each model lists on EmpirioLabs, with the allowed values or range where one applies. A dash marks a parameter the model does not list.
| Parameter | StepAudio 3 TTS | Gemini 2.5 Pro TTS |
|---|---|---|
| input | max 1000 | string |
| voice | lively-girl, vibrant-youth, soft-spoken-gentleman, magnetic-v... Default: lively-girl | Zephyr, Puck, Charon, Kore, Fenrir, Leda, Orus, Aoede, Callir... Default: Charon |
| instruction | max 500 | - |
| speed | 0.5 to 2 Default: 1 | 0.25 to 2 Default: 1 |
| volume | 0.1 to 2 Default: 1 | - |
| language | en, zh, ja, ko, fr, es Default: en | string Default: en-US |
| response_format | mp3, wav, flac, opus, pcm Default: mp3 | - |
| sample_rate | 8000, 16000, 22050, 24000 Default: 24000 | 8000, 16000, 22050, 24000, 44100, 48000 Default: 24000 |
| markdown_filter | boolean Default: false | - |
| pronunciation_map | string | - |
| mode | - | single, multi Default: single |
| voice2 | - | Zephyr, Puck, Charon, Kore, Fenrir, Leda, Orus, Aoede, Callir... Default: Kore |
| speaker1_name | - | string Default: Speaker1 |
| speaker2_name | - | string Default: Speaker2 |
| output_format | - | WAV, MP3, OGG, ALAW, MULAW Default: WAV |
| volume_gain | - | -96 to 16 Default: 0 |
Maximum input is 1,000 characters. Content in parentheses is treated as delivery direction and is not spoken. Use instruction for global emotion or style guidance, up to 500 characters. Twelve system voices are available. Recognized languages are Chinese, English, Japanese, Korean, French, and Spanish, with languages other than Chinese and English in preview. Output formats are mp3, wav, flac, opus, and pcm at 8000, 16000, 22050, or 24000 Hz. Wav is returned as a complete file rather than streamed. This model does not support voice_label.
StepAudio 3 TTS serves speech through POST /v1/audio/speech and returns playable audio. Send the text to speak as input with the model id stepaudio-3-tts. Both models are called through the same endpoint. Set model to stepaudio-3-tts or gemini-2-5-pro-tts. Get an API key from the EmpirioLabs dashboard.
curl https://api.empiriolabs.ai/v1/audio/speech \
-H "Authorization: Bearer $EMPIRIOLABS_API_KEY" \
-H "Content-Type: application/json" \
-d '{
"model": "stepaudio-3-tts",
"input": "Welcome to EmpirioLabs. Your build just finished."
}' \
--output speech.mp3Prompt tests and comparison runs that cover both models.
StepAudio 3 TTS is the newer release (Sep 9, 2026); Gemini 2.5 Pro TTS was released on May 20, 2025. Capabilities listed only for StepAudio 3 TTS: contextual tts, voice control. Capabilities listed only for Gemini 2.5 Pro TTS: multi speaker. The specs, rate cards, and parameters on this page come from the live EmpirioLabs catalog.
StepAudio 3 TTS is the newer release (Sep 9, 2026); Gemini 2.5 Pro TTS was released on May 20, 2025.
The two models are priced on different units or tiers, so compare the live rate cards on this page. They always match what the API charges.
Yes. Both models use POST /v1/audio/speech with the same EmpirioLabs API key, so most integrations switch by changing the model value. Check the parameters table on this page first if you rely on a model-specific parameter.
Yes. Open each model in the EmpirioLabs playground and run the same prompt on both, with the parameters the API exposes.
Check out our pricing or reach out if you want your own model deployed on our stack.
