Gemini 2.5 Flash TTS | EmpirioLabs AI Docs

Google · Audio Generation

POST /v1/audio/speech

Low-latency text-to-speech with single- and multi-speaker voices and controllable style, accent, and expressive tone for production apps.

At a glance

Field	Value
Model id	`gemini-2-5-flash-tts`
Input modalities	Text
Output modalities	Audio
Context window	-
Weight precision	-
Features	-
Native inference	No
New	No
Supported endpoints	`POST /v1/audio/speech`

Pricing

Charge	Spec	Rate
Input	per 1M prompt tokens	$1.50
Output	per 1M generated tokens	$30.00

Example request

$ curl https://api.empiriolabs.ai/v1/audio/speech \
>   -H 'Authorization: Bearer $EMPIRIOLABS_API_KEY' \
>   -H 'Content-Type: application/json' \
>   -d '{"model": "gemini-2-5-flash-tts", "input": "Hello from EmpirioLabs."}'

Parameters

Parameter	Type	Required	Default	Description
`input`	string	yes	-	Text to convert to speech. For multi-speaker mode, prefix lines with Speaker1: / Speaker2:.
`mode`	enum	no	`"single"`	single = one voice, multi = two-voice dialogue (uses voice + voice2 + speaker names). · Allowed: `single`, `multi`
`language`	string	no	`"en-US"`	BCP-47 language tag (en-US, es-ES, etc.) for pronunciation cues.
`voice`	enum	no	`"Charon"`	Primary voice name (e.g. Kore, Puck, Aoede). Leave blank for the default. · Allowed: `Zephyr`, `Puck`, `Charon`, `Kore`, `Fenrir`, `Leda`, `Orus`, `Aoede`, `Callirrhoe`, `Autonoe`, `Enceladus`, `Iapetus`, `Umbriel`, `Algieba`, `Despina`, `Erinome`, `Algenib`, `Rasalgethi`, `Laomedeia`, `Achernar`, `Alnilam`, `Schedar`, `Gacrux`, `Pulcherrima`, `Achird`, `Zubenelgenubi`, `Vindemiatrix`, `Sadachbia`, `Sadaltager`, `Sulafat`
`voice2`	enum	no	`"Kore"`	Second voice name for multi-speaker mode. · Allowed: `Zephyr`, `Puck`, `Charon`, `Kore`, `Fenrir`, `Leda`, `Orus`, `Aoede`, `Callirrhoe`, `Autonoe`, `Enceladus`, `Iapetus`, `Umbriel`, `Algieba`, `Despina`, `Erinome`, `Algenib`, `Rasalgethi`, `Laomedeia`, `Achernar`, `Alnilam`, `Schedar`, `Gacrux`, `Pulcherrima`, `Achird`, `Zubenelgenubi`, `Vindemiatrix`, `Sadachbia`, `Sadaltager`, `Sulafat`
`speaker1_name`	string	no	`"Speaker1"`	Display name used in the input prefix for speaker 1 (default: Speaker1).
`speaker2_name`	string	no	`"Speaker2"`	Display name used in the input prefix for speaker 2 (default: Speaker2).
`output_format`	enum	no	`"WAV"`	Audio file format (mp3, wav, opus, flac, etc.). · Allowed: `WAV`, `MP3`, `OGG`, `ALAW`, `MULAW`
`speed`	number	no	`1.0`	Playback rate. 1.0 = natural; <1 slower, >1 faster. · Range: 0.25 – 2.0
`volume_gain`	number	no	`0`	Output gain in dB. 0 = unchanged. · Range: -96 – 16
`sample_rate`	enum	no	`"24000"`	Output sample rate in Hz (8000, 16000, 24000, 44100, 48000). · Allowed: `8000`, `16000`, `22050`, `24000`, `44100`, `48000`
`style_prompt`	string	no	-	Natural-language style direction (e.g. “warm, conversational” or “newscaster, serious”).

Notes

Modes

Single speaker
Multi-speaker (max 2 voices) — text must be in SpeakerName: text format

Limits

Text + style prompt: 4,000 bytes each
Audio billing: ~32 tokens per second of generated audio (~10-15 chars/s)

Voices and languages

30+ voice options across emotional/tonal characters
24+ language locales supported

Output formats

MP3, WAV, OGG

Machine-readable schema: GET https://api.empiriolabs.ai/v1/models/gemini-2-5-flash-tts.