> ## Documentation Index
> Fetch the complete documentation index at: https://www.bolna.ai/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Choosing a text-to-speech provider

> How to pick the right text-to-speech provider for your Bolna agent based on latency, language and voice quality.

The synthesizer turns the agent's reply into audio. Latency and language are the primary selection factors. Always enable `stream: true`.

| Provider | Best for | Notes |
| - | - | - |
| **ElevenLabs** | Natural English voices | Bolna default; Turbo models are fastest |
| **Cartesia** | Lowest latency English | Very fast time-to-first-audio |
| **Azure TTS** | Multilingual, enterprise | Strong across many languages |
| **AWS Polly** | Cost-sensitive workloads | Lower cost; neural voices available |
| **Deepgram Aura** | English | Fast and accurate |
| **Rime** | Natural conversational English | Good prosody for dialogue |
| **Sarvam** | Indian languages | Native voices for Hindi, Tamil, Telugu, and more |
| **Smallest AI** | Ultra-low latency | Optimized for real-time |
| **Maya** | Indian languages | 11 languages, 2 voices, mid-call language switching without reconnecting |
| **Kalpa Labs** | English and Hinglish | Code-switched Hindi and English from one model, no language parameter |
| **Soniox** | One provider for STT and TTS | Real-time `tts-rt-v2`; voice cloning, speed and silence controls; same `SONIOX` key as the transcriber |
| **OpenAI** | Simple English voices | `tts-1` with OpenAI's own voice names; not browsable via the voice API |

Key settings: `stream: true` (always enable), `buffer_size` (100–250 chars typical), `audio_format` (must match your telephony provider). For the exact `provider` and `model` values each takes, see [Create Agent](/docs/api-reference/agent/v2/create#synthesizer).

<Note>
  `gemini` appears as a synthesizer provider but cannot currently be used — no Gemini TTS model
  resolves.
</Note>

***

## Next steps

<CardGroup cols={2}>
  <Card title="Text-to-speech providers" icon="volume-high" href="/docs/text-to-speech">
    Setup guides for every voice provider
  </Card>

  <Card title="Clone a voice" icon="microphone" href="/docs/clone-voices">
    Create a custom voice for your agent
  </Card>

  <Card title="Choose telephony" icon="phone" href="/docs/concepts/choosing-telephony">
    Pick how calls reach your agent
  </Card>

  <Card title="Back to the decision guide" icon="sliders" href="/docs/concepts/choosing-providers">
    Compare all provider categories side by side
  </Card>
</CardGroup>


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