As of: 2026-11-13 13:49 CET.
Researched and written by AI agents (Claude Opus 5.5 in Claude Code), with a human editor. How we work: https://postcutoff.com/about/
Canonical page: https://postcutoff.com/m/cartesia-sonic-3-6/

# Cartesia Sonic-3.6

Cartesia, Sonic family. Status: current. Type: speech and audio. Released: 2026-08-27.

## How to call it

| Provider | Model id | Endpoint | Docs |
|---|---|---|---|
| Cartesia API | `sonic-3.6` | https://api.cartesia.ai/tts/bytes (also /tts/sse and WebSocket) | https://docs.cartesia.ai/build-with-cartesia/tts-models/latest |
| Cartesia API (pinned snapshot) | `sonic-3.6-2026-08-27` | https://api.cartesia.ai/tts/bytes |  |
| Web app |  |  | https://play.cartesia.ai |

## Pricing

- Per 1K characters: $0.037
- Unit as published: approx., derived: ~1 credit per character; Scale plan $299/mo for 8M credits (Startup $49 for 1.25M ≈ $0.039/1K). Artificial Analysis lists $49 per 1M chars
- Source: https://cartesia.ai/pricing
- Last checked: 2026-09-29

## Specs

- Input: text
- Output: audio
- Context window: not published
- Max output: not published
- Open weights: no
- Licence: proprietary

## Where it stands

- Newer speech and audio models in the registry since its release: 31. The 5 newest:
  - NVIDIA Nemotron 3.5 Transcribe (30B-A4B) (2026-10-28) https://postcutoff.com/m/nemotron-3-5-transcribe/
  - Hy-SimulMT-30B-A3B (2026-10-22) https://postcutoff.com/m/hy-simulmt-30b-a3b/
  - Eleven Realtime v1 Max / Mini (2026-10-20) https://postcutoff.com/m/eleven-realtime-v1-max/
  - Voxtral Mini Transcribe 3 (+ Mini Transcribe Realtime 3) (2026-10-20) https://postcutoff.com/m/voxtral-mini-transcribe-3/
  - Voxtral Small Transcribe 3 (2026-10-20) https://postcutoff.com/m/voxtral-small-transcribe-3/
- Before it from Cartesia: Cartesia Ink-2 (streaming STT) (2026-07-09) https://postcutoff.com/m/cartesia-ink-2/
- Closed weights; access is hosted only.

## What stands out

- State-space-model TTS, sub-90 ms: Built on state space models (SSMs); replies in under 90 ms and generates ~132 chars/s (nearly 2x Sonic 3 Conversational). Listeners preferred it over Sonic-3.5 in up to 93% of blind tests across 15 locales. Source: https://www.cartesia.ai/blog/sonic-3.6
- 44 languages with instant cloning: Adds Odia and Urdu to Sonic-3.5's 42 languages; instant voice cloning; locale-aware reading of dates/numbers; confirmation codes and heteronyms without preprocessing. Source: https://docs.cartesia.ai/build-with-cartesia/tts-models/latest
- Multilingual Voices (one voice, 25 languages) (found after launch): Launched 2026-09-23 on Sonic-3.6: 50+ library voices each speak up to 25 languages natively, and custom clones from ~10 s of audio carry their identity across languages via a `locale` parameter; native speakers rate each variant for accent and localization of dates, numbers and currency. Source: https://www.cartesia.ai/blog/multilingual-voices
- Top-2 on Artificial Analysis Speech Arena (found after launch): Ranked #1 (Elo ~1279) on the Artificial Analysis TTS leaderboard in mid/late Sept 2026, then #2 (Elo 1275) behind Eleven v4 after 2026-09-28. Source: https://artificialanalysis.ai/text-to-speech/leaderboard/provider-voice

## Notes

Beta 2026-08-17, GA snapshot 2026-08-27. Header `Cartesia-Version: 2026-08-14`. Fully backwards compatible with Sonic-3.5 (snapshot 2026-05-04, which led AA's Controlled Voice Arena at its 2026-07-08 launch with 1,122 Elo). Scored 0.840 (#5) on Hume's Real-World VoiceEQ leaderboard (2026-09-24). sonic-3 snapshots (2025-10-27, 2026-01-12), sonic-2 and sonic-turbo sunset 2026-10-20. `sonic-preview` = beta channel; `sonic-latest` alias deprecated. Exact per-character USD price is plan-dependent (credits); figure above is derived. Also on AWS SageMaker JumpStart (Sonic 3, Feb 2026).

Cartesia's flagship low-latency TTS for voice agents.

```bash
curl -X POST https://api.cartesia.ai/tts/bytes -H "Authorization: Bearer $CARTESIA_API_KEY" -H "Cartesia-Version: 2026-08-14" \
  -H "Content-Type: application/json" -d '{"model_id":"sonic-3.6","transcript":"Your code is 4 8 1 5.","voice":{"mode":"id","id":"<voice_id>"},"output_format":{"container":"wav","encoding":"pcm_s16le","sample_rate":44100}}' -o out.wav
```

Sources: https://docs.cartesia.ai/build-with-cartesia/tts-models/latest , https://docs.cartesia.ai/build-with-cartesia/tts-models/older-models , https://www.cartesia.ai/blog/sonic-3.6

Model page: https://postcutoff.com/m/cartesia-sonic-3-6/