Cartesia Sonic-3.6
Cartesia’s flagship low-latency TTS for voice agents.
Model idsonic-3.6
Price$0.037 per 1K characters
Checked29 September 2026
Where it stands
31newer speech and audio models since its release
- NVIDIA Nemotron 3.5 Transcribe (30B-A4B)28 Oct 2026
- Hy-SimulMT-30B-A3B22 Oct 2026
- Eleven Realtime v1 Max / Mini20 Oct 2026
- Voxtral Mini Transcribe 3 (+ Mini Transcribe Realtime 3)20 Oct 2026
- Voxtral Small Transcribe 320 Oct 2026
The 5 newest are listed. All speech and audio models
- Before it from Cartesia
- Cartesia Ink-2 (streaming STT)9 Jul 2026
- Weights
- Closed weights; access is hosted only.
How to call it
3 ways to use Cartesia Sonic-3.6, with the model id each provider expects.
| Provider | Model id | Endpoint | Docs |
|---|---|---|---|
| Cartesia API | sonic-3.6 |
https://api.cartesia.ai/tts/bytes (also /tts/sse and WebSocket) |
docs.cartesia.ai |
| Cartesia API (pinned snapshot) | sonic-3.6-2026-08-27 |
https://api.cartesia.ai/tts/bytes |
|
| Web app | play.cartesia.ai |
Pricing
| Per 1K characters | $0.037 |
|---|
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: cartesia.ai, checked 29 September 2026.
Specs
- Input
- Text
- Output
- Audio
- Context window
- Not published
- Max output
- Not published
- Open weights
- No
- Licence
- Proprietary
- Released
- 27 August 2026
- Status
- Current
- Type
- Speech and audio
What stands out
What its maker marketed at launch, and what people found later, each with its source.
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.
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.
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.
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.
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).
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