Sonic key stats
- Latency (measured)
- 116 ms1
- Vapi streaming benchmark (50 trials per model) (checked 2026-06-10) Median of 50 sequential live streaming trials, June 2026; includes network RTT from the benchmark machine.
- docs.cartesia.ai/build-with-cartesia/tts-models/latest (checked 2026-06-10)
- cartesia.ai/pricing (checked 2026-10-26) The displayed $50 per 1M characters is the effective rate of Pro included credits ($5/month for 100K), assuming full use, rather than an overage rate. Startup included credits are about $39.20/1M ($49 for 1.25M); Scale about $37.38/1M ($299 for 8M). Overages cost $65/$45/$38 per 1M credits on Pro/Startup/Scale. TTS uses approximately 1 credit per character; preprocessing can affect usage (docs.cartesia.ai/pricing). Professional voice clones require Startup or higher; custom Enterprise rates may differ.
- cartesia.ai/blog/sonic (checked 2026-06-10)
Background
Sonic was Cartesia's debut voice model, released in May 2024 as the first text to speech engine built on the state space model architecture its founders pioneered in academia. At launch it generated lifelike speech with 135 ms model latency, the fastest in its class at the time, with instant voice cloning and speed and emotion controls. Four newer Sonic generations have since superseded it, but it remains the baseline that started Cartesia's run at real time voice.
Sources: cartesia.ai
At a glance
The first SSM voice model, with instant cloning and 15 languages. In our 50 trial streaming benchmark it returned first audio in a median of 116 ms, still among the fastest results on the Index.
Sources: docs.cartesia.ai
Frequently asked questions
- How is Sonic tested on the Humanness Index™?
- Listeners hear Sonic against another model in a blind head to head round, both voices reading the same customer support prompt from the same cloned source voice, and they pick whichever sounds more human. Its Humanness score derives purely from those votes.
- Is Sonic still Cartesia's current model?
- No. Four newer generations have superseded it, with Sonic 3.6 as the current flagship. Sonic remains in the arena as the baseline of the family.
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