Overview

The latency leader. Built on state space models, Cartesia’s Sonic streams speech in ~90ms (40ms Turbo), making voice agents feel genuinely conversational. Adds 40+ languages, instant cloning from 10 seconds, and auto emotion. Ideal for real-time voice.

Features

Sonic TTS models
SSM-based engine delivering ~90ms time-to-first-audio (40ms on Turbo)

Streaming API
Audio streams as it generates via WebSocket, so speech starts near-instantly

Instant voice cloning
Clone any voice from just 10 seconds of audio

Multilingual Support
Native-speaker-quality localization across 40+ languages

Automatic emotion
Interprets transcript subtext and inserts non-verbal cues like laughter

Line agent platform
Tooling to build and deploy full voice agents combining Sonic and Ink STT

Pros and Cons

What Works Well
  • Lowest latency in the market (sub-100ms, 40ms Turbo)
  • Topped Artificial Analysis leaderboard on Sonic 3.5 launch
  • Instant cloning from just 10 seconds of audio
  • Efficient SSM architecture scales well under load
WHAT could be better
  • Developer-only, no consumer studio or no-code UI
  • Voice cloning locked behind paid Pro tier
  • Fewer languages than ElevenLabs for long-form narration quality

Pricing Plans

Pro (Monthly)
$ 5
per month
Startup (Monthly)
$ 49
per month
Scale (Monthly)
$ 299
per month
Enterprise
Custom
Contact for Pricing

Customers

  • Developers building real-time conversational voice agents
  • Contact-center and customer-service automation teams
  • Game studios voicing responsive, real-time NPCs
  • AI companion and avatar builders
  • Enterprises needing sub-100ms speech at scale

Company Information

Company Name
Cartesia
Company Founded Year
2023
Company Location
San Francisco, California, USA

Frequently Asked Questions

How low is Cartesia’s latency?
Sonic delivers around 90ms time-to-first-audio, with a Turbo variant at roughly 40ms, designed so voice agents feel conversational rather than laggy.
Is commercial use included on the free plan?
No. The commercial-use license begins at the Pro tier ($5/mo); Free is for prototyping and testing.
When can I clone voices, and how much audio is needed?
Instant voice cloning (from about 10 seconds of audio) is available from the Pro tier. Professional voice cloning unlocks at the Startup tier.
How many languages does Sonic support?
40+ languages with native-speaker-quality voices.
Can I deploy on-premise or in a private cloud?
On-prem/VPC deployment is handled through Enterprise; Cartesia’s pricing page directs these requests to sales.
What model architecture makes it fast?
Sonic is built on State Space Models (SSMs) rather than transformers, which lets it stream audio as it generates and keeps latency low.
Does it support voice agents, not just TTS?
Yes. ‘Line’ is Cartesia’s platform for building voice agents combining Sonic (TTS) and Ink (STT); agent calls are billed per minute (around $0.06/min).

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