Cartesia

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Power voice agents with sub-100ms TTS that streams in real time. Sonic's architecture eliminates the latency pause that makes voice bots feel robotic.

Audio

★ 4.6(1,400 reviews)freemium

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Overview

Cartesia is a real-time voice AI platform built on Sonic — a state-space model architecture that delivers sub-100ms text-to-speech latency, making natural conversational AI and live voice agents practical. Unlike autoregressive TTS models that generate audio sequentially, Sonic streams output as it processes input, eliminating the turn-taking pause that makes voice bots feel robotic. Used in production by voice AI products that need human-paced conversation.

Key Features

Sub-100ms time-to-first-audio for real-time voice applications
Streaming TTS — output starts before the full text is processed
50+ voices across accents and languages
Voice cloning from a short audio sample
Emotion and pacing control via SSML-style tags
WebSocket API for low-latency real-time integration

Pros

• Fastest TTS latency available — essential for conversational voice agents
• Streaming architecture enables natural back-and-forth conversation pacing
• Voice quality is competitive with ElevenLabs at significantly lower latency

Cons

• Premium voice quality still trails ElevenLabs on richness and nuance
• Voice cloning requires more audio samples than some competitors
• Growth plan pricing scales steeply with volume