Cartesia

Cartesia was founded by Karan Goel, Arjun Desai, Brandon Yang, Albert Gu, and Chris Re, several of whom are the researchers behind state space models (SSMs) and Mamba, the architecture that underpins the company's products. Albert Gu (now at Carnegie Mellon) and Tri Dao pioneered Mamba, and Cartesia's models are built on derivatives of that work. The company positions itself as building the real-time intelligence layer for voice AI, with its flagship Sonic model reported to be used by over 10,000 customers including Quora, Cresta, and Rasa.

Cartesia's core product is the Sonic text-to-speech model family (Sonic 3 and Sonic 3.5), delivered via REST and WebSocket streaming APIs and SDKs. Key capabilities include 40-90ms claimed time-to-first-audio, consistent low latency even at P99 due to the SSM architecture, a library of 600+ voices across 42 languages, instant and pro voice cloning, and fine-grained control over speed, volume, and emotion (including features like AI laughter and expressive delivery). The platform is API-first with no self-hosted, mobile app, or browser extension offering, and is designed to plug into voice agent stacks such as Vapi and LiveKit.

Cartesia primarily serves developers, AI/ML engineers, and product teams at startups and enterprises building latency-sensitive voice applications: conversational voice agents, phone/IVR automation, customer support, dubbing and localization, narration, and accessibility tools. Its emphasis on real-time streaming and P99 latency consistency makes it especially attractive to teams shipping live, interactive voice experiences at scale.

Cartesia raised a $27M seed round in December 2024, a $64M Series A led by Kleiner Perkins in March 2025, and a $100M round in November 2025 from Kleiner Perkins, Index Ventures, Lightspeed, and NVIDIA, totaling roughly $191M in disclosed funding.