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Cartesia vs Phonic

A side-by-side comparison of Cartesia and Phonic, two Voice tools, drawn from Ignaite's continuously-verified listings.

Compared from listings verified as of

Cartesia

Voice

Low-latency streaming text-to-speech for real-time voice.

View Cartesia

Phonic

Voice

Speech-to-speech platform for reliable voice agents.

View Phonic

At a glance

Feature comparison of Cartesia and Phonic
AttributeCartesiaPhonic
CategoryVoiceVoice
Pricing (differs)FREEMIUMPAID
LicenseProprietaryProprietary
DeploymentCloudCloud
Platforms (differs)APIAPI, Web
Model support (differs)Single model (proprietary)Self-contained (on-device)
Vendor (differs)CartesiaPhonic
Capabilities (differs)
  • Voice agent
  • Speech synthesis (TTS)
  • Transcription (STT)
  • Voice cloning
  • Voice agent
  • Tool / function calling
  • LLM evaluation
  • LLM observability

The honest brief

Cartesia

State-space Sonic models hit sub-100ms first audio — the latency floor for real-time voice agent loops.

  • Streaming over WebSocket for fast first audio
  • State-space architecture, not transformer
  • Streaming-first WebSocket protocol depth
  • Cost-competitive at scale
  • Long-form expressive texture trails ElevenLabs
  • Fewer voices than ElevenLabs catalog
  • API-only, no end-user app

Phonic

Runs one proprietary speech-to-speech model at sub-300ms latency instead of an STT→LLM→TTS chain, with eval and observability built in for voice agents.

  • Reliable tool calling for voice agents
  • Natural turn-taking, low latency
  • Built-in eval and observability
  • Self-host / containerized option
  • Enterprise-focused, no public free tier
  • Pricing not published
  • Younger than larger voice platforms

When to pick which

Both cover Voice agent.

Pick Cartesia if you need Speech synthesis (TTS), Transcription (STT), and Voice cloning.

  • Speech synthesis (TTS) (primary capability)
  • Transcription (STT) (secondary capability)
  • Voice cloning (secondary capability)

Pick Phonic if you need Tool / function calling, LLM evaluation, and LLM observability.

  • Tool / function calling (secondary capability)
  • LLM evaluation (secondary capability)
  • LLM observability (secondary capability)

Phonic leans on Voice agent as a headline capability; Cartesia treats it as secondary.

  • Voice agent (primary capability)

They also differ on:

Pricing
FREEMIUM · PAID
Platforms
API · API, Web
Model support
Single model (proprietary) · Self-contained (on-device)
Cartesia detailsPhonic detailsAll Voice apps