Cartesia vs Soniox
Listeners rate Cartesia's Sonic 3.6 above Soniox text to speech.
ServiceNow, Decagon, and Quora run their production voice agents on Cartesia, the voice listeners rate first on independent blind tests.
Voice quality
Listeners rate Sonic 3.6 above Soniox TTS
- Artificial Analysis plays listeners two clips of the same line without naming the model, and rates every model on the board the same way.
- Sonic 3.6 leads Soniox TTS Real-Time v2 by nearly 100 points.
Provider Voice Arena Elo
Higher is better
Speed
Sonic 3.6 generates speech six times as fast as Soniox TTS
- Artificial Analysis times every model on the board with the same harness, in characters generated per second.
- Sonic 3.6 generates 114.9 characters per second, against 18.0 for Soniox TTS Real-Time v2.
Characters per second
Higher is better
Reasons why companies choose Cartesia over Soniox
Human-like naturalness
Intonation, pacing, pronunciation, emotion, and audio quality that drive higher completion rates
Cartesia1275 EloSoniox1176 EloSeptember 2026
Speed
Headroom over playback, so a long turn never stalls mid-sentence.
Cartesia114.9 characters per secondSoniox18.0 characters per secondSeptember 2026
Frequently asked questions
How is the quality score measured?
It comes from Artificial Analysis, an independent benchmark. Listeners hear two clips of the same line without being told which model produced either, and pick the one they prefer. Sonic 3.6 rates above Soniox TTS Real-Time v2, Soniox's current text to speech model.
How fast does Cartesia generate speech compared with Soniox?
Artificial Analysis measures Sonic 3.6 at 114.9 characters per second and Soniox TTS Real-Time v2 at 18.0, timed by the same harness. That headroom over playback keeps a long turn from stalling mid-sentence.
Can I use Cartesia for speech while keeping another transcription provider?
Yes. Sonic is a standalone speech API, so it drops into the major voice agent platforms beside whichever transcription and language model you already run.
How long does it take to switch from Soniox?
One to two weeks for most teams. Cartesia is integrated into the major voice agent platforms and every model is on the public API, so there is no platform to move onto and nothing to unpick later.
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