Cartesia vs Speechify
Listeners rate Cartesia's Sonic 3.6 above every Speechify model.
ServiceNow, Decagon, and Quora run their production voice agents on Cartesia. One model, 44 languages, and voice cloning on the public API.
Voice quality
Listeners rate Sonic 3.6 above every Speechify model
- 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 rates above both Simba models, and more than 150 points above Simba 3.0.
Provider Voice Arena Elo
Higher is better
Accuracy
Sonic 3.6 makes fewer word errors than both Simba models
- Coval transcribes every clip each model generates and compares it with the script, so a lower rate means more of the script is spoken as written.
- Sonic 3.6 misreads fewer words than Simba 3.0 and Simba 3.2, so names, numbers, and codes come through as written.
Word error rate
Lower is better
Consistency
Sonic 3.6 holds steadier latency from call to call
- Coval times every request to first audio. The standard deviation measures how far response times swing from one call to the next.
- Sonic 3.6 swings less than either Simba model, so the slow calls stay close to the typical one.
Latency standard deviation
Time to first audio; lower is better
Reasons why companies choose Cartesia over Speechify
Human-like naturalness
Intonation, pacing, pronunciation, emotion, and audio quality that drive higher completion rates
Cartesia1275 EloSpeechify1239 EloSimba 3.21121 EloSimba 3.0September 2026
Accuracy
Whether names, numbers, and terms come through as written.
Cartesia1.99% word error rateSpeechify2.10% word error rateSimba 3.02.73% word error rateSimba 3.2September 2026
Consistency
At scale, the spread in latency matters more than the average.
CartesiaResponse times stay tightly clustered (σ = 60ms)Speechifyσ = 154msSimba 3.0σ = 234msSimba 3.2September 2026
Languages
Comprehension and trust across a global customer base.
Cartesia44 languages from one model, with native accentsSpeechifyEnglish only on Simba 3.2, 6 languages on Simba 3.0
Frequently asked questions
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