Cartesia vs OpenAI
Listeners rate Cartesia ahead of OpenAI's Realtime model.
Cartesia gives you the voice listeners picked, with first audio in under 90ms, voice cloning from 10 seconds, and deployment inside your own network.
Voice quality
Listeners prefer Sonic 3.6 over GPT-Realtime-2
- The Provider Voice Arena rates every model on its own voices, so a catalogue counts alongside the acoustics.
- Sonic 3.6 leads GPT-Realtime-2 there by more than 200 Elo points.
Provider Voice Arena Elo
Higher is better
Price
Cartesia costs a quarter of what the Realtime model does
- Artificial Analysis prices every model on the board the same way, per million characters of text.
- The cheaper model here is also the one listeners rate higher, so the saving does not come out of quality.
Price per 1M characters
USD, lower is better
Reasons why companies choose Cartesia over OpenAI
Human-like naturalness
Intonation, pacing, pronunciation, emotion, and audio quality that drive higher completion rates
Cartesia1282 EloOpenAI1070 EloAugust 2026
Custom voices
How much audio it takes, and who is allowed to use one.
CartesiaInstant clone from 10 seconds, professional clone from 30 minutesOpenAICustom voices are limited to eligible customers and arranged through salesDeployment
Decides whether regulated teams can use it at all.
CartesiaVPC, on-prem, on-device, or air-gapped, backed by a 99.9% uptime SLAOpenAIHosted API onlyEnd-to-end stack
How many vendors it takes to run one call.
CartesiaTTS, STT, and Agents from one vendor, on one APIOpenAITTS and Realtime speech-to-speech
Frequently asked questions
How much does the OpenAI Realtime API cost?
GPT-Realtime-2 lists at $32 per million audio input tokens ($0.40 cached) and $64 per million audio output tokens, plus $4 and $24 per million text tokens. GPT-Realtime-2.1 lists at the same rates. Artificial Analysis prices GPT-Realtime-2 speech at $191.60 per million characters and Sonic 3.6 at $49, about a quarter as much.
Which OpenAI model does this compare against?
GPT-Realtime-2, the speech model behind the OpenAI Realtime API, which Artificial Analysis lists under that name on its Provider Voice Arena. It is the model most teams reach for when they build a voice agent on an OpenAI stack.
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. On the Provider Voice Arena, where every model speaks in its own voices, Sonic 3.6 rates 1278 and GPT-Realtime-2 rates 1077.
Can I use my own voice with Cartesia?
Yes. An instant clone takes 10 seconds of audio and a professional clone takes 30 minutes. Both are self-serve, rather than arranged case by case.
How long does it take to switch from the OpenAI Realtime API?
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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